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# From the Big Dry to the Holocene in Eastern Africa and beyond

Joséphine Lesur, Jessie Cauliez, Lamya Khalidi, Laurent Bruxelles, Isabelle

Crevecoeur, David Pleurdeau, Chantal Tribolo, François Bon

► To cite this version:

Joséphine Lesur, Jessie Cauliez, Lamya Khalidi, Laurent Bruxelles, Isabelle Crevecoeur, et al. From the Big Dry to the Holocene in Eastern Africa and beyond. Séances de la Société préhistorique française, 20, 2023. hal-04789406

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DU BIG DRY À L'HOLOCÈNE
EN AFRIQUE DE L'EST ET AU-DELÀ

FROM THE BIG DRY TO THE HOLOCENE
IN EASTERN AFRICA AND BEYOND
Les « Séances de la Société préhistorique française »
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Illustrations de couverture : Bassin oriental du lac Abhé à Djibouti -
Territoire de réflexion sur la transition chasseurs-cueilleurs/premiers éleveurs dans la Corne de l'Afrique (© J. Cauliez)

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© Société préhistorique française, Paris, 2023.
Tous droits réservés, reproduction et diffusion interdite sans autorisation.

Dépôt légal : 4e trimestre 2023

ISSN: 2263-3847 – ISBN: 2-913745-93-8 (en ligne) - EAN: 9782913745933
DU BIG DRY À L'HOLOCÈNE
EN AFRIQUE DE L'EST ET AU-DELÀ

FROM THE BIG DRY TO THE HOLOCENE
IN EASTERN AFRICA AND BEYOND

ACTES DE LA SÉANCE DE LA SOCIÉTÉ PRÉHISTORIQUE FRANÇAISE

TOULOUSE

25-28 SEPTEMBRE 2019

Textes publiés sous la direction
de Joséphine LESUR, Jessie CAULIEZ, Lamya KHALIDI,
Laurent BRUXELLES, Isabelle CREVECOEUR, David PLEURDEAU,
Chantal TRIBOLO et François BON

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CONTENTS / SOMMAIRE

Isabelle CREVECOEUR, Marie MATU, Marie-Hélène DIAS-MEIRINHO, Priscilla BAYLE, Osbjorn PEARSON..................................................9

Human Evolution and Population Dynamics

in Northeast Africa at the End of the Pleistocene and the Beginning of the Holocene

Évolution humaine et dynamiques de population dans le nord-est africain à la fin de Pléistocène
et au début de l'Holocène

Alice LEPLONGEON, Katja DOUZE, Behailu HABTE, Lamya KHALIDI,

Clément MÉNARD, David PLEURDEAU, François BON..................................................................................................................35

A Comparative Look at Technical Traditions in the Horn of Africa and the Nile Valley
at the End of the Pleistocene

Regards croisés sur les traditions techniques dans la Corne de l'Afrique et dans la vallée du Nil
à la fin du Pléistocène

Ralf VOGELSANG..................................................................................................................................................................................71

Living the High Life? Prehistoric Occupation of High-Altitude Environments in Ethiopia

Une vie de haute volée ? L'utilisation des environnements de haute montagne en Éthiopie

Isabelle CREVECOEUR, Marie-Hélène DIAS-MEIRINHO, Antoine ZAZZO, Daniel ANTOINE, François BON..................................................91

Interpersonal Violence in the Late Pleistocene

A Comprehensive Reanalysis of the Nile Valley Cemetery of Jebel Sahaba

Violences interpersonnelles durant le Pléistocène supérieur

Réévaluation du cimetière de Jebel Sahaba

Béatrix MIDANT-REYNES, François BRIOIS, Tiphaine DACHY ..................................................................................................................125

A Singular Story between Deserts and the Nile

The Egyptian Path toward Food Production

Une histoire singulière entre déserts et Nil

La trajectoire égyptienne vers l'économie de production

Els CORNELISSEN..................................................................................................................................................................................137

Challenges and opportunities during the Last Glacial Maximum at the forest margins in Central Africa

Défis et opportunités aux abords de la forêt tropicale à la fin du Pléistocène en Afrique centrale
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Du Big Dry à l'Holocène en Afrique de l'Est et au-delà

*From the Big Dry to the Holocene in Eastern Africa and beyond*

Actes de la séance de la Société préhistorique française de Toulouse (septembre 2019)

Textes publiés sous la direction de Joséphine Lesur, Jessie Cauliez, Lamya Khalidi,

Laurent Bruxelles, Isabelle Crevecoeur, David Pleurdeau, Chantal Tribolo et François Bon
Paris, Société préhistorique française, 2023

(Séances de la Société préhistorique française, 20), p. 9-10

www.prehistoire.org

ISSN : 2263-3847 – ISBN : 2-913745-93-8

Avant-propos

J. LESUR, J. CAULIEZ, L. KHALIDI, L. BRUXELLES,
I. CREVECOEUR, D. PLEURDEAU, C. TRIBOLO et F. BON

La présente publication réunit un ensemble de contributions issues de la séance d'automne de la Société préhistorique française, qui s'est tenue à Toulouse au mois de septembre 2019 et qui avait pour intitulé *Dynamiques culturelles et transformation des paysages dans un continent en mutation : du Big Dry à l'Holocène dans l'Est africain*.

En Afrique de l'Est, que l'on s'interroge sur les mécanismes qui sous-tendent les changements technologiques, cultu-
rels, sociaux ou économiques des sociétés humaines et des populations qui les composent, ou bien au contraire que l'on
constate leur persistance, les conditions environnementales sont souvent mises en avant. Dans le contexte de la Préhistoire
récente, on assigne par exemple à l'écologie et au climat un rôle majeur dans le maintien des économies de prédation ou, à
l'inverse, dans l'émergence de la domestication animale et végétale et donc l'adoption de nouveaux modes d'alimentation
par les sociétés humaines.

Pour mieux comprendre le rôle de l'écologie et du climat dans les trajectoires socioculturelles humaines, nous avons
porté notre attention sur les dynamiques culturelles des sociétés et leur relation avec les transformations environnemen-
tales et paysagères entre les vallées du Nil et du Rift est-africain, depuis la fin du Pléistocène à l'Holocène récent, en
commençant par une phase froide et aride dénommée « Big Dry », ou Dernier Maximum glaciaire (LGM). Cette période,
qui s'est déroulée entre environ 29 ka et 19 ka, a entraîné l'extension des zones désertiques, l'abaissement du niveau des
mers et des lacs et la réduction du couvert végétal. La vallée du Rift livre peu de sites pour cette période, ce qui suggère
des refuges de population dans des écozones plus idéales, comme cela semble être le cas dans la vallée du Nil, ou bien
l'effacement des traces à la suite de phénomènes d'érosion contemporains ou postérieurs à cet épisode climatique. Des
conditions plus humides s'installent partout pendant la période humide africaine (~ 15 ka-5 ka), accompagnées d'une aug-
mentation de sites de chasseurs-cueilleurs, mais l'on constate là encore des contrastes assez forts dans les enregistrements
que fournissent ces deux contextes géographiques. Entre le neuvième et le premier millénaire BP, les premières transitions
vers la production alimentaire et la domestication animale commencent à se produire dans ces mêmes vallées, mais selon
là encore des rythmes et des enregistrements très différents.

En raison de la mosaïque des écosystèmes disponibles, des géographies et des topographies diverses dans ces régions
– des montagnes de haute altitude et leurs forêts arbustives aux plaines désertiques ou encore aux milieux lacustres et
marins –, les sociétés ont adopté des stratégies d'adaptabilité polymorphes. Ces transitions se sont produites avec des
décalages chronologiques importants selon les régions. De même, de nettes divergences dans les innovations techniques
sont observées, mettant en évidence des trajectoires différentes de sociétés qui ont pu être connectées à certaines époques
et isolées à d'autres, et dont la subsistance et la mobilité ont été partiellement adaptées à l'évolution des paysages – pay-
sages affectés eux-mêmes par des changements hydro-climatiques d'amplitudes contrastées. Avec le passage progressif
à des économies alimentaires plus diversifiées, s'ajoute encore la question de l'accumulation et du stockage des denrées
alimentaires, partiellement facilités par les conditions environnementales et les ressources. On peut ainsi voir se mettre en
place des pratiques secondaires de l'élevage chez des sociétés semi-sédentaires tournées vers la pêche et dans des sociétés
chasseurs-cueilleurs avec différents degrés de mobilité.

Les nouvelles données archéologiques et environnementales des vallées du Rift est-africain et du Nil et au-delà, qui sont rassemblées dans cette session, démontrent, sur fond de biodiversité environnementale, la pluralité des stratégies de subsistance économique et des dynamiques de peuplement qui se produisent de manière arythmique à travers le continent au cours de cette période. À travers les contributions réunies ici, nous assistons au changement sociétal et à la transfor-
mation du paysage à travers différents prismes, ceux du climat et de l'environnement comme ceux de l'économie, de la démographie, des traditions techniques et des expressions culturelles humaines. Ce numéro offre une exploration des multiples expressions de ces modifications ainsi qu'une fenêtre sur les changements des anthroposystèmes dynamiques à travers le continent africain.

La première partie de ce volume est consacrée aux dynamiques culturelles et à la transformation paysagère du Big Dry à travers des travaux conduits actuellement dans les vallées du Nil et du Rift est-africain. La seconde porte sur la présentation de grandes synthèses régionales permettant d'élargir la thématique à l'échelle du continent africain.

L'ensemble de la publication est un hommage à notre collègue le professeur X. Gutherz, pour ses contributions majeures à l'archéologie et à la préhistoire de la Corne de l'Afrique.

Nous tenons à remercier la Société préhistorique française pour l'édition et la publication de ce volume. Tous nos remerciements vont également à l'université de Toulouse Jean-Jaurès qui a accueilli cette manifestation, aux UMR 5199 (PACEA), 5608 (TRACES), 6034 (Archéosciences Bordeaux), 7194 (HNHP), 7209 (AASPE), 7264 (CEPAM) ainsi qu'à l'Agence nationale de la recherche (ANR-14-CE31), au projet UCA JEDI (ANR-15-IDEX-0), au LabEx LaScArBx-AAP5-2015 (université de Bordeaux), à la commission des fouilles du ministère de l'Europe et des Affaires étrangères (MEAE), au label Site d'étude en écologie globale (SEEG) de l'INEE CNRS, à l'ambassade de France auprès de la république de Djibouti, à l'Institut des déserts et des steppes, au ministère de l'Enseignement supérieur et de la Recherche djiboutien et à l'Institut de recherches archéologiques et historiques (IRAH) de Djibouti, au Centre français des études éthiopiennes (CFEE), à l'Ethiopian Authority for Research and Conservation of Cultural Heritage (ARCCH), à l'Afar Bureau for Tourism and Culture et à l'IRP ABASC (CNRS-INEE) pour leur soutien financier dans la réalisation de ce volume et dans la conduite des projets archéologiques dans la vallée du Nil et la Corne de l'Afrique dont plusieurs des résultats sont présentés ici.
Du Big Dry à l'Holocène en Afrique de l'Est et au-delà
From the Big Dry to the Holocene in Eastern Africa and beyond
Actes de la séance de la Société préhistorique française de Toulouse (septembre 2019)
Textes publiés sous la direction de Joséphine Lesur, Jessie Cauliez, Lamya Khalidi, Laurent Bruxelles, Isabelle Crevecoeur, David Pleurdeau, Chantal Tribolo et François Bon Paris, Société préhistorique française, 2023
(Séances de la Société préhistorique française, 20), p. 11-12
www.prehistoire.org
ISSN : 2263-3847 - ISBN : 2-913745-93-8

## Foreword

J. LESUR, J. CAULIEZ, L. KHALIDI, L. BRUXELLES,
I. CREVECOEUR, D. PLEURDEAU, C. TRIBOLO et F. BON

This publication brings together a number of contributions from the autumn session of the Société Préhistorique Française conference entitled *Cultural dynamics and landscape transformation in a rapidly changing continent: from the Big Dry to the Holocene in Eastern Africa, that took place in Toulouse in September 2019*.

In Eastern Africa, environmental conditions are often put forward to explain the mechanisms underlying technological, cultural, social or economic changes in human societies and the populations that make them up, or, on the contrary, their persistence. In the context of recent prehistory, ecology and climate are believed to have played a major role in enduring predation-based economies for example, or, conversely, in the emergence of animal and plant domestication and thus the adoption of new foodways by human societies.

To better understand the role of ecology and climate in human socio-cultural trajectories, we focused our attention on the cultural dynamics of societies and their relation to environmental and landscape transformations in the Nile and the East African Rift valleys, from the end of the Pleistocene to the Late Holocene, starting with a major cold and arid period known as the 'Big Dry' or Last Glacial Maximum (LGM). This period occurred between ~ 29 ka and 19 ka and led to the extension of desertic zones, the lowering of sea and lake levels and the reduction of vegetation cover. The Rift valley has yielded few sites for this period, suggesting population refugia into more ideal ecozones, as seems to have been the case in the Nile valley, or the erasure of archaeological evidence as a result of erosive phenomena that occurred contemporary with or subsequent to this climatic episode. Milder and wetter conditions were established everywhere during the African Humid Period (~ 15 ka-5 ka), accompanied by an increase in hunter-gatherer sites, but here again, we find strong contrasts in the records provided by these two geographic contexts. Between the ninth and first millennia BP, the first transitions towards food production and animal domestication began to occur in these same valleys, once again at very different rhythms and in very different ways.

Due to the mosaic of available ecosystems and the diverse geographies and topographies of these regions, from high altitude mountains and scrub forest, to desertic plains and lacustrine and marine environments, societies adopted polymorphic adaptability strategies. These transitions occurred at considerably different periods of time, depending on the region. Similarly, clear divergences in technical innovations are observed, highlighting the different trajectories of societies that may have been connected at certain times and isolated at others and whose subsistence and mobility was partially adapted to changing landscapes affected by hydroclimatic shifts of contrasting amplitude. With the gradual transition to more diversified food production economies, the accumulation and storage of foodstuffs, partially influenced by environmental conditions and resources, becomes a central question. We observe the emergence of secondary husbandry practices in semi-sedentary societies relying on fishing, as well as in hunter-gatherer societies with different degrees of mobility.

New archaeological and environmental data from the East African Rift and Nile valley regions and beyond, which are brought together in this session, demonstrate the plurality of economic subsistence strategies and settlement dynamics that occured arhythmically across the continent during this period, against a backdrop of environmental biodiversity. Through the many contributions presented here, we witness societal change and landscape transformation through different prisms, including those of climate and environment, but also those of economy, demography, technical traditions and human cultural expressions. This issue provides a rare exploration of the multiple expressions of these transformations as well as a window into the changes in dynamic anthroposystems across the African continent.
The first part of this volume focuses on cultural dynamics and landscape transformation from the Big Dry to the Holocene by treating archaeological work currently carried out in the Nile Valley and the East African Rift. The second part focuses on the presentation of regional syntheses to enlarge the theme to the scale of the African continent.

The entire publication is a tribute to our colleague, Professor X. Gutherz for his major contributions to the archaeology and prehistory of the Horn of Africa.

We would like to thank the Société Préhistorique française for editing and publishing this volume and the Université de Toulouse Jean Jaurès for hosting the conference which led to this publication. We also thank a number of institutions and agencies for having funded this volume and supported the archaeological programs in the Nile Valley and the Horn of Africa whose results are presented here, including: UMR 5199 (PACEA), 5608 (TRACES), 6034 (Archéosciences Bordeaux), 7194 (HNHP), 7209 (AASPE), 7264 (CEPAM), l'Agence Nationale de la Recherche (ANR-14-CE31) and the UCA JEDI (ANR-15-IDEX-0) Project, the LabEx LaScArBx-AAP5-2015 (Université de Bordeaux), the Ministère de l'Europe et des Affaires Étrangères (MEAE), the Site d'Étude en Écologie Globale (SEEG) of the INEE CNRS, the French Embassy in the Republic of Djibouti, the Institut des Déserts et des Steppes, the Ministère de l'Enseignement Supérieur et de la Recherche djiboutien, the Institut de Recherches Archéologiques et Historiques (IRAH) of Djibouti, the Centre Français des Études Éthiopiennes (CFEE), the Ethiopian Authority for Research and Conservation of Cultural Heritage (ARCCH), the Afar Bureau for Tourism and Heritage, and the IRP ABASC (CNRS-INEE).
Du Big Dry à l'Holocène en Afrique de l'Est et au-delà
From the Big Dry to the Holocene in Eastern Africa and beyond

Actes de la séance de la Société préhistorique française de Toulouse (septembre 2019)
Textes publiés sous la direction de Joséphine Lesur, Jessie Cauliez, Lamya Khalidi,
Laurent Bruxelles, Isabelle Crevecoeur, David Pleurdeau, Chantal Tribolo et François Bon

Paris, Société préhistorique française, 2023
(Séances de la Société préhistorique française, 20), p. 13-38

www.prehistoire.org

ISSN : 2263-3847 – ISBN : 2-913745-93-8

Human Evolution and Population Dynamics
in Northeast Africa at the End of the Pleistocene
and the Beginning of the Holocene

Évolution humaine et dynamiques de population
dans le nord-est africain à la fin de Pléistocène
et au début de l'Holocène

Isabelle CREVECOEUR, Marie MATU, Marie-Hélène DIAS-MEIRINHO,
Priscilla BAYLE, Osbjorn PEARSON

**Abstract:** Although subjected to growing interest, the debates related to *Homo sapiens'* evolution in Africa during the Late Pleistocene and the beginning of the Holocene are currently mainly tied to the success of palaeogenetic studies of Holocene skeletons from sub-Saharan Africa. These genetic results have opened new perspectives pertaining the origin of present-day African diversity and the nature of such diversity in the past, confirming previous assumptions based on the study of African fossils suggesting deep sub-structuration of human populations.

