# The human remains found in 1967 in Axlor: Still not convincingly Neandertals: A reply to González-Urquijo et al

Asier Gómez-Olivencia, Diego López-Onaindia, Nohemi Sala, Antoine Balzeau, Ana Pantoja-Pérez, Ignacio Arganda-Carreras, Mikel Arlegi, Joseba Rios-Garaizar, Aida Gómez-Robles

<figure><img src="image_1.png" /></figure>

## To cite this version:

Asier Gómez-Olivencia, Diego López-Onaindia, Nohemi Sala, Antoine Balzeau, Ana Pantoja-Pérez, et al.. The human remains found in 1967 in Axlor: Still not convincingly Neandertals: A reply to González-Urquijo et al. American Journal of Biological Anthropology, 2023, 180 (2), pp.245-251. 10.1002/ajpa.24633. hal-03985684

HAL Id: hal-03985684

https://hal.science/hal-03985684

Submitted on 19 Oct 2023

HAL is a multi-disciplinary open access
archive for the deposit and dissemination of sci-
entific research documents, whether they are pub-
lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
scientifiques de niveau recherche, publiés ou non,
émanant des établissements d'enseignement et de
recherche français ou étrangers, des laboratoires
publics ou privés.

<figure><img src="image_2.png" /></figure>
<figure><img src="image_3.png" /></figure>

The human remains found in 1967 in Axlor: still not convincingly Neandertals. A reply to González-Urquijo et al.

<table><tr><td>Journal:</td><td>American Journal of Biological Anthropology</td></tr><tr><td>Manuscript ID</td><td>AJPA-2022-00017.R1</td></tr><tr><td>Wiley - Manuscript type:</td><td>Letter to the Editor</td></tr><tr><td>Date Submitted by the Author:</td><td>n/a</td></tr><tr><td>Complete List of Authors:</td><td>Gómez-Olivencia, Asier; Sociedad de Ciencias Aranzadi, Departamento de Prehistoria; Universidad del País Vasco Facultad de Ciencia y Tecnología, López-Onaindia, Diego; Autonomous University of Barcelona (UAB), Biologia Animal, Biologia Vegetal i d'Ecologia Sala, Nohemi; Centro UCM-ISCIII de Investigación sobre la Evolución y Comportamiento Humanos Balzeau, A; Museum Natl Hist Nat, Dept Prehist, CNRS UMR 7194 du CNRS, Paris, France, Dept. of Prehistory Pantoja-Pérez, Ana; Centro UCM-ISCIII de Investigación sobre la Evolución y Comportamiento Humanos Arganda-Carreras, Ignacio; Dept. Ciencias de la Computacion e Inteligencia Artificial. Facultad de Informatica, Universidad del País Vasco-Euskal Herriko Unibertsitatea (UPV/EHU) Manuel Lardizabal Ibilbidea 1, 20018 Donostia, Gipuzkoa, Spain. Arlegi, Mikel; Universidad del País Vasco, Estatigrafía y Paleontología Rios-Garaizar, Joseba; CENIEH Gómez-Robles, Aida; Konrad Lorenz Institute for Evolution and Cognition Research</td></tr><tr><td>Key Words:</td><td>&lt;i&gt;Homo sapiens&lt;/i&gt;, Neandertal, geometric morphometrics</td></tr><tr><td>Subfield: Please select 2 subfields. Select the main subject first.:</td><td>Paleontology, Human biology [living humans; behavior, ecology, physiology, anatomy]</td></tr></table>
Letter to the Editor

The human remains found in 1967 in Axlor: still not convincingly Neandertals. A reply to
González-Urquijo et al.

Asier Gómez-Olivencia<sup>a,b,c*</sup>

Diego López-Onaindia<sup>d</sup>

Nohemi Sala<sup>e,c</sup>

Antoine Balzeau<sup>f,g</sup>

Ana Pantoja-Pérez<sup>e,c</sup>

Ignacio Arganda-Carreras<sup>h,i,j</sup>

Mikel Arlegi<sup>k,l</sup>

Joseba Rios-Garaizar<sup>m</sup>

Aida Gómez-Robles<sup>n,o,p</sup>

<footnote><sup>a</sup>Dept. Geología, Facultad de Ciencia y Tecnología, Universidad del País Vasco/Euskal Herriko Unibertsitatea (UPV/EHU). Barrio Sarriena s/n, 48940 Bilbao, Spain.</footnote>

<footnote><sup>b</sup>Sociedad de Ciencias Aranzadi, Zorroagagaina 11, 20014 Donostia-San Sebastian, Spain.</footnote>

<footnote><sup>c</sup>Centro UCM-ISCIII de Investigación sobre Evolución y Comportamiento Humanos, Avda. Monforte de Lemos 5 