In Northeast Africa, the end of the Late Pleistocene and the beginning of the Holocene were marked by major climatic changes whose effects on human settlements are still poorly understood. Geological evidence support generally dry conditions during the Last Glacial Maximum followed by the so-called African Humid Period which ends abruptly with the second half of the Holocene and the onset of more arid conditions. In parallel with these climatic fluctuations, this transitional period witnessed the emergence of new subsistence strategies with the introduction of pastoralism.

However, the scarcity of human remains in northeast Africa has limited our understanding of modern human diversity and population
processes during this transitional period. Through a review of the key human fossils and assemblages associated to the Late Pleistocene
and the Early Holocene period in Egypt, Sudan, Ethiopia, Somalia and the Republic of Djibouti, this contribution aims at discussing
phenotypic and cultural diversity, addressing hypotheses of population isolation, replacement and/or continuity.

**Keywords:** Phenotypic diversity, Late Pleistocene, Early Holocene, Nile Valley, Horn of Africa, populations processes, adaptation, environmental changes.

**Résumé :** Bien que soumis à un intérêt croissant, les débats concernant l'évolution d'*Homo sapiens* en Afrique durant le Pléistocène supérieur et le début de l'Holocène sont actuellement principalement liés au succès des études paléogénétiques sur des squelettes holocènes d'Afrique sub-saharienne. Ces résultats génétiques ont ouvert de nouvelles perspectives concernant l'origine de la diversité africaine actuelle et la nature de cette diversité dans le passé, confirmant les hypothèses antérieures fondées sur l'étude des fossiles africains, suggérant une sous-structuration profonde des populations humaines sur ce continent depuis le Pléistocène moyen.

En Afrique du nord-est, la fin du Pléistocène supérieur et le début de l'Holocène ont été marqués par des changements climatiques
majeurs dont les effets sur populations humaines sont encore mal connus. Les données géologiques indiquent des conditions environne-
mentales plutôt arides pendant le dernier maximum glaciaire, suivies à partir de 15000 ans de la période humide africaine qui se termine
abruptement avec la seconde moitié de l'Holocène et le retour de conditions plus arides. Parallèlement à ces fluctuations climatiques,
cette période de transition a vu l'émergence de nouvelles stratégies de subsistance avec notamment l'introduction du pastoralisme.
Cependant, la rareté des restes humains en Afrique du nord-est a limité notre compréhension de la diversité phénotypique des populations à l'origine de la diversité actuelle, et des processus démographiques qui ont structuré cette diversité durant cette période de transition. À travers un examen des principaux fossiles et échantillons de populations, associés à la fin du Pléistocène supérieur et au début de l'Holocène en Égypte, au Soudan, en Éthiopie, en Somalie et en République de Djibouti, cette contribution vise à discuter de la diversité phénotypique et culturelle de ces derniers groupes de chasseurs-pêcheurs-cueilleurs, en abordant les hypothèses d'isolement, de remplacement et/ou de continuité populationnelle.

**Mots-clés** : diversité phénotypique, Pléistocène supérieur, Holocène, vallée du Nil, Corne de l'Afrique, dynamique de peuplement, adaptation, changements environnementaux.

# 1. NORTHEAST AFRICA PHENOTYPIC DIVERSITY DURING THE LATE PLEISTOCENE

The African Late Pleistocene fossil record is extremely sparse for the period that is supposed to have witnessed modern human diversification in Africa and diversions outside the African continent (Grine, 2016). Archaeological sites with human remains attributed to the first half of the Late Pleistocene (i.e. MIS 5, 130-71 ka; Lisiecki and Raymo, 2005) are essentially located in North Africa (Dar-es-Soltan II and La Grotte des Contrebandiers in Morocco; e.g. Vallois and Roche, 1958; Debénath, 1976 and 2000; Ferembach, 1976 and 1998), East Africa (Ngaloba and Eyasi in Tanzania, Panga ya Saidi in Kenya and Aduma in Ethiopia; Magori and Day, 1983; Mehlman, 1987; Haile-Selassie et al., 2004; Martinón-Torres et al., 2021), and South Africa (Blind River, Blombos and Sea Harvest; e.g. Grine and Kein, 1993; Henshilwood et al., 2001; Grine and Henshilwood, 2002; Wang et al., 2008). Even if we add to the list the sites with a wider chronological range, for which the associated human remains can be dated from at least the marine oxygen-isotope stages (MIS) 5 to 4 (black and full green dots from figure 1; for discussion about their dating see Grine, 2016), the fossil record from the first half of the Late Pleistocene is mostly documented by fragmentary human remains (incomplete cranial remains, isolated teeth or infra-cranial fragments). Comparative morphometric studies of these fossils have delivered partial information about past modern human diversity during this period. The results suggest a high level of phenotypic diversity with the persistence of plesiomorphic features in some specimens (e.g. Rightmire and Deacon, 1991; McCrosin, 1994; Pearson et al., 1998; Royer et al., 2009; Harvati and Hublin, 2012; Hublin et al., 2012), while others are described as fully modern (e.g. De Villiers, 1973; Grine and Klein, 1985; Bräuer and Mehlman, 1988; Bräuer and Singer, 1996). This situation limits our understanding of past modern human phenotypic diversity during this crucial period of modern human African diversification. In addition, no data exists from West and Central Africa, which together characterize the largest part of the African continent.

The situation is even worse for the second half of the Late Pleistocene until the end of the Last Glacial Maximum (i.e. from MIS 4 to MIS 2). Only four sites with

human remains are securely associated with MIS 4 (light green dots in figure 1), and seven for MIS 3 (light red dots in figure 1; for discussion about their dating see Grine, 2016). With the exception of the Nazlet Khater 2 and Hofmeyr specimens (light red stars in figure 1), these sites preserved very fragmentary human remains, some still unpublished, that have nonetheless contributed to palaeoanthropological discussions about the phenotypic diversity of past modern humans in Africa at that time (e.g. Grine, 2000; Hublin et al., 2012; Verna et al., 2013, Pleurdeau et al., 2014; Harvati et al., 2015; Willoughby et al., 2018; Reiner et al., 2017). The Nazlet Khater 2 (NK 2) skeleton from Egypt and the Hofmeyr (HOF) cranium from South Africa are the only two reasonably complete and well-dated African specimens from the MIS 4-MIS 3 interval. During MIS 2 and until the peak of the Last Glacial Maximal (~ 20 ka; Clark et al., 2009), five additional sites can be added to the African fossil record (light blue points and stars in figure 1). After 20 ka, the number of sites with human remains gradually increases until the end of MIS 2, although a large portion of the African continent remains undocumented. During the Holocene, the fossil record increases substantially, and homogenization of cranio-morphological features has been documented, particularly within sub-Saharan African populations, with its peak both during and after the Bantu expansion from 6 ka onwards (Ribot, 2011).

The paucity of human remains found in Africa from the last glacial period (MIS 4-MIS 2) is probably multifactorial. Historical factors involving unequal attention paid to specific African regions could have played a role, as well as taphonomic bias (Surovell et al., 2009). Another hypothesis relates to the intense environmental and climatic changes that occurred in Africa during this period, that may have affected human population adaptation and survival in some areas (Carto et al., 2009). From MIS 6 to the LGM, a growing amount of paleoclimatic evidence indicates increasing aridity that correlates with the onset of the northern hemisphere glaciation (e.g. deMenocal et al., 2000; Moreno et al., 2002; Battarbee et al., 2004; Carto et al., 2009). However, the climatic changes in Africa were not synchronous, and interregional differences are recorded in the timing of alternance between humid and arid conditions (Blome et al., 2012). In North Africa, the density of sites appears to be inversely correlated with the expansion of the Sahara, with the exception of the Nile Valley (Blome et al., 2012; Leplongeon et al., 2020; Leplongeon, 2021). Whatever the cause, the sparse
fossil record for the Late Pleistocene is clearly a limitation in discussing modern human evolution in Africa.

In northeast Africa, the only site with well-preserved and securely dated human remains during the MIS 3 is Nazlet Khater 2 (Egypt; Vermeersch et al., 1984; Vermeersch, 2002). It is penecontemporaneous from Hofmeyr (South Africa; Grine et al., 2007), the only other site from this time range with dated and substantial human remains. The NK 2 skeleton has been directly dated by ESR on tooth enamel fragments to 38 ± 6 ka (Crevecoeur, 2008), while the Hofmeyr skull has been dated to 36.2 ± 3.3 ka by a combination of optically stimulated luminescence and uranium-series methods (Grine et al., 2007). Both specimens are anatomically modern, but they also display cranial plesiomorphic features that put them on the brink of extant modern human African phenotypic diversity (Grine et al., 2007; Crevecoeur, 2012a). Regarding the infra-cranial remains of Nazlet Khater 2, the main characteristics express adaptation to high biomechanical strength and specialized activities (Crevecoeur, 2008 and 2012a). Together with the mining archaeological context, these results support the hypotheses of well-organised settlements and planned specialized activities in the Nile Valley during the MIS 3 (Van Peer, 1998).

The Hofmeyr specimen exhibits the greatest overall similarities to Upper Palaeolithic specimens from Europe rather than Holocene San populations from South Africa (Grine et al., 2007; Grine et al., 2010). Similarly, the Nazlet Khater 2 individual presents plesiomorphic features on the cranium and the mandible more comparable to those of Late Middle Pleistocene and early Late Pleistocene fossils than to chronologically closer recent African populations (Crevecoeur, 2008 and 2012a). However, their morphometric characteristics do not particularly draw them together. On the contrary, the two specimens appear to reflect different aspects of Late Pleistocene African phenotypic variation (Crevecoeur et al., 2009). While we can observe a community of robustness related to temporal trends compared to Holocene populations, they exhibit different morphological conformation, as illustrated by the following examples of craniofacial and inner ear morphology comparisons (fig. 2 to fig. 4). The face of NK 2 is particularly robust, with notable height and width dimensions. The projection of the two first principal components of the PCA performed on seven cranio-facial dimensions (fig. 3; for details of the analysis see Crevecoeur, 2012a) shows that the position of NK 2 is closer to Middle Pleistocene hominin and early *Homo sapiens* specimens than chronologically closer specimens. Hofmeyr occupies a transitional position between the earlier specimens and the extant population, lying closer to European Upper Palaeolithic specimens, and North African fossil samples from the end of the Late Pleistocene (LPNEA and LPNWA, < 20-11 ka). This dispersion along the first axis illustrates a temporal trend of a reduction in facial dimensions over time. The result is consistent with studies on the evolution of human craniofacial morphological variation (e.g. Enlow, 1990; Freidline et al., 2012; von Cramon-Taubadel, 2014; Bastir and Rosas, 2016). In

this regard, the position of Nazlet Khater 2 is somewhat anachronic.

Comparison of the inner ear structures of Pleistocene *Homo* have allowed the reconstruction of the phenetic and phylogenetic relationships between hominin specimens (e.g. Spoor et al., 1994 and 2003; Braga et al., 2013; Wu et al., 2014). While earlier studies have mainly focused on archaic specimens, several studies have since highlighted phenotypic variations on small regional and temporal scales, emphasizing the importance of this structure to discuss genetic distances and population affiliation in *Homo sapiens* (Spoor et al., 2003; Bouchneb and Crevecoeur, 2009; Crevecoeur et al., 2016; Ponce de León et al., 2018). Analysis of the Nazlet Khater 2 inner ear showed that it exhibits a set of labyrinthine characteristics that put it closer to European Upper Paleolithic specimens than to recent modern human populations, notably regarding the width of the anterior semicircular canal (Bouchneb and Crevecoeur, 2009; Crevecoeur et al., 2012a). On the other hand, the more recent MIS 2 specimen from Ishango 37 (ISH 37; fig. 1) showed greater affinity with the bony labyrinth morphology of the Qafzeh and Skhul (Q-S) samples (Crevecoeur et al., 2016). The characteristic that set ISH 37, apart from the recent and chronologically closer modern human samples, is the position of the cochlea together with its morphology. In addition to being more coronally oriented in the transversal plane, Ishango 37 possesses a larger cochlea basal turn (Creve-

<figure><img src="image_6.png" /></figure>

**Fig. 1** – African map with the location of human remains dated from the Marine Isotopic Stage 4 (MIS 4) to the Last Glacial Maximum (LGM) peak. The stars identify sites that are detailed in the text.

**Fig. 1** – *Carte de l'Afrique avec l'emplacement des restes humains datés depuis le stade isotopique marin 4 (MIS 4) au Dernier Maximum glaciaire (DMG). Les étoiles signalent les sites qui sont décrits dans le texte.*
<figure><img src="image_7.png" /><figcaption>**Fig. 2** – Composite picture of Hofmeyr (left) and Nazlet Khater 2 (right) cranium in frontal view.

**Fig. 2** – Image composite des crânes d'Hofmeyr (à gauche) et de Nazlet Khater 2 (à droite), en vue frontale.</figcaption></figure>

<figure><img src="image_8.png" /><figcaption>**Fig. 3** – Bivariate plot of the projection of the first and second principal component of the PCA on seven cranio-facial dimensions.
NK2 = Nazlet Khater 2, MPH = Middle Pleistocene Hominin, MPHS = Middle Pleistocene early *Homo sapiens*, QS = Qafzeh and Skhul, HOF = Hofmeyr, EUP = European Upper Palaeolithic fossils, KUB = Wadi Kubbaniya, LPNEA = Late Pleistocene specimens from north-east Africa (i.e. Jebel Sahaba and Wadi Halfa), LPNWA = Late Pleistocene specimens from north-west Africa (i.e. Taforalt and Afalou), LPSwa = Late Pleistocene from south-west Asia (i.e. Natufian; see Bocquentin, 2003), RMH = Recent modern human (here Egyptian population; see Howells, 1996). The ellipse represents 95% of the RMH variation.</figcaption></figure>

**Fig. 3** – Diagramme bivarié de la projection de la première et de la deuxième composante principale de l'ACP sur sept dimensions cranio-faciales. NK2 = Nazlet Khater 2, MPH = hominines du Pléistocène moyen, MPHS = premiers *Homo sapiens* du Pléistocène moyen, QS = Qafzeh and Skhul, HOF = Hofmeyr, EUP = fossiles *Homo sapiens* du Paléolithique supérieur européen, KUB = Wadi Kubbaniya, LPNEA = spécimens de la fin du Pléistocène supérieur du nord-est de l'Afrique (à savoir Jebel Sahaba et Wadi Halfa), LPNWA = spécimens de la fin du Pléistocène supérieur du nord-ouest de l'Afrique (à savoir Taforalt et Afalou), LPSwa = spécimens de la fin du Pléistocène supérieur d'Asie du sud-ouest (à savoir les Natoufiens ; voir Bocquentin, 2003), RMH = *Homo sapiens* récents (ici population égyptienne ; voir Howells, 1996). L'ellipse représente 95 % de la variation du group RMH.
coeur et al., 2016). F. Spoor et al. (2003) highlighted this characteristic in a smaller comparative sample consisting of Qafzeh and Skhul specimens. Similar morphologies have been observed in the Hofmeyr specimens (Creve-coeur et al., 2022). An enlarged anterior semi-circular canal, like Nazlet Khater 2, and a wide cochlea that is positioned more inferiorly with respect to the level of the lateral semi-circular canal, like Ishango 37, char-acterize the Hofmeyr inner ear. As illustrated by their position in the lower left quadrant of the first two prin-cipal component projections in figure 4, these inner ear characteristics, shared by the EUP and Q-S specimens, also influenced the position of the early Holocene fossil from Shum Laka (SE II) which exhibits a genetic signal of deep ancestry (A00 Y-chromosome lineage; Lipson et al., 2020). Located close to Qafzeh 11, this member of the Early Holocene African (EHA) comparative sample is separated from the other individual from Shum Laka (SE I), whose Y-chromosome haplogroup (B) is com-mon among recent hunter-gatherers from Central Africa. Interestingly, the similarities of Hofmeyr to Nalet Khater

or Ishango differ in relation to the part of the bony lab-yrinth investigated, namely the semi-circular canals or the cochlea. The independent physiological roles of each component of the inner ear likely imply that they could have evolved separately as noted within the Neanderthal clade (Quam et al., 2016; Conde-Valverde et al., 2019). The affinities of Hofmeyr with EUP and Q-S regarding the size and proportions of the semi-circular canals, and its similarity with Ishango based on its large cochlea could be interpreted as reflecting different paths within Late Pleistocene modern human evolution (Crevecoeur et al., 2022). Given that the strong phylogenetic signal of cochlear dimensions may be confidently used to assess biological affinities between human populations (Braga et al., 2015; Conde-Valverde et al., 2019), we believe that these results help to support the hypotheses of a certain level of phylogenetic discontinuity between Late Pleis-tocene and present-day populations, even those that are geographically proximate, within the African continent.

Despite the fragmentary nature of the Late Pleistocene
fossils, these results echo the paleogenetic hypotheses

<figure><img src="image_9.png" /><figcaption>**Fig. 4** – Bivariate plot of the projection of the first and second principal component of the PCA on fourteen variables that account for the general size and shape of the bony labyrinth. Composite image of the virtual reconstruction of Ishango, Nazlet Khater 2 and Hofmeyr bony labyrinth structure. HOF = Hofmeyr, NK2 = Nazlet Khater 2, ISH = Ishango 37, QS = Qafzeh and Skhul, EUP = European Upper Palaeolithic fossils, EHA = Early to mid-Holocene specimens from north-east and central Africa (Shum Laka, Lothagam, Gogoshiis Qabe, Hara Idé 2), RMH = Recent modern human, NEAND = Neandertal specimens (see Crevecoeur et al., 2022). The black ellipse represents 95% of the RMH variation. The pink line delimits the Q-S convex hull.</figcaption></figure>

**Fig. 4** – Diagramme bivarié de la projection de la première et de la deuxième composante principale de l'ACP sur quatorze variables rendant compte de la taille et de la forme du labyrinthe osseux. Image composite de la reconstruction virtuelle de la structure du labyrinthe osseux des fossiles d'Ishango, de Nazlet Khater 2 et d'Hofmeyr. HOF = Hofmeyr, NK2 = Nazlet Khater 2, ISH = Ishango 37, QS = Qafzeh et Skhul, EUP = fossiles Homo sapiens du Paléolithique supérieur européen, EHA = spécimens du début de l'Holocène d'Afrique du nord-est et d'Afrique centrale (à savoir Shum Laka, Lothagam, Gogoshiis Qabe, Hara Idé 2), RMH = Homo sapiens récents, NEAND = Néandertaliens (voir Crevecoeur et al., 2022). L'ellipse noire représente 95 % de la variation du groupe RMH. La ligne rose délimite le polygone convexe contenant les individus de Q-S.
about deeply divergent, geographically separated popu-
lations in Africa during the Late Pleistocene (e.g. Quin-
tana-Murci et al., 2008; Scheinfeldt et al., 2010; Schle-
busch et al., 2017; Skoglund et al., 2017; Schlebush and
Jakobsson, 2018; Lipson et al., 2020). The fossils under
study are distinct from both extant African populations
and many Holocene specimens. They exhibit diverse bio-
logical affinities with earlier Middle to Late Pleistocene
fossils and European Upper Paleolithic *Homo sapiens*
that appear related to plesiomorphic morphologies or part
of the phenotypic diversity that is no longer documented
in more recent populations. Similar observations made
for some individuals from the terminal part of the Pleisto-
cene (Crevecoeur et al., 2009; Harvati et al., 2011; Tryon
et al., 2015) suggest that deep population substructures
in Africa lasted at least until the mid-Holocene period
and that some populations might not have contributed
to present day diversity. In this regard, the metapopula-
tion model of African population history is currently the
best-fitting theory to reconcile palaeoanthropological and
ancient and recent genetic data (Scerri et al., 2019).

It is of course possible that some of the observations
made about Nazlet Khater 2, or others Late Pleistocene
fossils could be interpreted as indicating signs of admix-
ture with a “ghost archaic” population as some studies
have suggested (e.g. Harvati et al., 2011; Durvasula and
Sankararaman, 2020). However, given our poor under-
standing of African Late Pleistocene phenotypic and
genetic diversity, as well as the recent work of M. Lipson
et al. (2020) which also suggested the presence of a
“ghost modern” population input in present day variation,
we favor a conservative approach regarding these asser-
tions. The identification of admixed phenotypes is cur-
rently limited by the absence of fossils from this “ghost
archaic” population and will only be possible once Afri-
can modern human past phenotypic diversity is properly
encompassed.

## 2. NILE VALLEY POPULATION PROCESSES AT THE END OF THE PLEISTOCENE AND THE BEGINNING OF THE HOLOCENE

As described above, geological evidence points to
generally dry conditions in Africa during the Last
Glacial Maximum (LGM, ~ 23-18 ka; Gasse, 2000). The
LGM was then followed by the African Humid Period
(~ 15-5.5 ka) which ended abruptly with the second half
of the Holocene and the onset of more arid conditions
(DeMenocal et al., 2000). In the Nile Valley, climatic
conditions are depicted as hyper-arid during the second
half of the Late Pleistocene (Paulissen and Vermeersch,
1987). During the MIS 2 (27.8-14.7 ka; Sanchez Goñi
et al., 2010), the Nile Valley probably functioned as a ref-
uge for human populations. This is attested by the high
density of archaeological contexts in Upper Egypt and
Lower Nubia dated to the aridity peaks of the LGM and the
second part of the Heinrich Stadial 1 (HS1b; 16-14.5 ka;

Hoelzmann et al., 2004; Vermeersch and Van Neer, 2015; Castañeda et al., 2016; Vermeersch, 2020; Leplongeon, 2021). The Blue Nile and the White Nile were then highly seasonal rivers and the Sudd swamps had yet to develop (Williams et al., 2000, Hoelzmann et al., 2004). Around 15-14 ka, the present Nile-flow regime was re-established by the sudden overflow of lake Victoria in the White Nile, which caused severe flooding in the Nile Valley as far as Egypt (Williams et al., 2006). This period of hydrological instability was interrupted by a short-term return of drier and colder climatic condition that coincides with the Younger Dryas interval (YD; ~ 12.9-11.7 ka; Rasmussen et al., 2006). It was only after the Younger Dryas (~ 12.9-11.7 ka) that the monsoon conditions of the African Humid Period became more stable for human presence in the Nile Valley, as evidenced by the scarcity of traces of human occupation at the end of the Late Pleistocene and the beginning of the Holocene (~ 15-10.5 ka). Archaeological sites from this period are restricted to the floodplain in Upper Egypt and Lower Nubia (Nicoll, 2004; Kuper and Kröpelin, 2006; Schild and Wendorf, 2010; Vermeersch and Van Neer, 2015, Vermeersch, 2020; Leplongeon, 2021), and only a few sites have yielded complete human remains. Among these, the most emblematic are Jebel Sahaba (JS, site 117), Tushka (site 8905), Wadi Kubbaniya, and Wadi Halfa (WH, site 6B36; fig. 5; Hewes et al., 1964; Wendorf, 1968; Wendorf and Schild, 1986).

Culturally, a large variety of lithic assemblages, linked
to Late Paleolithic, or Late Stone Age, industries based
on the production of flakes and elongated products of
small dimensions, including high proportions of backed
tools (Schild and Wendorf, 2010; Leplongeon, 2021),
has been identified in sites associated with the end of the
Late Pleistocene (e.g. the Fakhurian, the Kubbaniyan, the
Idfuan, the Ballanan-Silsilian, the Afian, the Isnan and
the Qadan; Wendorf, 1968; Lubell, 1974; Wendorf et al.,
1989; Schild and Wendorf, 2010; Vermeersch, 2010). The
great variability of typological characteristics of these
lithic assemblages has led to the recognition of different
industries that seem to be regionally and chronologically
constrained, with some industries occurring only in Lower
Nubia or in Upper Egypt (Leplongeon, 2021). Archaeo-
zological analysis of these Late Pleistocene settlements
indicate similar human subsistence strategies based on
the exploitation of the Nilotic environment (Schild and
Wendorf, 2010). Seasonally adapted fishing activities,
shellfish consumption, medium and large ungulate hunt-
ing and plant tuber processing are documented at various
locations (Van Neer et al., 2000; Linseele and Van Neer,
2010; Yeshurun, 2018). In this framework of limited sub-
sistence strategy options and constrained geographical
habitable environment, the development of a wide range
of lithic cultural traditions is interesting. They don't seem
to be related to specific activities and are characterized
by distinctive sets of lithic tools and/or technology that
could be associated with small hunting-fishing-gathering
groups (Vermeersch, 2010). It has therefore been sug-
gested that each of these lithic entities could represent
<figure><img src="image_10.png" /><figcaption>**Fig. 5** – Map of the Nile Valley with the location of sites preserving human remains dated from the MIS 3 to the end of the early Holocene period (MIS 1-EH). Stars identify sites that are discussed in the text.</figcaption></figure>

<caption>**Fig. 5** – Carte de la vallée du Nil avec la localisation des sites ayant livré des restes humains datés depuis le MIS 3 jusqu'au début de l'Holocène (MIS 1-EH). Les étoiles signalent les sites qui sont discutés dans le texte.</caption>

a cultural tradition reflecting the structuration of human group identity in this restricted habitable area (Schild and Wendorf, 2010). The concomitant occurrence of large graveyards at the end of the Late Pleistocene in this area reinforces the hypothesis of strong social units of residential groups (Wendorf and Schild, 2004).

As mentioned earlier, the more numerous and best preserved human remains from this period come from the graveyard of Jebel Sahaba (site 117, MNI = 61; Wendorf, 1968), the Wadi Halfa cemetery (site 6B36, MNI = 36; Hewes et al., 1964) and the Tushka burial ground (site 8905; MNI = 12; Wendorf 1968). All are associated with the Qadan industry. The Qadan sequence is documented in Upper Egypt and Lower Nubia from the end of the Late Pleistocene (~ 18 ka) until the Holocene (Wendorf, 1968; Schild and Wendorf, 2010). In Jebel Sahaba, direct dating of five individuals based on the collagen and mineral fraction of the bones and teeth give a time range of between 18 ka and 11 ka (Wendorf and Schild,

2004; Zazzo, 2014). The oldest Tuskha human remains are dated between ~ 15-11 ka, based on geological and archaeological data, taphonomic observations and several radiocarbon dating results (Albritton and Wendorf, 1968). Although not directly dated, the Wadi Halfa cemetery is considered to be of equivalent age given its archaeological consistency with Jebel Sahaba and Tushka (Greene and Armelagos, 1972). The partial skeleton from Wadi Kubbaniya, also associated with the Qadan artefacts, represents the last and maybe the oldest well-preserved human remains from MIS 2 in the region. Sedimentological and lithic technological evidence could indicate a date as early as 20 ka for this deposit (Wendorf and Schild, 1986). The other human remains from this period (Kom Ombo, Esna and ANE-1) are fragmentary and/or poorly preserved (Reed, 1965; Wendorf, 1968; Lubell, 1974).

Since the first publications related to their find, the individuals from Wadi Halfa and Jebel Sahaba have been described as part of a highly robust population exhibiting a distinctive assemblage of cranial and dental traits compared to recent modern humans (Greene et al., 1967; Anderson, 1968; Greene and Armelagos, 1972). The dental elements are massive and exhibit high frequencies of complex traits that can be related to mass additive features (Greene et al., 1967; Irish, 2005). The cranial remains are also characterised by plesiomorphic features and robust morphologies in relation to powerful masticatory apparatus. Moreover, the level of similarity between the Wadi Halfa and the Jebel Sahaba individuals supports their association with the same Nubian Late Pleistocene population (Anderson, 1968; Greene and Armelagos, 1972). As J.L. Angel and J.O. Kelley (1986) later argued, given its large face and robust mandible, the Wadi Kubbaniya skeleton would fit perfectly in the center of this Nubian Late Pleistocene variation. This robust phenotype is associated with a high average stature (~ 1 m 67) and structural conformation of the lower limb that suggests an active and mobile lifestyle (Shackelford, 2007; Holliday, 2015). In addition, these populations appear to exhibit a higher phenotypic variation than the more recent Holocene populations (Crevecoeur et al., 2009). The figure 6 illustrates the extreme dental size and the range of variation shown by the Nubian Late Pleistocene sample (LPNAE, here composed of Jebel Sahaba, Wadi Halfa and Tuskha) with regard to the lower second molar crown diameters.

These dental dimensions may be related to the complexity of the crown morphology exhibited by Jebel Sahaba and Wadi Halfa, with a high frequency of six-cusped lower first molars and at least five-cusped lower second molars (Greene et al., 1967; Irish, 2000 and 2005). The number of cusps on the lower molars is one of the most suitable non-metric dental trait for identifying population affinities as it preserves the maximum number of neutral genetic signals (Rathmann and Reyes-Centeno, 2020). Interestingly, Nazlet Khater 2 fits in the center of the LPNAE variation, as do several African specimens attributed to the MIS 5 to MIS 3 period, here referred
<figure><img src="image_11.png" /></figure>

**Fig. 6** – Bivariate plot of the lower second molar crown dimensions in centimeters. VL = vestibule-lingual, MD = mesiodistal. NK2 = Nazlet Khater 2, ISH = Ishango, MPH = Middle Pleistocene Hominin, QS = Qafzeh and Skhul, MSA = African specimens attributed to the MIS 5 to MIS 3 period (i.e. Temara, Dar-es-Soltan, Haua Fteah, Klasies River Mouth, Mumba Rock Shelter, Equus Cave and Witkrans), EUP = European Upper Palaeolithic fossils, LPNEA = Late Pleistocene specimens from north-east Africa (i.e Jebel Sahaba and Wadi Halfa), LPNWA = Late Pleistocene specimens from north-west Africa (i.e. Taforalt and Afalou), EHA = Early to mid-Holocene specimens from northeast Africa (Lothagam, Gogoshiis Qabe, Mille Logghia and Lake Besaka 2), RMH = Recent modern human (database, see Kieser, 1990). The ellipses represent 95% of the sample variation.

**Fig. 6** – Diagramme bivarié des dimensions de la couronne de la deuxième molaire inférieure en centimètres. VL = vestibulo-lingual, MD = mésiodistal. NK2 = Nazlet Khater 2, ISH = Ishango, MPH = hominines du Pléistocène moyen, QS = Qafzeh et Skhul, MSA = spécimens africains attribués à la période allant du MIS 5 au MIS 3 (à savoir Temara, Dar-es-Soltan, Haua Fteah, Klasies River Mouth, Mumba Rock Shelter, grotte d'Equus et Witkrans), EUP = fossiles Homo sapiens du Paléolithique supérieur européen, LPNEA = spécimens de la fin du Pléistocène supérieur du nord-est de l'Afrique (à savoir Jebel Sahaba et Wadi Halfa), LPNWA = spécimens de la fin du Pléistocène supérieur du nord-ouest de l'Afrique (à savoir, Taforalt et Afalou), EHA = spécimens du début de l'Holocène d'Afrique du nord-est (à savoir Lothagam, Gogoshiis Qabe, Mille Logghia et lac Besaka 2), RMH = Homo sapiens récents (base de données, voir Kieser, 1990). Les ellipses représentent 95 % de la variation de l'échantillon.

to as the MSA sample (i.e. Dar-es-Soltan, Equus Cave, Haua Fteah, Klasies River Mouth, Mumba X, and Witkrans).

In line with what was observed for Nazlet Khater 2, the combination of plesiomorphic and unique morphometric features in the LPNAE sample, that sit on the fringe, or outside, recent phenotypic diversity, could be the consequence of population isolation and division/fragmentation in Middle Nile Valley at a time of extreme climatic conditions (Kuper and Kröpelin, 2006; Crevecoeur, 2008; Vermeersch and Van Neer, 2015; Pagani and Crevecoeur, 2019). In this context of environmental pressure and geographic constraints, the identification of traces of interpersonal violence on the bones of individuals from different LPNAE sites have attracted a great deal of attention and generated debate about Late Pleistocene warfare (Anderson, 1968, Keeley, 1996; Thorpe, 2003; Wendorf and Schild, 2004; Guilaine and Zammit, 2005; Daković, 2014). The oldest case is documented on the

partial skeleton from Wadi Kubbaniya where two blades were found inside the volume of the body between the rib cage and the lumbar vertebrae. A chip of flint was also found embedded in a partially healed trauma on the left humerus. Finally, this individual also exhibits a healed fracture of the right ulna (Angel and Kelley, 1986; Wendorf and Schild, 1986). Similar observations of embedded lithic and healed fractures have been documented on some individuals buried in the Wadi Halfa cemetery (Hewes et al., 1964; Saxe, 1971; Greene and Armelagos, 1972). However, the most emblematic case is clearly the cemetery of Jebel Sahaba, where anthropological examinations of the skeletons by J. E. Anderson (1968) and B. Butler (1968) revealed the presence of traces of interpersonal violence on the bones of at least half of the Jebel Sahaba individuals. In addition, abundant lithic artefacts were discovered within the body volume or directly embedded in the bones (Wendorf, 1968). On these issues, we can confirm that more than half of
the injured Jebel Sahaba individuals undoubtedly exhibit projectile impact marks (61%), and almost all of them showing signs of trauma (92.7%). We also confirmed that these individuals exhibit clear signs of acts of interpersonal violence involving projectile weapons. The injuries are independent of the age-at-death and sexual diagnosis of the individuals. In addition, the concomitant occurrence of healed and unhealed traumas on the same individuals increases through time, with adolescents, young adults and adults exhibiting this association progressively more frequently (Crevecoeur et al., 2021 and this volume). This observation suggests that acts of interpersonal violence were repeated over time. We suggest that adaptation of the subsistence strategies to territorial and environmental stresses triggered by climatic changes at the end of MIS 2 may be responsible for these sporadic, but recurrent, small-scale conflictual events between semi-sedentary hunter-fisher-gatherer groups.

With the stabilization of more humid conditions during the Early Holocene period (~10.5-7.3 ka), Prehistoric settlements moved to the eastern Sahara that turned into a savannah-like environment, probably more hospitable than the Nile Valley (Nicoll, 2001 and 2004; Kuper and Kröpelin, 2006; Bubenzer and Riemer, 2007; Manning and Timpson, 2014). No precisely dated archaeological sites are documented in the Egyptian Nile Valley during the Early Holocene, but only periodic traces of human presence related to seasonal activities are suspected (Vermeersch, 2001; Kuper and Kröpelin, 2006; Dittrich, 2015). The only two regions that have yielded clear archaeological records of human occupations near the Nile Valley during this Saharan exodus are central Sudan and Nubia (fig. 5). Evidence includes several archaeological sites related to the Khartoum Mesolithic culture that were excavated near the confluence of the White Nile and Blue Nile in central Sudan (Clark, 1989; Haaland, 1993; Usaï et al., 2010; Salvatori, 2012; Suková and Varadzin, 2012; Williams et al., 2015) and sites near Kerma, like Wadi El-Arab and El-Barga, that document human occupation near the Nile Valley between ~10.5-7.3 ka (Honegger, 2006, 2011 and 2012; Honegger and Williams, 2015). The decline in human occupation in the Sahara from 7.3 ka to 5.5 ka relates to the cessation of regular monsoon rains that forced human populations to relocate to new ecological niches and/or to begin the exodus to the Sudanese plains and the Egyptian Nile Valley (Nicoll, 2001 and 2004; Vermeersch, 2001; Kuper and Kröpelin, 2006; Manning and Timpson, 2014).

In parallel with these climatic fluctuations, the beginning of the Holocene witnessed the appearance of new subsistence strategies with the emergence of herding activities. The origin and spread of pastoralism in North Africa is the subject of intense debate about whether it results from one or several independent African domestication centers or is linked to the diffusion and adoption of the practice from other continents (Wendorf and Schild, 1998; Kuper and Riemer, 2013; Stock and Gifford-Gonzales, 2013; Brass, 2018). Circumstantial evidence of early cattle domestication is reported from Nabta Playa

and Bir Kiseiba about ~10-8 ka, which corresponds to the period of stabilization of more humid climatic conditions (Wendorf and Schild, 1980; Gautier, 2001; Jórdeczka et al., 2013). While there is a lack of data on early domestic Holocene bovid remains, large bovids have been documented in association with archaeological contexts from the end of the Late Pleistocene in the Nile Valley, suggesting that bovids had specific significance prior to domestication (e.g. Tuskha, site 8905; Wendorf, 1968; Marshall and Hildebrand, 2002). In addition, the early dates for potential cattle domestication at Nabta Playa and Bir Kiseiba are concomitant with the apparition of the oldest form of pottery in the Sahara and the Nile Valley (Jesse, 2010; Haaland, 2015). Wavy-line and dotted wavy-line potteries are recorded in the earliest phases at Nabta Playa and Bir Kiseiba (Close and Wendorf, 2001; Jesse, 2010). These behavioral changes at the beginning of the Holocene among hunter-gatherer communities might therefore be viewed as a way to accommodate the new climatic conditions of subtle rainfall variations compared to the preceding period of probably more stable, acute aridity by way of more predictable food availability and storage (Marshall and Hildebrand, 2002; Jesse, 2010). The introduction of domestic sheep and goats in Africa is clearly an exogenous contribution, since no wild ancestor is present in Africa (Marshall and Hildebrand, 2002; Lesur-Gebremariam, 2010; Lesur et al., 2014). The oldest occurrence of bones from domestic ovicrapines are documented in the Red Sea mountains (Marinova et al., 2008; Vermeersch et al., 2015) and in the western desert (Gautier, 2001 and 2014) from ~8.2 ka onwards. These dates are consistent with the oldest remains recorded in the south Sinai and are earlier than domestic goat and sheep remains from Northern Egypt, which would suggest their introduction to southern Egypt and north Sudan from southwestern Asia prior to the major diffusion of fully-fledged pastoralism along the Nile Valley around ~7.0 ka, originating from the Levant (e.g. Close, 2002; Marshall and Hildebrand, 2002; Kuper and Kröpelin, 2006; Kuper and Riemer, 2013; Lesur et al., 2014).

While changes in subsistence strategies emerged in the western desert and the Red Sea mountains at the beginning of the Holocene, they do not seem to be related to a fundamental break in the hunter-fisher-gatherer tradition since in many of these contexts, hunting of wild mammals and gathering of wild seeds were still dominant food procurement activities (Kuper and Riemer, 2013; Vermeersch et al., 2015). It was only in the second half of the Holocene (after 7.0 ka), concomitant to the decrease in the monsoonal rains and the resettlement of populations in the Nile Valley refuge zone, that northeast African populations truly developed pastoral ways of life (Kuper and Kröpelin, 2006; Kuper and Riemer, 2013). Evidence of cultural convergence in terms of material uses and funerary practices can be observed in the Neolithic of the Nile Valley from the same period (i.e. during the 5th millennium BCE; Wengrow et al., 2014). This timescale (~7.3-5.7 ka) also corresponds to the expansion period of the Y-chromosome haplogroup R-V88 into
the Sahelian/Savannah pastoralist gene pool that seems
to be associated with an Asia-to-Africa back migration
(Cruciani et al., 2010; Kulichová et al., 2017).

Given this climatic, behavioral and cultural frame-
work of change at the beginning of the Holocene in the
Nile Valley, the cranio-facial phenotypic differences doc-
umented between Nubian Late Pleistocene individuals
(Jebel Sahaba, Wadi Halfa) and mid-Holocene to recent
populations in this region have been widely discussed.
For some authors, the differences in cranial and dental
morphology are linked to a gradual adaptation to changes
in subsistence activities (Greene et al., 1967; Carlson and
Van Gerven, 1977; Galland et al., 2016). This morpho-
functional hypothesis postulates population continuity
in the Nile Valley during the Holocene and attributes the
strong morphological differences to changes in diet, car-
ies-related selection and gracilization processes (Carlson
and Van Gerven, 1977). For others, these differences,
notably in non-metric dental trait variations, are genet-
ically related and suggest some level of population dis-
continuity at the beginning of the Holocene (Groves and
Thornes, 1999; Irish, 2000 and 2005; Holliday, 2015).
However, the absence of Early Holocene samples in these
studies that would allow the hypotheses of continuity or
replacement of populations in the Nile Valley to be tested
limits the discussion.

The Early Holocene site of El-Barga, situated in Nubia more than 10 km east of the city of Kerma, offers a unique opportunity to address these questions of Early Holocene population processes in the Nile Valley (fig. 5). Excavated since 2001 by the Swiss archaeological mission in Sudan (Honegger, 2006), the site has preserved two archaeological assemblages, a Mesolithic settlement with habitat structures and burials, and an Early Neolithic cemetery. The two occupations are located in the same area and dated by radiocarbon isotopic analyses on shells and ostrich eggshells directly associated with the burials (Honegger and Williams, 2015). The Mesolithic assemblage, situated at the top of the hill, has been dated to ~ 10.2-9.1 ka, and the Early Neolithic cemetery is dated to 8.1-7.5 ka, which corresponds to the earliest Neolithic occupation in Nubia (Salvatori and Usaï, 2008). Preliminary analyses of funerary practices, associated artefacts, as well as morphometric comparisons of the human remains, suggest substantial biological and cultural differences between the two human occupations, separated by about a millennium (Honegger, 2006 and 2011; Crevecoeur, 2012b).

Morphometrically, the El-Barga Mesolithic skeletons (EBK_M) can be described as extremely robust. They exhibit strong muscular attachments on the cranium and the infra-cranium skeleton. Regarding dental dimensions and morphology, the Mesolithic sample possesses higher dental diameters on average than the Early Neolithic group (EBK_N). In addition, there is a statistically significant difference in terms of shape of the lower second molars (LM2) and the lower second premolars (LP2). The latter observation is related to the fact that Mesolithic individuals exhibit a higher frequency of lower

second molars with fifth cusps compared to the Neolithic
group, while differences in the shape of the LP2s depend
on the proportionally wider bucco-lingual diameters of
the Epipalaeolithic individuals (Benoiston et al., 2018).
Comparative morphometric analyses of dental remains
show strong biological affinities between the Mesolithic
sample from El-Barga and the Nubian Late Pleistocene
population from Jebel Sahaba. These characteristics sig-
nificantly differentiate the Mesolithic and Early Neolithic
samples at El-Barga (Benoiston et al., 2018). In-depth
investigations of the dental tissue proportions between
both El-Barga samples have highlighted variations in size
and conformation of these inner structures that support
the hypothesis of a biological differentiation between the
two El-Barga populations. For instance, the results from
the permanent upper central incisors (UI1s) show that
the Mesolithic sample exhibits higher values of crown,
enamel and dentine volumes than the Neolithic sample,
as illustrated in figure 7. The latter figure also maps the
repartition of the enamel in both samples. The Mesolithic
UI1s possess a significantly higher enamel thickness on
average than the Early Neolithic group, notably on the
buccal surface of the tooth. This result indicates a dif-
ference in conformation of the dental tissue that is inde-
pendent of the size of the tooth (Benoiston et al., 2018).
Although the development of the permanent incisor is
more plastic than the posterior teeth (Braga and Heuzé,
2007), the dominance of genetic factors compared to
environmental ones in the dental crown development is
underscored (e.g. Townsend and Brown, 1978; Dempsey
and Townsend, 2001; Hlusko et al., 2004; Townsend
et al., 2009). Thus, it is unlikely that the differences in
dental tissue proportion would only be related to dietary
changes in the El-Barga case in such a short timescale and
at the onset of pastoralism. On the contrary, we believe
that these results indicate major biological differences
between both groups, suggesting possible biological dis-
continuity between the Mesolithic and the Neolithic pop-
ulations from El-Barga.

This hypothesis is supported by the results of crani-
ometric comparisons. The Mesolithic individuals from
El-Barga exhibit long and wide mandibles, characterized
by high mandibular corpus and wide ramus, while the
Neolithic mandibles differ significantly with regard to
these dimensions. Their mandibles are shorter, narrower
and characterized by a consistently low height of the
mandibular corpus. Differences in craniofacial morphol-
ogy are also striking, as illustrated in figure 8 and by the
results of a PCA analysis on seven size-adjusted variables
(fig. 8). In the projection of the first and third principal
components in figure 8, the El-Barga individuals clus-
ter in very different areas of the plot in relation to their
chronological affinities. The El-Barga Mesolithic group
cluster with Late Pleistocene specimens from north-east
Africa (LPNAE; i.e. Jebel Sahaba, Wadi Halfa) along the
positive value of the PC1 that correlates with the relative
length and breadth of the face compared to the neurocra-
nial conformation. On the other hand, the El-Barga Neo-
lithic individuals are clearly dissociated from this positive
<figure><img src="image_12.png" /><figcaption>**Fig. 7** – Right: Cartographic representation of the enamel thickness variation for the El-Barga Mesolithic and Neolithic UI1s. The teeth are represented in occlusal (O), medial (M), distale (D), vestibular (V) and lingual (L) views. Left: Boxplot of the mean and range of variation of the relative enamel thickness (RET 3D) of the UI1s for the Mesolithic and Neolithic samples of El-Barga (following Benoiston et al., 2018).</figcaption></figure>

<caption>**Fig. 7** – À droite : représentation cartographique de la variation de l'épaisseur de l'émail pour les UI1 mésolithiques et néolithiques d'El-Barga. Les dents sont représentées en vues occlusale (O), médiale (M), distale (D), vestibulaire (V) et linguale (L).</caption>

<figure><img src="image_13.png" /><figcaption>**Fig. 8** – Bivariate plot of the projection of the first and third principal component of the PCA on size-adjusted cranial dimensions. Bottom left: Correlation circle showing the position of the variables in relation to the two plotted PCs. FMB, bifrontal breadth; XML, malar length; FRC, frontal chord; PAC, parietal chord; OCC, occipital chord; XCB, maximum cranial breadth; GOL, maximum cranial length. NK2 = Nazlet Khater 2, QS = Qafzeh and Skhul, JS = Jebel Sahaba, WH = Wadi Halfa, TAF = Taforalt, LPSwa = Late Pleistocene from south-west Asia (i.e. Natufian; see Bocquentin, 2003), EBK_M = Mesolithic from El-Barga, EBK_N = Neolithic from El-Barga, KDK = Kadruka 1 sample, RMH = Recent modern human (here Egyptian population; see Howells, 1996). The pink ellipse represents 95% of the RMH variation (Howells, 1996). The dotted lines delimit convex hulls of selected samples. Photograph inserted in the top right part of the graph illustrates the cranium of EBK_M_123 and EBK_N_79 individuals in lateral view.</figcaption></figure>

<caption>**Fig. 8** – Diagramme bivarié de la projection de la première et de la troisième composante principale de l'ACP sur les dimensions crâniennes normées. En bas à gauche : cercle de corrélation montrant la position des variables par rapport aux deux composantes principales projetées. FMB, largeur bifrontale ; XML, longueur malaire ; FRC, corde frontale ; PAC, corde pariétale ; OCC, corde occipitale ; XCB, largeur crânienne maximale ; GOL, longueur crânienne maximale. NK2 = Nazlet Khater 2, QS = Qafzeh et Skhul, JS = Jebel Sahaba, WH = Wadi Halfa, TAF = Taforalt, LPSwa = spécimens de la fin du Pléistocène supérieur d'Asie du sud-ouest (à savoir les Natoufiens ; voir Bocquentin, 2003), EBK_M = individus mésolithiques d'El-Barga, EBK_N = individus néolithiques d'El-Barga, KDK = individus néolithiques de Kadruka 1, RMH = Homo sapiens récents (ici population égyptienne ; voir Howells, 1996). L'ellipse rose représente 95 % de la variation du groupe RMH. Les lignes pointillées délimitent les polygones convexes contenant les individus des échantillons sélectionnés. La photographie insérée dans la partie supérieure droite du graphique illustre les crânes des individus EBK_M_123 et EBK_N_79 en vue latérale.</caption>
PC1 grouping. Their position in the upper left quadrant is influenced by their proportionally longer occipital chord. It is worth noting that the Late Pleistocene individuals from southwest Asia (LPSwa), as well as the individuals from the later Nubian Neolithic site of Kadruka 1 (KDK) are included, with most of the EBK_N specimens in the Egyptian recent human variation used here as a reference.

All the anthropological evidence points to significant craniofacial and dental differentiation in terms of size and conformation between both El-Barga samples. Following D. S. Carlson and D. P. Van Gerven (1977), and more recently, M. Galland et al. (2016), the strong phenotypic differences observed on more chronologically separated samples (namely, the LPNAE sample in comparison to the Mid-Holocene (< 5.5 ka) Nile Valley populations) are related to changes in masticatory function and diet. Analysis of the only anthropological sample from the beginning of the Holocene in the Nubian part of the Nile Valley calls this hypothesis into question. El-Barga fills a chronological gap in the Early Holocene record and the comparative analyses of the human remains from both occupations underline strong phenotypic differences between them. These changes are documented on a short timescale (one millennium) and during a period of limited climatic and environmental change. In addition, while incipient pastoralism can be identified during the EBK-N period, both El-Barga populations still seem to have relied mainly on Nilotic resources (Linseele, 2012), leaving little evidence of a radical change in lifestyle or diet between the Mesolithic and the Neolithic groups. It is only by the end of the 6th millennium that evidence establishes the development of fully-fledged pastoralism in Nubia (Kuper and Kröpelin, 2006). Therefore, we consider that our results support the hypotheses of biological discontinuity between the two El-Barga groups. Without excluding the possibility of a certain level of continuity, the anthropological study of the El-Barga assemblage suggests a complex history of population processes in the Nile Valley during this crucial, but poorly documented period of the beginning of the Holocene.

### 3. THE HORN OF AFRICA AT THE END OF THE PLEISTOCENE AND THE BEGINNING OF THE HOLOCENE

Ideally located between Africa and Eurasia, the Horn of Africa has the potential to play a crucial role as a migratory corridor out of and back to Africa. However, the level of resolution offered by the Nile Valley to discuss population processes and phenotypic diversity at the end of the Late Pleistocene and the beginning of the Holocene is currently unavailable in the Horn of Africa. While the region is well-known for its Plio-Pleistocene hominin record and the discovery of the early representative of *Homo sapiens* (e.g. Asfaw et al., 1999 and 2002; White et al., 2003; Alemseged et al., 2006), research into the Late Pleistocene and Early Holocene periods is less

frequent. The earliest major contribution to our understanding of the MSA and LSA archaeological sequences in this area was proposed by J. D. Clark (1954), and although research increased from the 1970s onward, relatively few well-dated Late Pleistocene human occupations have been identified compared to other African regions (Brandt, 1986; Assefa, 2006; Ménard et al., 2014; Pleurdeau et al., 2014; Brandt et al., 2017; Leplongeon et al., 2017; Tribolo et al., 2017). If we focus on the number of sites preserving Late Pleistocene and Early Holocene human remains, the dearth of paleoanthropological data is striking (fig. 9).

For the beginning of the Late Pleistocene, the number of sites with securely dated archaeological sequences is

<figure><img src="image_14.png" /><figcaption>**Fig. 9** – Map of the Horn of Africa with the location of sites preserving human remains dated from the MIS 3 to the end of the early Holocene period (MIS 1-EH). Star identifies the Hara Idé 3 site discussed in the text.</figcaption></figure>

<caption>**Fig. 9** – Carte de la Corne de l'Afrique avec la localisation des sites ayant livré des restes humains datés depuis le MIS 3 jusqu'au début de l'Holocène (MIS 1-EH). L'étoile indique le site Hara Idé 3 évoqué dans le texte.</caption>

very low and the quasi absence of sites dating to MIS 4 also raises questions about the possible absence of human presence in vast areas of the Horn of Africa (Brandt et al., 2017). During MIS 3, archaeological sequences provide evidence of continued occupation by hunter-gatherer groups (Assefa, 2006). Among these sites, only two in the Dire Dawa region have yielded human remains: Porc-Épic and Goda Buticha (fig. 10; Vallois, 1951; Pleurdeau, 2003; Pleurdeau et al., 2014).

In Porc-Épic, a poorly preserved mandibular corpus fragment was found in 1933 during H. Breuil, P. Teilhard de Chardin and P. Wernert's excavations (fig. 10a; Clark and Williamson, 1984). H.-V. Vallois (1951) noted the absence of mental protuberance, the presence of archaic features on the symphysis, and the size and robustness of the corpus which led him to propose an association with archaic populations. The stratigraphic position of the mandibular fragment is unknown, but a high-resolution low-background gamma-ray spectrometry applied
<figure><img src="image_15.png" /><figcaption>**Fig. 10** – Composite image of MIS 3 human remains from Porc-Épic (a to d) and Goda Buticha (e): a, mandibular corpus described by H.-V. Vallois (1951); b, left parietal fragment; c, left occipital fragment; d, first upper left premolar; e, cranial vault fragments.

**Fig. 10** – Image composite des restes humains MIS 3 de Porc-Épic (a à d) et de Goda Buticha (e) : a, corps mandibulaire décrit par H.-V. Vallois (1951) ; b, fragment de parietal gauche ; c, fragment d'occipital gauche ; d, première prémolaire supérieure gauche ; e, fragments de voûte crânienne.</figcaption></figure>

directly to the mandible yielded a date of 50 ka that is
consistent with the chronological time range of the sedi-
mentary accumulation dated by obsidian hydration and
radiocarbon between ~ 77-40 ka (Michels and Marean,
1984; Assefa, 2006; Leplongeon, 2014). Three addi-
tional unpublished human remains from Porc-Épic, two
cranial fragments and a first upper left premolar (UP1)
were discovered during the 1998 fieldwork conducted by
Z. Assefa and D. Pleurdeau to obtain new data on Porc-
Épic's stratigraphic sequence (fig. 10b, 10c and 10d;
Pleurdeau, 2003 and 2004). They are associated with
Unit III, dated by radiocarbon around 40 ka (Pleurdeau,
2005; Assefa, 2006; Leplongeon, 2014). The last human
remain, a cranial vault fragment, dated from MIS 3,
comes from the nearby cave of Goda Buticha (fig. 10e).
It is associated with Level IID whose *terminus ante quem*
of 36.6-33 ka is given by two radiocarbon dates on char-
coal (Assefa et al., 2014; Pleurdeau et al., 2014). Given
the state of preservation and the fragmentary nature of
these MIS 3 human remains, it seems impossible to char-

acterize the phenotypic diversity of human populations
in this area in the Late Pleistocene. While the mandibular
corpus of the Porc-Épic mandible is indeed robust, with
corpus dimensions on the edge of recent human variation
(fig. 11), the first upper premolar crown does not exhibit
any complexity and its diameters are included in the Late
Pleistocene and Early Holocene African variation.

The figure 11 also illustrates the position of the man-
dibular remains from the other Late Pleistocene and early
Holocene Horn of Africa specimens (LPHA and HHA
samples). All of them cluster close to Porc-Épic and
Nazlet Khater 2, exhibiting robust mandibular corpus
dimensions.

Human remains associated with MIS 2 in the Horn
of Africa are as scarce as those from MIS 3, although
more complete (fig. 9). One reason is probably tied to
the stratigraphic hiatus documented in several sites in
this region between ~ 30-11 ka (Assefa, 2006; Pleaur-
deau et al., 2014; Brandt et al., 2017; Tribolo et al., 2017;
Jones, 2020; Khalidi et al., 2020). In Somalia, the sites
<figure><img src="image_16.png" /></figure>

**Fig. 11** – Bivariate plot of the mandibular corpus dimensions between the first and second lower molars in centimeters [M69b = corpus thickness; M69(2) = corpus height; see Braüer, 1988]. PE = Porc-Épic, NK2 = Nazlet Khater 2, QS = Qafzeh and Skhul, MSA = African specimens attributed to the MIS 5 to MIS 3 period (i.e. Border Cave, Temara, Dar-es-Soltan, Klasies River Mouth, Loiyangalani and Mumba Rock Shelter), ISH = Ishango, LPNA = compilation of LPNAE and LPNAW samples (i.e. Jebel Sahaba, Wadi Halfa, Wadi Kubbaniya and Taforalt), LPHA = Late Pleistocene specimens from the Horn of Africa (i.e. Guli Waabayo, GW-BU1, and Hara Idé 3, HI3-Q28), HHA = Early and Mid-Holocene samples from the Horn of Africa (i.e. Lake Besaka 2, Gogoshiis Qabe and Mille-Logghia), EHA = Early to Mid-Holocene specimens from east Africa (Lothagam), RMH = Recent *Homo sapiens* (see Ribot, 2011). The ellipse represents 95% of the variation.

**Fig. 11** – Diagramme bivarié des dimensions du corps mandibulaire entre la première et la deuxième molaire inférieure en centimètres [M69b = épaisseur du corps ; M69(2) = hauteur du corps ; voir Braüer, 1988]. PE = Porc-Épic, NK2 = Nazlet Khater 2, QS = Qafzeh et Skhul, MSA = spécimens africains attribués à la période allant du MIS 5 au MIS 3 (à savoir Border Cave, Temara, Dar-es-Soltan, Klasies River Mouth, Loiyangalani et Mumba Rock Shelter), ISH = Ishango, LPNA = compilation d'échantillons LPNAE et LPNAW (à savoir Jebel Sahaba, Wadi Halfa, Wadi Kubbaniya et Taforalt), LPHA = spécimens de la fin du Pléistocène supérieur de la Corne de l'Afrique (à savoir Guli Waabayo, GW-BU1, et Hara Idé 3, HI3-Q28), HHA = spécimens de la première moitié de l'Holocène de la Corne de l'Afrique (à savoir lac Besaka 2, Gogoshiis Qabe et Mille-Logghia), EHA = spécimens du début de l'Holocène d'Afrique du nord-est (à savoir Lothagam), RMH = *Homo sapiens* récents (ici base de données africaine Ribot, 2011). L'ellipse représente 95% de la variation.

from Rifle Range and Guli Waabayo preserved sedimentary records covering the Last Glacial Maximum (Jones et al., 2018; Jones, 2020). The latter also delivered the oldest human remains from MIS 2. Direct dating on bone apatite of the remains from Guli Waabayo Burial 1 (GW-BU1) was achieved during the ANR Big Dry program (18683 ± 82 BP, UBA-34897 Muse17239). The result is consistent with chronological reassessment of the Guli Waabayo rock shelter, indicating human activity between ~26-6 ka (Brandt, 1986; Jones, 2020). The ANR program also provided a chronological background to a deciduous upper central incisor identified in the faunal collection from the Lake Besaka 4 locality (fig. 9) with the dating of an associated ostrich eggshell to 11699 ± 47 BP (UBA-34907 Muse17252; Clark and Williams, 1978; Brandt, 1982).

The limited record of human occupation in the Horn of Africa during the Last Glacial Maximum may be related to partial abandonment of the area during this period of extreme aridity (Tierney and DeMenocal, 2013). Analyses of lacustrine sediments, isotopic proxy for hydroclimate and pollen sequences have provided a clear image of the impact of large-scale climate changes in the Horn of Africa. The results consistently highlight dramatic hydroclimate changes from MIS 3 until the end of the African Humid Period (e.g. Gasse, 1977 and 2000; Lamb et al., 2002; Marshall et al., 2009; Tierney and DeMenocal, 2013; Foerster et al., 2015; Fersi et al., 2016). Arid conditions prevailed during MIS 3 until the Last Glacial Maximum, followed by a severe dry period associated with the Heinrich Event 1 in the North Atlantic. The abrupt transition to more humid conditions was
interrupted by a return to a dryer environment during the Younger Dryas. The strong climatic variations and hydrological instability, notably documented by the fluctuation in lake levels, unquestionably challenged the adaptation capacities of human groups in this area (Gasse, 1977 and 2000; Marshall et al., 2011; Khalidi et al., 2020).

Two exceptions are currently known from the Horn of Africa, that suggest the region experienced heterogeneous human responses to the environmental changes caused by the cooling and drying of MIS 2. G. Ossendorf et al. (2019) documented MSA occupations of the Fincha Habera rock shelter in the Bale mountains (~4,000 m above sea level) between 47-31 ka with intensive hunting of giant mole rats. E.A. Hensel et al. (2021) reported an occupation throughout the LGM of Sidocho rock shelter (1,930 m above sea level) in the southwestern Ethiopian highlands. The MIS 2 lithic assemblage from Sidocho rock shelter is dominated by microblades lacking retouch and made from obsidian (Hensel et al., 2021). Thus, the lithic industry differs substantially from that at PorcÉpic and Goda Buticha, in which microliths are present, but the assemblages are dominated by larger, retouched tools and small, narrow unifacially or bi-facially flaked points made predominately on chert (Pleurdeau, 2004 and 2005; Leplongeon, 2014; Leplongeon et al., 2017; Pleurdeau et al., 2014). The other exception lies in Somalia. The continuous occupations documented in Somalia appear to correlate with more stable climate conditions in this specific area (Reid et al., 2019). Arguments in favor of the possible absence of human occupation, or the splitting up and maybe isolation of human groups in the Horn of Africa at the end of the Late Pleistocene and the beginning of the Holocene, are found in late occurrence pottery, herding (< 4 ka) and agricultural activities (< 3 ka) compared to adjacent African regions (Cauliez et al., 2008; Lesur et al., 2014; Gutherz et al., 2015; Khalidi et al., 2020). In addition, reduced mobility and specialized hunting strategies are documented in sites preserving archaeological records from this period, such as Guli Waabayo (Jones et al., 2018; Jones, 2020). Finally, the hypotheses of possible long-term isolation and adaptation of populations from this region are also supported by genetic studies (Luis et al., 2004; Rowold et al., 2007; Gallego Llorente et al., 2015).

Within this context, the discovery of a new site in the Republic of Djibouti in 2003, Hara Idé 3 (HI3), tentatively associated with the end of the Late Pleistocene and the beginning of the Holocene, with well preserved human remains, was fortuitous (fig. 9). Hara Idé 3 is located on the southern shore of the Dagadlé oued in the Gobaad basin, 30 km southeast of lake Abhe. The Gobaad basin is a large complex of basaltic grabens that document the fluctuation of lake Abhe during the Pleistocene (Gasse, 1977; Vellutini and Piguet, 1994). This depression has been extensively surveyed for Prehistoric occupation since the 1980s and the discovery of Oldowan assemblages (Chavaillon et al., 1987). Later archaeological programs succeeded one another, focused on identifying occupation sites in relation to first food production

societies in the region (Gutherz and Joussaume, 2000; Gutherz, 2008; Gutherz et al., 2015, Cauliez et al., 2018; Cauliez, 2019). From MIS 4 to the Holocene, the Gobaad basin was repeatedly, and to various extents, filled by the transgressions of Abbe lake in relation to paleoclimatic fluctuations (Gasse, 1977 and 2000). Changes in the lake-shore levels affected human occupation in this region and are responsible for the burying and/or erosion of archaeological evidence preceding the last great transgression (~ 10 ka; fig. 12; Gasse, 2000; Gutherz et al., 2015; Coudert et al., 2018). This is why the discovery of hundreds of human bones and tooth fragments embedded in a lacustrine limestone matrix at Hara Idé 3, together with various faunal remains and lithic artifacts that were initially associated with Late Pleistocene and Early Holocene deposits, was so exceptional. These remains were collected between 2003 and 2005 during rescue excavations directed by H. Duday in the framework of the franco-djiboutian archaeological mission. Given the potential importance of the site, additional archaeological campaigns were organized between 2016 and 2019 in order to clarify the geological and chronological context of these remains.

The geological data from the new excavation campaigns and the dating results allowed the chronostratigraphic context of the Hara Idé 3 archaeological site to be secured. Given the scarcity of human remains in the Horn of Africa for the end of the Late Pleistocene, the discovery of new human remains dated to the Late Upper Pleistocene (~18-13.5 ka) in this poorly documented part of the world is crucial to the discussion about the adaptation and/or isolation of human populations in Africa during these times of intense climatic variation (Crevecoeur et al., 2019). Preliminary morphometric investigations of the most complete mandible from the site and found in the pit structure (HI3-Q28; fig. 13) highlighted the robustness of the corpus and the mandibular ramus (Matu et al., 2017). In multivariate comparative analyses, the Hara Idé 3 mandible shows affinities with earlier specimens from the Late Pleistocene, characterized by a relatively long and thick mandibular corpus and a short wide ramus. This conformation explains its position on the upper left quadrant of the graph in figure 13. HI3-Q28 mandible lies at the edge of extant human variation and, given these proportions, can be differentiated from Holocene individuals from the Horn of Africa (HHA) as well as from Nile Valley Late Pleistocene specimens (fig. 13).

These results show that HI3 shares some features with NK2 or Ishango, but seems to differ from the variation in the Late Pleistocene sample from the Nile Valley (LPNAE). Its mandible possesses morphometric characteristics that distinguish it from extant populations. The HHA specimens (here represented by Gogoshiis Qabe, Mille-Logghia and Lake Besaka 2) exhibit great variability, two of them being at the edge of extant human variation, but none of them plots close to Hara Idé 3. This variation in conformation is mirrored by great variation in size. While the latter specimens have a thick and wide mandible associated with large teeth (fig. 13), other
ers, like individuals from Goda Buticha, are characterized by medium to small post-cranial and dental remains (Pleurdeau et al., 2014). These observations of large variations in size and shape between the different sites, although based on limited data from the Holocene period in the Horn of Africa, call into question the relationship between Late Pleistocene specimens like Hara Idé 3 and the Holocene populations in this region, as well as their level of isolation.

## 4. CONCLUSIONS

In this review of the paleoanthropological data available in northeast Africa during the second half of the Late Pleistocene and the beginning of the Holocene, we sought to highlight general trends regarding past modern human phenotypic variation, leading to a discussion of population diversity, adaptation and affinities during this period of major climatic and cultural changes.

In the Nile Valley, anthropological data indicate the persistence of robust phenotypes associated with plesi-

<figure><img src="image_17.png" /></figure>

**Fig. 12** – Top: Lake Abhe fluctuation level (blue line; see Gasse, 1975) during the Holocene and altitudinal position of Hara Idé 3 and Mid-Holocene archaeological sites investigated by the PSPCA project (Cauliez, 2019). Bottom: Localisation of the sites in the Gobaad basin (following Bruxelles and Mologni, 2019). m a.s.l.: meters above sea level.

**Fig. 12** – En haut : niveau de fluctuation du lac Abhé au cours de l'Holocène (ligne bleue ; voir Gasse, 1975) et position altitudinale du site archéologique d'Hara Idé 3 et des sites datant du milieu de l'Holocène fouillés dans le cadre du projet PSPCA (Cauliez, 2019). En bas : localisation des sites dans le bassin de Gobaad (d'après Bruxelles et Mologni, 2019). m a.s.l. : mètres au-dessus du niveau de la mer.
<figure><img src="image_18.png" /><figcaption>**Fig. 13** – Bivariate plot of the first and second principal component of the PCA on size-adjusted mandibular dimensions. HI3 = Hara Idé 3 (HI3-Q28), QS = Qafzeh and Skhul, LPSEA = Late Pleistocene specimens from east and south Africa (i.e. Olduvai Hominid 1 and Springbok Flats), NK2 = Nazlet Khater 2, ISH = Ishango, LPNEA = Late Pleistocene specimens from north-east Africa (i.e. Jebel Sahaba and Wadi Halfa), LPNWA = Late Pleistocene specimens from north-west Africa (i.e. Taforalt and Afalou), HHA = Early and Mid-Holocene samples from the Horn of Africa (Lake Besaka 2, Gogoshiis Qabe and Mille-Logghia), EHA = Early to Mid-Holocene specimens from east and south Africa (Lothagam, Gamble Cave and Fish Hoek Cave), RMH = Recent *Homo sapiens* (see Ribot, 2011). Photograph inserted in the top left part of the graph illustrates the mandible HI3-Q28 in superior view.</figcaption></figure>

<caption>**Fig. 13** – Diagramme bivarié de la première et de la deuxième composante principale de l'ACP sur les dimensions mandibulaires normées. HI3 = Hara Idé 3 (HI3-Q28), QS = Qafzeh et Skhul, LPSEA = spécimens du Pléistocène supérieur d'Afrique de l'Est et du Sud (Olduvai Hominid 1 et Springbok Flats), NK2 = Nazlet Khater 2, ISH = Ishango, LPNEA = spécimens de la fin du Pléistocène supérieur du nord-est de l'Afrique (à savoir Jebel Sahaba et Wadi Halfa), LPNWA = spécimens de la fin du Pléistocène supérieur du nord-ouest de l'Afrique (à savoir, Taforalt et Afalou), HHA = spécimens de la première moitié de l'Holocène de la Corne de l'Afrique (à savoir lac Besaka 2, Gogoshiis Qabe et Mille-Logghia), EHA = spécimens de la première moitié de l'Holocène d'Afrique de l'Est et du Sud (à savoir Lothagam, Gamble Cave, Fish Hoek Cave), RMH = *Homo sapiens* récents (voir Ribot, 2011). La photographie insérée dans la partie supérieure gauche du graphique illustre la mandibule HI3-Q28, en vue supérieure.</caption>

omorphic features related to size and shape from MIS 3 until the end of the Late Pleistocene. These characteristics that lie at the edge of recent modern human diversity are also present in the only Early Holocene sample from the Nile Valley. Although based on a very limited number of fossils, the data support hypotheses of population isolation and biological continuity of human groups in the Nile Valley from the end of the Late Pleistocene until the beginning of the Holocene. After ~ 8 ka, human remains from Nubia, notably, show a more gracile cranio-dental phenotype, whose origin could be related to the arrival of new populations in the area concomitant with the spread of pastoralism.

While changes in climate conditions also influenced human settlements in the Horn of Africa, dynamic popu-

lation issues are more difficult to address with the limited fossil records available. Scattered morphological information from a few Late Pleistocene fossils from Ethiopia, Somalia and the Republic of Djibouti seem to indicate overall robust phenotypes, while Holocene specimens express greater diversity in terms of shape and size dimorphism. Cultural changes in the Horn of Africa in relation to herding and agriculture appear quite late compared to the Nile Valley region. In addition, although ideally situated between Africa and Asia, the role of the Horn of Africa as a migratory corridor during the Late Pleistocene and the beginning of the Holocene is currently little supported by genetic or cultural data. Rather, scenarios involving population isolation and the development of specific adaptation are favored.
The combination of plesiomorphic and unique mor-
phometric features seen in Late Pleistocene African spec-
imens in the Nile Valley and the Horn of Africa from
MIS 3 to the Holocene could be the consequence of pop-
ulation isolation and division/fragmentation, whose origin
could be at least partially related to climate variations. In
this regard, paleoanthropological data are consistent with
a genetically-driven model of modern human origin and
diversification that support hypotheses of African mul-
ti-regionalism and deep population substructures. The
paleoanthropological data from the Nile Valley and the
Horn of Africa have potential implications concerning the
debate about plausible population dynamics that could
have led to the out-of-Africa expansion. The genomes
of non-Africans harbor the signature of a bottleneck, or
a reduction in overall diversity, which can be dated to
around 70 ka (Malaspinas et al., 2016). Putting together
genetic evidence for a Northern exit OoA (Pagani et al.,
2015), archaeological and palaeoclimatic evidence for a
drastic reduction in human presence along the lower Nile
Valley from MSI 4 (70-60 ka) until ~ 25 ka (Vermeersch
et al., 1990; Van Peer, 2004; Vermeersch and Van Neer,
2015), as well as the paleoanthropological data presented
here suggesting isolation and fragmentation of Late Pleist-
cocene human populations in the Nile Valley, we may
postulate that the progressive drying out of the North-East
African region from 70 ka triggered a population bot-
tleneck (Pagani and Crevecoeur, 2019). The majority of
these fragmented human groups may eventually have died
out or merged back with the broader sub-Saharan popula-
tion. A small subset of them may instead have reached the
Mediterranean shores and subsequently expanded west,
along the North African coast, and east towards Eurasia.
Such a scenario would imply that the potential cause of
the genetic bottleneck that characterizes all non-African
groups was the gradual increase in aridity of the Nile
corridor rather than the out-of-Africa expansion of a few
wanderers during environmentally permissive conditions.
It also suggests that this bottleneck did not take place at

the gateways of Africa, but rather, within Africa (along the
Nile basin). This highly speculative scenario should now
be confronted to comparative analyses of Late Pleistocene
specimens from Eurasia to outline possible affinities and
illustrate how the analysis of African human remains from
MIS 3 onwards is crucial to further understanding the evo-
lutionary history of our species.

**Acknowledgments:** This study was supported by the French Agence Nationale de la Recherche (ANR-14-CE31 BIG DRY) and by the LabEx LaScArBx (LASCARBX-AAP5-2015). We thank A. Zazzo (MNHN) and M. Gosselin (MNHN) who dated Guli Waabayo and Lake Besaka during the ANR project and allowed us to present the results in this paper. We are grateful to H. Duday (CNRS) that entrusted us with the reassessment of the Hara Idé 3 archaeological site and allowed us to study the Neolithic collections from Djibouti Republic that he excavated. M. Honegger (University of Neuchâtel) has granted us access to the El-Barga collection. We thank D. Antoine (British Museum) for the access to the Jebel Sahaba collection. We are grateful to F. Bocquentin (CNRS) for sharing her metric database of Natufian individuals. We thank H. Temming (Max-Planck Institute, Leipzig) for providing the µCT scan data of the Hofmeyr cranium, and F. Grine for the opportunity to study it. We are grateful to R. Levedin (Université de Bordeaux), for the µCT acquisitions of the material from Djibouti and the GQ-BU16 cranium from Somalia, and to S. Brandt (University of Florida) for entrusting the Guli Waabayo and Gogoshiis Qabe specimens for examination. We also thank P. Semal, J. Brecko and A. Mathys (Royal Belgian Institute of Natural Sciences-RBINS), for entrusting the LAK specimens from Shum Laka, Cameroon, for examination and for µCT acquisitions in Brussels. Finally, we are grateful to Z. Assefa (Ethiopian Education and Research Network) who granted us access to the Goda Buticha human remains, to Z. Alemseged (University of Chicago) for the autorisation to examine the Mille-Logghia collection, and to the ARCCH for allowing us to study the human remains from lake Besaka in the National Museum of Ethiopia.

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### Isabelle CREVECOEUR

UMR 5199-PACEA, CNRS, université de Bordeaux, Pessac, France
isabelle.Crevecoeur@u-bordeaux.fr

### Marie MATU

UMR 5199-PACEA, CNRS, université de Bordeaux, Pessac, France

### Marie-Hélène DIAS-MEIRINHO

UMR 5608-TRACES, université de Toulouse Jean-Jaurès, Toulouse, France

### Priscilla BAYLE

UMR 5199-PACEA, CNRS, université de Bordeaux, Pessac, France

### Osbjorn PEARSON

Department of Anthropology, The University of New Mexico, Albuquerque, New Mexico, USA
Du Big Dry à l'Holocène en Afrique de l'Est et au-delà
From the Big Dry to the Holocene in Eastern Africa and beyond
Actes de la séance de la Société préhistorique française de Toulouse (septembre 2019)
Textes publiés sous la direction de Joséphine Lesur, Jessie Cauliez, Lamya Khalidi, Laurent Bruxelles, Isabelle Crevecoeur, David Pleurdeau, Chantal Tribolo et François Bon Paris, Société préhistorique française, 2023
(Séances de la Société préhistorique française, 20), p. 39-74
www.prehistoire.org
ISSN : 2263-3847 – ISBN : 2-913745-93-8

# A Comparative Look at Technical Traditions in the Horn of Africa and the Nile Valley at the End of the Pleistocene

## *Regards croisés sur les traditions techniques dans la Corne de l'Afrique et dans la vallée du Nil à la fin du Pléistocène*

Alice LEPLONGEON, Katja DOUZE, Behailu HABTE, Lamya KHALIDI, Clément MÉNARD, David PLEURDEAU, François BON

**Abstract:** Today, the Horn of Africa and north-eastern Africa are connected geographically by the Nile and its tributaries, several of which originate in the Horn. This connectivity evolved over the course of the Pleistocene and despite its potentially central role in the dispersal of humans within and out of Africa, the interactions between human groups of the two regions remain poorly understood. Indeed, archaeological data from these two regions are seldom compared – particularly those that concern the end of the Pleistocene between 60000 and 15000 BP (covering Marine Isotopic Stages 3 and 2).

The archaeological data from this period are generally associated with the end of the Middle Stone Age (MSA)-Middle Palaeolithic (MP) or the Late Stone Age (LSA)-Upper Palaeolithic (UP). The dynamics of the transition between these periods remain poorly defined and as broad entities, they exhibit a great deal of technical variability. Furthermore, the period was a time of great climatic variability characterised by a general tendency towards aridification (the ‘Big Dry’), punctuated by irregular periods of humidity. This climatic variability and its diverse regional environmental responses across the eastern part of the African continent may have posed major adaptive challenges to human populations.

This paper aims to examine the lithic variability documented for the end of the Pleistocene in both the Horn of Africa and north-eastern Africa, with a particular focus on technological change that occurred in the context of the MSA-MP/LSA-UP-LP transition and in relation to the variability within the LSA-UP-LP. The main trends are then compared between the two regions, allowing us to evaluate the presence of possible parallel techno-cultural trajectories in both regions.

**Keywords:** Horn of Africa, Nile valley, Late Pleistocene, lithic technology, transition.

**Résumé :** La Corne de l'Afrique et l'Afrique du Nord-Est présentent de nos jours un lien géographique naturelle le long du Nil et de ses affluents, plusieurs sources du Nil étant localisées dans la Corne. Cette connectivité a évolué tout au long du Pléistocène, et ses conséquences sur les interactions possibles entre les groupes humains de ces deux régions restent mal connues, malgré le rôle central de ces régions dans les questions de dispersion humaine au sein et hors d'Afrique. En effet, les données archéologiques issues de ces deux régions sont rarement comparées, surtout pour la période de la fin du Pléistocène, entre 60000 et 15000 BP (stades isotopiques marins 3 et 2).

Les données archéologiques de cette période sont généralement attribuées à la fin du Middle Stone Age (MSA)-Paléolithique moyen (PM) ou au Later Stone Age (LSA)-Paléolithique supérieur (PS). Les modalités des transitions MSA-MP/LSA-PS restent encore peu définies, et ces deux entités incluent une grande diversité technique. En outre, cette période correspond à une grande variabilité climatique caractérisée par une tendance générale vers une aridification du climat (« the Big Dry ») ponctuée irrégulièrement de périodes
plus humides. Cette variabilité climatique se traduit par des réponses environnementales différentes d'une région à l'autre, ce qui a probablement posé des défis d'adaptation importants pour les populations humaines de cette époque.

Cet article a pour objectif d'examiner la variabilité lithique de la fin du Pléistocène au sein de la Corne de l'Afrique d'une part et de l'Afrique du Nord-Est d'autre part, en portant une attention particulière aux changements technologiques dans le cadre des transitions MSA-PM/LSA-PS et de la variabilité au sein du LSA-PS. Les principales tendances identifiées seront ensuite comparées entre les deux régions, ces « regards croisés » nous permettons d'évaluer la présence d'éventuelles trajectoires technoculturelles parallèles aux deux régions.

**Mots-clés :** Corne de l'Afrique, vallée du Nil, Pléistocène récent, technologie lithique, transition.

# 1. INTRODUCTION

While the African continent occupies an important place in research on the origins and development of *Homo sapiens* during the second part of the Middle Pleistocene and the beginning of the Upper Pleistocene, the more recent prehistory of this continent, from 70 kya, remains comparatively little studied. This period is nonetheless key in the history of human evolution, constituting a major phase in the shaping of diversity in modern humans both at the biological and cultural level (see for example Mirazón Lahr, 2016; Pagani and Crevecoeur, 2019). The ANR Big Dry project (ANR-14-CE31-0023; Bon et al., this volume) was conceived and carried out in order to compensate for the lack of data relating to this period through an emphasis on eastern Africa, which occupies a key position in the population dynamics of *Homo sapiens* both within and outside of the continent (Molinaro and Pagani, 2018). In particular, the Horn of Africa (Ethiopia, Eritrea, Somalia, Somaliland and Djibouti) and north-eastern Africa (Egypt and Sudan; particularly those regions within the Nile Valley) exhibit a natural geographical connectedness along the Nile and its tributaries, many of which originate in the Horn (fig. 1). Despite the importance of identifying this spatial relationship within the archaeological data, particularly that pertaining to the period during which *Homo sapiens* dispersed out of Africa, the field data from these regions has rarely been compared. In particular, the question remains open as to whether this geographical link, and its development alongside the pronounced climatic shifts at the end of the Pleistocene, finds echoes within the cultural production of the populations of these regions.

Indeed, the Horn has most often been lumped in with regional studies of eastern Africa, in spite of the mounting evidence that speaks against the homogeneity of data from this large region, in particular between the Horn of Africa and the Great Lakes area of the Rift Valley (Lelongeon et al., 2020b; here: fig. 1). The act of comparing the recent Pleistocene prehistory of the Horn of Africa and of the Nile Valley, as intuitive as it may seem, is not without difficulty. Indeed, different research traditions have presided over the study of these two regions and guided the collection of diverse archaeological data, thus making any direct comparisons difficult even if only by the use of differing nomenclatures.

In order to approach this challenge, the first part of this article consists of a synthesis of the archaeological

documentation for each of these regions at the end of the Pleistocene and particularly for the period between 70 and 15 kya, taking into account new field data collected in the context of the ANR Big Dry project. Building on this foundation, the second part of the article aims to propose a series of comparisons related to the cultural trajectories observed in the Horn of Africa and north-eastern Africa, taking into account the strongly-contrasting paleo-environmental contexts of the two regions.

## 1.1. General palaeo-climatic context

The period in question stretches from the Marine Isotopic Stage (MIS) 4 to the beginning of MIS 1 (71-15 kya) and therefore overlaps significantly with the last glacial period. Although generally arid, this period is also characterised by strong climatic oscillations. MIS 4 and 3, for example, appear to have been punctuated by humid episodes, specifically at the beginning of MIS 4 and around 55-50 kya in eastern Africa, as well as around 45-35 kya in northern Africa (Blome et al., 2012). MIS 2, sometimes known as the 'Big Dry', encompasses notably the Last Glacial Maximum (LGM; ~ 23-19 kya; Waelbroeck et al., 2009). This was generally an arid period in eastern Africa, although it was straddled on both sides of the LGM – before 24 kya and after 18-16 kya – by more humid episodes (Gasse et al., 2008). The drying up of multiple East African lakes around ~ 16-17 kya, such as Lake Victoria (Stager et al., 2002) and Lake Tana (Lamb et al., 2007 and 2018) among others, had significant consequences on the flow and course of the White Nile, which almost completely dried up during parts of the year, and on the Blue Nile, which became a river with significant seasonality and a greatly-reduced flow (Williams, 2019 and 2020). These conditions contrast strongly with the environmental conditions of MIS 5, characterised by the formation of a mega-lake (> 45000 km²) on the White Nile from 110 kya onwards (Barrows et al., 2014). Despite the prevalence of more humid conditions at the beginning of MIS 2, as witnessed by the replenishing of subterranean waters in the eastern Sahara, North-eastern Africa is characterised by an even more arid (hyper-arid) climate during MIS 2, particularly during the LGM (Pachur and Hoelzmann, 1991; Abouelmagd et al., 2014).

In contrast, the end of MIS 2 and the beginning of MIS 1 coincide with the beginning of the African Humid Period (AHP; DeMenocal et al., 2000), marked by a distinct rise in precipitation in eastern Africa that allowed
<figure><img src="image_19.png" /><figcaption>**Fig. 1** – Map of the region considered in the paper, showing the geographical extension of the Nile Basin (after Williams, 2019, fig. 1) and Nubia (Auenmüller, 2019). Produced on QGIS v. 3.15 (QGIS Development Team, 2017) and Natural Earth Data. For site names, refer to figures 2 and 6 captions.</figcaption></figure>

**Fig. 1** – Carte de la région étudiée dans l'article, montrant l'extension géographique du bassin du Nil (d'après Williams, 2019, fig. 1) et de la Nubie (Auenmüller, 2019). Document créé avec QGIS v. 3.15 (QGIS Development Team, 2017) et Natural Earth Data. Pour les noms des sites, voir légendes des figures 2 et 6.
the reconnection of the White Nile with the Lake Victoria basin (Williams et al., 2006) and led to major flooding episodes on the Nile. However, the AHP is not a uniform and synchronous entity across the continent. North-eastern Africa for example exhibited an extremely arid climate until around 12-11 kya (Kuper and Kröpelin, 2006; also see discussion in Williams, 2019, p. 105).

This brief summary underlines the significant climatic and environmental variability in both time and space for these two regions. Our comparison will therefore aim to discern the ways in which these variations affected human populations in these areas by reflecting on potential complementarities between them during certain periods and, by contrast, if these two regions witnessed the development of distinct adaptation strategies in order to deal with different environmental challenges.

## 1.2. General techno-cultural context

Archaeological sites dated to the period between 70 and 15 kya testify to a significant diversity in their lithic assemblages, commonly categorised as Middle Palaeolithic (MP) or Middle Stone Age (MSA) at the beginning of the period, and Upper Palaeolithic (UP), Late Palaeolithic (LP) or Late Stone Age (LSA) at its end. While Palaeolithic (LP, MP, UP) terminology is used in north-eastern Africa, Stone Age terminology (MSA, LSA) is used in the Horn. The MP-MSA is broadly characterised by the use of a variety of core reduction methods, often aimed at exploiting core surfaces (such as the Levallois and Discoidal methods) for the production of flakes, and in certain cases blades and points. The primary retouched tools are retouched or shaped points, as well as scrapers. The LSA in the Horn is most often defined by the production of blades and bladelets associated with a miniaturisation of the toolkit. Backed tools frequently occupy an important place within assemblages, occasionally forming geometric shapes (such as segments). Burins as both tools and cores are equally common. In the Nile Valley, the UP is characterised instead by volumetric blade core reduction associated with a toolkit consisting primarily of retouched blades, whereas the LP may be distinguished on the basis of its bladelet production, often transformed into backed pieces, which are often retouched into geometries.

Whatever terminology is used (MSA-LSA or MP-UP/ LP), the Horn of Africa and the Nile Valley are sites of major technological transformations during the period between 70 kya and 15 kya.

## 1.3. Clarification of definitions

The MSA-MP is generally considered to stretch from 300 kya to 50 kya or even as late as 30 kya and up to the Holocene (e.g. Scerri et al., 2021). The LSA-UP extends from 50-30 kya up to the Holocene. The limits (both chronological and technological) between these different phases of the Palaeolithic are sometimes blurry. This is partly due to ambiguities that arise when dealing with the transition between the MSA-MP and the LSA-UP as they are far

from being abrupt or clean-cut. The starkest case is that of blade production industries at the end of the Pleistocene and the decision to consider them indicators of either the MSA-MP or the LSA-UP. This choice seems to mainly have its origins in the research histories of both regions. It is therefore pertinent to ask whether industries attributed to the MSA-MP by certain researchers would not be attributed to the LSA-UP by others and vice versa. In such a situation, it is important to go back to the definitions of core reduction methods, in particular the Levallois concept.

The Levallois concept has traditionally been seen as emblematic of the MSA-MP while displaying a wide technical diversity, notably through Levallois blade production. According to É. Boëda (1994 and 1995), Levallois core reduction is defined as a particular way of managing the volume of the core and its convexities involving hard-hammer and direct percussion, and resulting in predetermined removals of various shapes and sizes according to two broad modalities: preferential and recurrent. The Levallois concept is seen in cores composed of two opposing surfaces that are convex asymmetrical and hierarchized, with one side acting as the striking surface and the other as the production surface. The pieces are knapped along an axis parallel to the intersection of the two surfaces, making use of a striking platform whose preparation makes it perpendicular to the intersection of the surfaces. With the exception of Levallois débordant products linked to the management of lateral convexities, the Levallois concept as defined by É. Boëda (1994 and 1995) does not allow for the exploitation of the intersection of the core surfaces. This specification in the definition is fundamental for distinguishing between productions designed following a planimetric conception of core reduction (for example Levallois methods, planimetric in the sense of Van Peer et al., 2010) and those produced following a volumetric conception of core reduction organised around highly semi-circular geometries. This volumetric conception of core reduction is distinguished from the Levallois conception by virtue of its exploitation of a volume, implying the use of the total perimeter of the core whose production capacity is in theory equal to its volume. The so-called planimetric core reduction process (such as the Levallois) is rather limited to the productive exploitation of only one surface of the core (Boëda, 1990; Delagnes and Meignen, 2006). The distinction between these two conceptions – planimetric (or surface) and volumetric – is particularly meaningful to our perception of the evolution of lithic production between 70 kya and 15 kya, and therefore we make careful note of it in the following synthesis.

## 2. THE END OF THE PLEISTOCENE IN THE HORN OF AFRICA

The archaeological record in the Horn of Africa for the end of the Middle Pleistocene and Upper Pleistocene, i.e. from the MSA to the emergence of the LSA, exhibits numerous asynchronicities and local specificities in cul-
tural expression, as well as data of varying quality. Fur-
thermore, most known sites are concentrated primarily
within the Ethiopian Rift Valley system and its immediate
vicinity, leaving large areas of the Horn of Africa unex-
plored (fig. 2). Nevertheless, this synthesis will adopt a
malleable chronological and technical framework so as
to better explain the techno-cultural processes at work at
the end of the Pleistocene on the basis of the most reliable
data.

## 2.1. Emergence and decline of MSA technical traditions: transitions with permeable borders

A number of important sites in Ethiopia show that
the MSA had already fully developed within the Horn of
Africa before ~279 kya (Gademotta ETH-72-8B: Morgan
and Renne, 2008) and more broadly towards the end of
the Middle Pleistocene (KHS and AHS in Kibish: Shea,
2008; Kulkuletti ETH-72-1 and Gademotta ETH-72-7B:
Wendorf and Schild, 1974; Garba III: Mussi et al., 2014).

Although poorly studied, the oldest technologies already
exhibiting basic MSA characteristics can be seen much
earlier, around 500 kya (Brooks et al., 2018; Sánchez-De-
hesa Galán, 2020). *Homo sapiens* remains have also been
recovered from deposits dated to the end of the Middle
Pleistocene, min. 233 ± 22 kya (Kibish: McDougall et al.,
2005 and 2008; recently redated in Vidal et al., 2022) and
~ 160 kya (Herto: Clark et al., 2003). These were con-
sidered to be the oldest in Africa until the individuals
found at Jebel Irhoud in Morocco were dated to around
~300 kya (Hublin et al., 2017; Richter et al., 2017). How-
ever, in addition to these early sites with typical MSA
industries, other Ethiopian sites have produced Acheulean
industries with quite recent dates for this period, such as
at Mieso (~ 200 kya, De la Torre et al., 2014), as well
as industries exhibiting a combination of Acheulean and
MSA characteristics, such as at Herto (~ 160 kya, Clark
et al., 2003; Sahle et al., 2019). These assemblages recall
the inter-stratification of MSA (Sangoan) and Acheulean
industries dated between ~ 220 et ~ 150 kya at Sai Island
/site 8-B-11) in the Nile Valley (Van Peer et al., 2003 and

<figure><img src="image_20.png" /><figcaption>**Fig. 2** – Map of the Horn of Africa (extension of the Nile Basin after Williams, 2019, fig. 1): Location of main sites mentioned in the text.
Produced on QGIS v. 3.15 (QGIS Development Team, 2017) and Natural Earth Data.</figcaption></figure>

**Fig. 2** – **Carte de la Corne de l'Afrique (extension géographique du bassin du Nil d'après Williams, 2019, fig. 1) : localisation des principaux sites mentionnés dans le texte. Document créé avec QGIS v. 3.15 (QGIS Development Team, 2017) et Natural Earth Data.**
2004). The beginnings of the MSA towards the end of the Middle Pleistocene cannot therefore be seen as an abrupt and widespread technical change in the Horn of Africa. Rather, it must be seen as a gradual, asynchronous and patchy emergence over nearly 150 thousand years, during a time when the Acheulean was still predominant in certain areas.

The acceleration of the climatic oscillations and the increase in their amplitude from 500 kya onwards are often arguments to explain the cognitive and biological evolution of the genus *Homo* at the Acheulean-MSA transition, and during the course of the Middle Pleistocene as they adapted their ways of life to rapid and unpredictable environmental changes (Brooks et al., 2018; Potts et al., 2018; Scerri et al., 2018). In line with these hypotheses that place an emphasis on climatic variation as a motor for change, Brandt and colleagues (2017) suggest that the particularly cold and arid conditions of MIS 4 would have triggered a restructuring of the technical sphere as well as that of mobility, communication and group organisation. It is therefore possible that during the Upper Pleistocene, marked by the last glacial period (~110-15 kya), we may find the beginnings of changes leading to the decline of the MSA, which by the end of the LGM had given way completely to the LSA in the Horn of Africa.

At both the beginning or end of the MSA it seems that techno-cultural changes, which themselves may or may not have been shaped by environmental conditions, were the result of gradual complex and permeable processes as opposed to clear ruptures. While the full development of LSA technologies is already evident from the beginning of MIS 1 – with industries based on the production of blades, bladelets, burins and backed pieces – it seems that they must have partially co-existed with Late MSA technical traditions particularly visible in the use of Levallois methods and the presence of points, in some cases until the Holocene. However, the mixed MSA/LSA character of several of these industries from the Late Pleistocene and Early Holocene, often described as being transitional, should be considered in light of the often-unreliable contexts in which they were recovered and that may point to stratigraphic mixing between MSA and LSA layers. Despite their recurrence, it is therefore not proven beyond a doubt that the MSA/LSA transition can be characterised by such a techno-cultural form, or at least not uniformly across the Horn of Africa.

Going back further in time, the available MIS 3 site corpus for the region may well indicate local evolutions towards the new technologies of the LSA along heterogeneous trajectories. For this reason, it is unrealistic to expect a single model for the MSA/LSA transition for the whole of the Horn of Africa. Finally, the definitions of the MSA and LSA, simultaneously static at high resolution and imprecise at a more granular resolution, present an additional difficulty in discerning the transition mechanisms at the end of the Pleistocene. It is therefore necessary here to return to the available data in order to better contextualise this question.

## 2.2. Chronology and technologies of the MSA between MIS 5 and MIS 3

Any account of the human techno-cultural dynamics at the end of the Pleistocene in the Horn of Africa must consider the available data since MIS 5 (~130-71 kya), given the considerable number of sites attributed to the Upper Pleistocene that have not been precisely dated, as well as the processes of change that seem to have occurred over the *longue durée*. In general, comparisons made at the scale of the whole of eastern Africa show that the MSA in the Upper Pleistocene (also known as the Late MSA) is marked by a diversification of assemblage compositions and by the occupation by populations occupying more contrasting environments than during MIS 5 (Basell, 2008; Tryon and Faith, 2013; Blinkhorn and Grove, 2018). As an example, the oldest MSA coastal site in the Horn of Africa, Abdur Reef Limestone in Eritrea, is also dated to the beginning of MIS 5, at 125 ± 17 kya (Bruggemann et al., 2004).

MIS 5 in Ethiopia is represented by a series of open-air sites such as BNS (Bird's Nest Site), the most recent of the Kibish Formation, dated to 104 ± 1 kya (McDougall et al., 2005; Yellen et al., 2005). F. H. Brown and colleagues (2012) propose a correlation between the Aliyo Tuff of Member II of the Kibish Formation, dated to 104 ± 1 kya, and the tuff composing Unit 15 of Gademotta that directly covers the site ETH-72-6 (Wendorf and Schild, 1974). This correlation would place ETH-72-6 in MIS 5, despite a *terminus post quem* of ~183 kya (Morgan and Renne, 2008). In the Middle Awash, MSA assemblages contained in the Faro Daba Beds of the Halibee Member have an age constrained between ~106 and ~96 kyr, using U/$^{230}$Th burial dating of ostrich eggshell (OES; Niespolo et al., 2021). Uranium-Thorium dates from OES fragments at the site of SM1 in north-western Ethiopia, located along one of the main tributaries of the Blue Nile (the River Shinfa), provide an average date of around 75 kya, though the archaeological data are not yet published (Davis, 2019; Loewy et al., 2020).

A number of other sites may have an age that would place them towards the end of MIS 5 but that could equally be more recent, and are more generally considered to be Late MSA. One of these sites is A5 in the Aduma complex in the Middle Awash, which has an early date around ~90 kya obtained from the underlying sediments of Ardu B (Yellen et al., 2005). Another site, ETH-72-5 at Gademotta, is situated above Unit 15 already mentioned as dating to 104 ± 1 kya (Wendorf and Schild, 1974; Brown et al., 2012). The important site of Porc-Épic has provided only contradictory and unsatisfying dates, with estimations ranging between 75 and 61 kya (Michels and Marean, 1984), while other estimations place some MSA layers at the site around 50 kya (Yokoyama and Falgueres, unpublished but cited in Leplongeon, 2014) or between 40-25 kya (Assefa, 2006). This site exhibits a long sequence with MSA levels that could be attributed to either MIS 5, 4, or 3. The same goes for the site of K'one locality 5 extension, characterised by the Leval-
lois method of Nubian type, whose date of MIS 4 was estimated purely on the basis of sedimentological arguments that correlated the silts in which the artefacts had been recovered to an arid phase of the Upper Pleistocene (Kurashina, 1978; Brandt, 1986). In the upper part of the MSA levels in the cave of Midhishi 2, in Somaliland, a piece of charcoal produced a date of > 40 kya lying beyond the limit of the radiocarbon method, and indicating a minimal age during MIS 3 but which may in fact be much older (Brandt, 1986).

Archaeological data from the region corresponding to MIS 4 are practically non-existent. The Ethiopian site of Goda Buticha is one of the only sites to have yielded an absolute date that may be related to MIS 4. The date of around 63 ± 7 kya comes from the OSL dating of sediments from layer IIf at the bottom of the long sedimentary and archaeological sequence of the site (Tribolo et al., 2017). Nevertheless, the archaeological material unearthed in this layer was grouped together with the almost identical material from layers Ile and IId, dated respectively to 43 ± 5 kya and 24.8 ± 2.6 kya. This ensemble IId-IIf can therefore be attributed to the period between ~ 63 kya and ~ 25 kya, centered primarily on MIS 3 (Leplongeon, 2013; Leplongeon et al., 2017; here: fig. 3, no. 6). Similarly, the high-altitude site of Mochena Borago, located further south in Ethiopia, has produced MIS 3 industries in the Block Excavation Area dated between > 49 kya BP and ~ 36 kya cal. BP (Brandt et al., 2017; here: fig. 3, nos. 1-5). Even further to the south, another high-altitude site located at nearly 3,500 m above sea level, known as Fincha Habera, has delivered dates between ~ 47 kya and ~ 31 kya, corresponding to the end of MIS 3 (Ossendorf et al., 2019). Similar dates have been proposed for a series of open-air sites located in the Ziway-Shala basin in central Ethiopia (Deka Wede 1, Deka Wede 4, Bulbula 1 sector 3, Bulbula 4) that lie atop a layer dating to ~ 45-43 kya cal BP, thus attributed to the end of MIS 3 (Ménard and Bon, 2023). However, the only directly-dated site is that of Deka Wede 1 (DW1), for which two charcoal have produced dates between ~ 34 kya cal BP and 31 kya cal BP (Ménard et al., 2014, Douze et al., in prep.). In the Middle Awash, assemblages contained in the Wallia beds of the Halibee members have dates comprised between ~ 31-32 kyr and are attributed to the LSA, but their characteristics are not yet fully published (Niespolo et al., 2021). Finally, in the Rift Valley in southern Ethiopia, close to the Kenyan border, renewed excavations in the Gotera zone (Chavaillon and Chavaillon, 1985) may indicate the presence of sites attributed to MIS 4-3 (E. Spinapolice, pers. comm.; Fusco et al, 2021).

From a technological point of view, with the possible exception of the LSA in the Middle Awash, all lithic assemblages recovered between MIS 5 and MIS 3 can be considered fully MSA. They exhibit characteristics that were recurrent throughout the period (and that were already present from at least MIS 8), and that were employed in a variable manner by knappers at different sites. These characteristics are the use of Levallois methods following various modalities, the occasional use of

the Discoid method and, to a lesser extent, the implementation of a volumetric conception of core reduction. The objectives of the core reduction were primarily the production of flakes, but also of blades and points in various proportions and dimensions, some of which exhibit miniature dimensions (< 3 cm). Late MSA sites demonstrate the growing significance of blade production from both bidirectional opposed and unidirectional cores according either to a planimetric conception – as seen for instance at the Ziway-Shala MIS 3 sites (fig. 4) – or a volumetric conception. There is a wide range of retouched tools from the MSA in the Horn of Africa. Best represented are shaped or retouched points (unifacial, partly-bifacial or bifacial) that vary strongly in both morphology and typology (and probably function), as well as various types of scrapers made on diverse blanks, few end-scrapers, notched pieces and borers. Given that only one backed piece was discovered within the MSA levels of Goda Buticha (levels IId-IIf) as well as several fragments of backed tools at Mochena Borago (T-Group), it is difficult to draw any conclusions about the importance of this type of retouched tool in the context of MIS 3 (Brandt et al., 2017; Leplongeon et al., 2020a).

Further characteristics of these Late MSA industries are visible on a more local level. In south-eastern Ethiopia for instance, the sites of Porc-Épic and Goda Buticha exhibit almost no evidence for the production of unremented points and instead a preponderance of retouched points of highly-diversified typologies (Perlès, 1974; Pleurdeau, 2005 and 2004; Leplongeon, 2013; Leplongeon et al., 2017; here: fig. 3, no. 6). This contrasts strongly with K'one locality 5 extension, located in the north of the Main Ethiopian Rift, where Nubian Levallois methods for the production of technological points dominate. The sites of Mochena Borago and Fincha Habera in southern Ethiopia show evidence for bipolar-on-anvil production on small obsidian blocks within the assemblages (Brandt et al., 2012 and 2017; Ossendorf et al., 2019; here: fig. 3, no. 4), a feature poorly documented in other areas. Similarly, the production of flakes of small dimensions (≤ 3 cm) at the site of Aduma 5, in the Middle Awash, is claimed to be a local variation and led to the introduction of new terminology such as “micro-Levallois” and “micro-Aduma” core types (Yellen et al., 2005). Finally, the Ziway-Shala MIS 3 sites are characterised by bidirectional opposed recurrent Levallois core reduction for blade, elongated flake and point production, showing very finely-crafted faceting of the striking platforms, as well as large pieces with convergent edges with inverse basal thinning (Ménard et al., 2014).

This mosaic of technological specificities draws on a common source and seems to exhibit local cultural adaptations of the MSA that can be identified in geographically-distinct zones dispersed across the Horn of Africa at both individual sites and in local groupings. Despite the difficulty of assessing the chronological relations between sites in certain cases, the idea that environmental conditions played a role in these local expressions finds an echo in the “kaleidoscope of palaeoenvironments”
<figure><img src="image_21.png" /></figure>

**Fig. 3** – Examples of artifacts from MIS 3 sites from the Horn of Africa. 1: Double platform core, Mochena Borago, Goup-S (drawing and terminology after Brandt et al., 2012); 2: Multiplatform core, Mochena Borago, Group-T (drawing and terminology after Brandt et al., 2012); 3: Partly-bifacial point, Mochena Borago, Group-T (drawing and terminology after Brandt et al., 2012); 4: Bipolar core, Mochena Borago, Group-S (drawing and terminology after Brandt et al., 2012); 5: Backed piece, Mochena Borago, Group-T (drawing and terminology after Brandt et al., 2012); 6: Bifacial point, Goda Buticha, layers IId Iff (drawing A. Leplongeon); 7-8: Bidirectional cores on flake, Deka Wede 4 (photos K. Douze); 9: Bidirectional elongated flake, Deka Wede 4 (photo K. Douze); 10-11: Blades, Deka Wede 4 (photos K. Douze); 12: Retouched tool with basal thinning, Deka Wede 4 (photo K. Douze); 13: Convergent bidirectional flake, Deka Wede 4 (photo K. Douze). All in obsidian except no. 6 in flint.

**Fig. 3** – Exemples d'artefacts découverts dans des sites MIS 3 de la Corne de l'Afrique. 1 : Nucléus à double plan de frappe, Mochena Borago, Goup-S (dessin et terminologie d'après Brandt et al., 2012) ; 2 : nucléus à multiples plans de frappe, Mochena Borago, Group-T (dessin et terminologie d'après Brandt et al., 2012) ; 3 : pointe parti-bifaciale, Mochena Borago, Group-T (dessin et terminologie d'après Brandt et al., 2012) ; 4 : nucléus bipolaire sur enclume, Mochena Borago, Group-S (dessin et terminologie d'après Brandt et al., 2012) ; 5 : pièce à dos, Mochena Borago, Group-T (dessin et terminologie d'après Brandt et al., 2012) ; 6 : pointe bifaciale, Goda Buticha couches IId Iff (dessin A. Leplongeon) ; 7-8 : nucléus bidirectionnels sur éclat, Deka Wede 4 (clichés K. Douze) ; 9 : éclat allongé bidirectionnel, Deka Wede 4 (cliché K. Douze) ; 10-11 : lames, Deka Wede 4 (clichés K. Douze) ; 12 : outil retouché à amincissement basal, Deka Wede 4 (cliché K. Douze) ; 13 : éclat convergent bidirectionnel, Deka Wede 4 (cliché K. Douze).

Tous en obsidienne sauf numéro 6 en silex.
described by M. Pickford (2009) to characterise the east-
ern African Rift and its surrounding area. Over the course
of the Upper Pleistocene, given the relentless degradation
of climatic conditions – in particular from MIS 4 onwards
– the Horn would have offered a diversity of habitats in
limited spaces that may have encouraged local adapta-
tions. In this context, the range of geological zones occu-
pied (Asrat et al., 2008), from the Rift floor shaped by
intense volcanic activity (the sites of Ziway-Shala) to the
Jurassic limestone cliffs at the junction of the Somalian
plateau and the Afar (Goda Buticha, Porc-Épic) and to
the silicic mountains of the rift escarpments (Mochena
Borago, Fincha Habera), is without doubt partly respon-
sible for the diversity of technical behaviours observed,
in addition to the various locally available and dominant
raw materials (for example Pleurdeau, 2005; Ossendorf
et al., 2019; Fusco et al., 2021).

Whereas all MSA sites dating to the end of the Mid-
dle Pleistocene, and certainly most of those from MIS 5,
are open-air settlements, numerous sites dating to MIS
4/3 and MIS 3 are cave and shelter occupations, occa-
sionally located in high-altitude zones (> 2000 m). These
latter sites offer a range of vertically-distributed ecozones
favourable to occupation by small groups of hunter-gath-
erers, and do not require seasonal movements over long
distances (Vogelsang and Wendt, 2018; Ossendorf et al.,
2019). In the same way, lakeshores also functioned as
"magnets for occupation" during the MSA. It was the case
in the endorheic basin of Ziway-Shala, which despite its
low water level during MIS 3 nonetheless experienced a

period of landscape stabilisation with occupations con-
centrated on the basin floor, riverbanks or on canyon
slopes (Bon et al., 2013; Ménard et al., 2014). While the
Horn of Africa – and in particular the Rift Valley – may
be perceived as a favourable context for human expan-
sion, the archaeological record in the area as it appears
now, suggests a series of isolated occupations over long
periods of time.

2.3. MIS 2 and the question
of MSA/LSA transitional industries

The MIS 2, as recorded for example in the lake sed-
iments of Chew Bahir in Ethiopia, contained periods of
(hyper-)aridity and perhaps more importantly episodes of
rapid and relatively abrupt arid-humid oscillation (Trauth
et al., 2019). The impact of these particular MIS 2 cli-
matic and environmental conditions on human popu-
lations remains difficult to evaluate due to the lack of
archaeological data from this period. Furthermore, sev-
eral site sequences are characterised by a sedimentary
hiatus corresponding to this period (Goda Buticha and
Mochena Borago: Pleurdeau et al., 2014; Brandt et al.,
2017; Tribolo et al., 2017). The hypothesis in which the
mountainous plateaux of south-western Ethiopia acted
as a refuge for human populations during this period
(Brandt et al., 2012; Foerster et al., 2015, p. 337) has
recently been the subject of renewed attention. On the
one hand, the stratigraphic sequence of Mochena Borago
(situated around 2,200 m a.s.l on Mount Damota) does

<figure><img src="image_22.png" /><figcaption>Fig. 4 – Operation scheme for blade production at the MIS 3 sites of B1s3 et DW1, Ziway-Shala basin
(Ménard et al., 2014; CAD C. Ménard).</figcaption></figure>

<caption>**Fig. 4** – Schéma opératoire de production luminaire à B1s3 et DW1, sites MIS 3 du bassin de Ziway-Shala
(Ménard et al., 2014 ; DAO C. Ménard).</caption>
not exhibit any MIS 2 level (Brandt et al., 2017). On the other hand, Sodicho Rock Shelter located around 40 km from Mochena Borago at 1,900 m altitude a.s.l. exhibits a long stratigraphic sequence dating to MIS 2 and associated with human occupations, from which the material is currently in the process of being published (Hensel et al., 2019 and 2021). The sedimentary data from the site of Sodicho suggests an occupation of the site when arid conditions are documented in the region, supporting the environmental refugium hypothesis during MIS 2 for at least one part of the mountainous plateaux of south-western Ethiopia. In contrast, the sedimentary sequence at the site from 17 kya cal. BP testifies to more humid conditions that could be correlated to the AHP, and which correspond largely with sterile archaeological units, suggesting an abandonment of the site by humans.

Between the industries that come before and after MIS 2 there are significant technical changes. The underlying question is the one of the emergence of the LSA in the Horn of Africa, which seems to occur relatively late (during the MIS 2) in this region. It is therefore important to identify if the changes linked to this emergence, particularly technical ones, appear in rupture or in continuity with the MSA. From the mid-twentieth century, it was considered that a transitional period between the MSA and LSA was apparent in the Horn of Africa, given repeated discoveries of assemblages with both MSA and LSA characteristics, with Levallois and Discoidal products as well as shaped or retouched points occurring alongside large backed tools, microliths, and significant (often predominant) blade productions. This association of elements led J. D. Clark to propose a distinct regional nomenclature for these assemblages that he considered as markers of the end of the Upper Pleistocene, between the MSA and the LSA, during an arid period (Clark, 1954, p. 158). These included the Hargeisan in northern Somalia, which he considered to be a distinct variant of the Magosian of southern Somalia and the Ogaden – due to differences in the types of angle burins and end-scrapers in particular – and as a successor to the Stillbay, which according to the author was the last MSA culture. Given the scarcity of sites relating to this Hargeisan “culture” – an issue acknowledged by J. D. Clark – the use of the term “Hargeisan” as a cultural-historical entity was little by little abandoned despite occasionally still being used (Brandt and Gresham, 1990; Gutherz et al., 2014). Since then, many of these assemblages with transitional characteristics have been re-studied and others revealed, though with questionable sedimentary contexts that do not always allow their transitional nature to be confirmed.

The review of the few sites in the Horn of Africa with assemblages composed of both MSA and LSA elements – and therefore potentially transitional – reveals that they most often occurred during MIS 2, and have often uncertain chrono-stratigraphic contexts. In Somaliland, assemblages attributed to the Hargeisan were recovered from Unit CSUb at Midhishi 2 dated to around 1890 ± 340 BP (Brandt, 1986), as well as at Laas Geel Shelter 7, where layers SU709-SU7011 provided conflicting dates between

the 13th millennium cal BP and 40 kya BP (Gutherz et al., 2014). In Ethiopia, the site of Aladi Springs delivered an assemblage associating typical MSA and LSA artefacts, which was already described as unreliable by J. D. and K. D. Williamson (1984) and whose age is uncertain though possibly a little older than ~ 17-12 kya BP, according to the date obtained for the clayey layers directly above (Gossa et al., 2012). The lower horizon at site FeJx4 from Lake Besaka was considered to be MIS 2, with dates between 27120-21850 cal. BP (Brandt, 1986), placing it among the oldest expressions of the LSA in Ethiopia (also see Gasse and Street, 1978). A new date produced in the context of the ANR Big Dry indicates a minimum age of around ~ 13.6-13.4 kya cal. BP, which leaves open the hypothesis that the context is potentially younger (Habte, 2020).

It is clear that the corpus of sites with so-called transitional industries as well as absolute dates within MIS 2 are rather unconvincing (see also Leplongeon et al., 2020b). As mentioned earlier, it is only recently that two new sites with contexts reliably-dated to MIS 2 were discovered, which are currently in the process of being published. These include the site of Sodicho, located in south-western Ethiopia (Hensel et al., 2019 and 2021), the Oulen Dorwa assemblages in the Middle Awash (Niespolo et al., 2021) and the side of Aga Dima S2 (ADS2) in the Ziway-Shala Basin.

The material from the site of Sodicho is in the process of being published, but a preliminary description of the lithic assemblage from part of the lower levels of the sequence, dated between ~ 27-13.5 kya cal. BP, shows dominant bladelet production. No retouched tools were identified in the studied sample (Hensel et al., 2021, p. 12; here: fig. 5, nos. 1-3). Similarly, the material from the Oulen Dorwa assemblages in the Middle Awash is in the process of being analysed. It is attributed to the LSA and is associated with numerous OES fragments, ¹⁴C dated to between 23.9 and 21.4 kya cal. BP (Niespolo et al., 2021). The characteristics of the lithic assemblages appear at first sight broadly similar to the ones of Sodicho (bladelet production from pyramidal cores, with few retouched tools), but both assemblages need to be further characterised before they can be included in comparative analyses.

The site of ADS2 is a sedimentary trap whose lower layers (b to d) are reliable and dated between ~ 31-26 kya cal. BP, at the MIS 3-MIS 2 boundary (Habte, 2020; Douze et al., in prep.). The lower part of the sequence of ADS2 is probably both contemporaneous (level d) with and successive (levels c and b) to the sites dated to the end of MIS 3 in the Ziway-Shala Basin (DW1, DW4, B1s3, B4) located a few kilometers away and below. Elevated slightly above its surroundings, Aga Dima may have been occupied during the minor lake transgression recorded in the Deka Wede and related to the turning point between MIS 3-MIS 2, a phase during which the MIS 3 sites situated by the river were submerged. The question is whether this slight temporal stagger is enough to explain how a technical industry so strongly anchored in the know-
<figure><img src="image_23.png" /><figcaption>**Fig. 5.** Examples of artifacts from MIS 2 sites from the Horn of Africa. 1-3: Bladelet cores, Sodicho, Late Pleistocene (drawings and terminology after Hensel et al., 2021); 4-5: Volumetric small elongated flake cores, Aga Dima S2, Level c (photos K. Douze); 6: Bidirectional core on flake, Aga Dima S2, Level d (photo K. Douze); 7: Bidirectional core on flake, Aga Dima S2, Level c (photo K. Douze); 8: Elongated bidirectional flake, Aga Dima S2, Level c (photo K. Douze); 9: Blade, Aga Dima S2, Level c (photo K. Douze); 10: Bidirectional point with basal thinning, Aga Dima S2, Level d (photo K. Douze); 11: Elongated flake with basal thinning, Aga Dima S2, Level c (photo K. Douze); 12: Backed bladelet, Aga Dima S2, Level d (photos K. Douze); 13: Backed bladelet, Aga Dima S2, Level c (photos K. Douze). All in obsidian.</figcaption></figure>

<caption>**Fig. 5** – Exemples d'artefacts de sites MIS 2 de la Corne de l'Afrique. 1-3 : Nucléus à lamelles, Sodicho, Pléistocène final (dessins et terminologie d'après Hensel et al., 2021) ; 4-5 : petits nucléus volumétriques à éclats allongés, Aga Dima S2, niveau 6 (clichés K. Douze) ; 6 : nucléus bidirectionnel sur éclat, Aga Dima S2, couche d (cliché K. Douze) ; 7 : nucléus bidirectionnel sur éclat, Aga Dima S2, couche c (cliché K. Douze) ; 8 : éclat bidirectionnel allongé, Aga Dima S2, couche c (cliché K. Douze) ; 9 : lame, Aga Dima S2, couche c (cliché K. Douze) ; 10 : pointe bidirectionnelle à amincissement basal, Aga Dima S2, couche d (cliché K. Douze) ; 11 : éclat allongé à amincissement basal, Aga Dima S2, couche c (cliché K. Douze) ; 12 : lamelle à dos, Aga Dima S2, couche d (cliché K. Douze) ; 13 : lamelle à dos, Aga Dima S2, couche c (cliché K. Douze). Tous en obsidienne.</caption>
hows of the MSA could be subsequently accompanied by a new, typically LSA component at ADS2.

At ADS2, the blade character of the industry – already present during MIS 3 at the neighboring sites on the lacustrine plain (DW1, DW4, B1s3, B4) – is further reinforced by the presence of blades and bladelets that are more centered and straight, resulting from more volumetric core reductions (fig. 3, nos. 10 and 11; fig. 5, no. 8). The presence of tools with basal thinning as well as unifacial and partly-bifacial points that form the third most important group of tools at ADS2 testify to a strong similarity with the MIS 3 sites of the lacustrine plain (fig. 3, no. 12; fig. 5, nos. 10 and 11). However, the backing process, i.e. for the manufacture of backed tools and truncated pieces, is represented in the assemblages of ADS2 while being completely absent from older sites in the same area (fig. 5, nos. 12 and 13). The backing process was nonetheless carried out just as much on large blanks of the same type as those produced at the end of the MSA, as on bladelets, with the latter present only in small quantities sometimes reaching small dimensions (≤ 3 cm long). The use of flakes or blades as blanks for cores is a common feature across all sites, although at ADS2 removals are also concentrated on the edges of these core blanks for the production of bladelets on the narrow surface, aside from real burins that also appear for the first time (11% of all tools). The blades are more robust and narrow than those obtained from the planimetric conception of core reduction. The bidirectional exploitation, which is common to all the sites of the Ziway-Shala basin (fig. 3, nos 7 and 8; fig. 5, nos. 6 and 7) is also implemented through a volumetric conception of core reduction at ADS2. The half-crest blades are also more numerous. Together, these elements suggest a gradual technological and typological shift that introduces, for the first time in the Ziway-Shala area, elements that are undoubtedly characteristic of the LSA (volumetric debitage, significant production of burins and backed pieces; Ménard, 2015; Habte, 2020). The association of these techno-typological characteristics makes attributing this site to either the MSA or LSA quite difficult, though it is tempting to see it as Early LSA with a Late MSA technical persistence. The stratigraphic truncation of the sediments after 26 kya cal BP at ADS2, as well as the absence of published lithic data for the period between 26 and 15 kya here or elsewhere in the Horn of Africa (beyond the brief description of Sodicho, Hensel et al., 2021) prevents us from evaluating whether the later LSA industries are in cultural continuity with the LSA components of the ADS2 industries, both being chronologically separated by more than 10 millennia, even at a local scale.

Given the poor resolution of the archaeological documentation for MIS 2, it is difficult to know whether the extreme aridity of MIS 2 rendered human occupation in the Horn of Africa invisible, or if it caused populations to abandon the region. The recently published data from Sodicho (Hensel et al., 2021) attest to a retreat of populations towards refuge zones, more of which may be identified in the future. In any case, our understanding of the

processes of decline of MSA technical traditions and the subsequent rise of LSA technical systems during this isotope stage has been strongly impacted by these climatic changes and yet the processes of this shift are difficult to grasp. The site of ADS2 nonetheless shows that before the LGM, at least locally, certain techniques that were to become characteristic of the LSA were already present, whereas later in the same area, no techno-typological similarity with the MSA is observed after the LGM, during MIS 1 (Ménard et al., 2014). As for Sodicho, although the authors do not propose a taxonomical attribution for the assemblages of MIS 2, it is nonetheless clear that these assemblages, which remain to be described, will deliver precious information regarding this issue.

## 2.4. Synthesis of the contribution of the Big Dry project to the question of the MSA-LSA transition in the Horn of Africa

Our studies, together with the other available data, allow a new look at the MSA-LSA transition by questioning the meaning of the presence and/or absence of certain elements considered as techno-cultural markers, such as 1) backed pieces and microlithism, 2) blade production, and 3) Levallois core reduction and points.

In general, backed pieces occur very occasionally in pre-MIS 1 contexts (Leplongeon et al., 2020a). The only sites where backed pieces have been found in contexts securely dated to MIS 3 are Mochena Borago, where they appear in the form of tool fragments (Brandt et al., 2012 and 2017; here: fig. 3, no. 5), and Goda Buticha IId-IIf (N = 1; Leplongeon, 2014; Leplongeon et al., 2017), where such pieces may be the result of intrusions from LSA layers immediately above. In contrast, the site of ADS2, dated to the beginning of MIS 2, has provided a small number of backed pieces (n = 18/385 retouched pieces) made on varied blank types and of varying dimensions (fig. 5, nos. 12 and 13). These backed pieces are made either on blanks that are very similar to those produced at MSA sites from the end of MIS 3 in the area, namely on large elongated pieces resulting from bidirectional opposed core reduction, or on bladelets from which one of the cutting edges has been modified by abrupt retouch. These data seem to indicate that the emergence of this type of modification occurs towards the end of the Pleistocene in the Horn of Africa, possibly associated with the emergence of LSA technical systems. However, and this is an important fact, it can be dissociated from the emergence of what has been traditionally named “microlithism” (Leplongeon, 2014).

Indeed, the miniature dimensions (≤ 3 cm) of a significant proportion of the artefacts from certain assemblages is a common feature at several Late MSA sites for the production of flakes and bladelets (for example Aduma A5, Porc-Épic, Mochena Borago, Goda Buticha) and is already apparent during the Early MSA for flake productions (for example Kibish, Gademotta ETH-72-8B, Garba III). The production of tools of very small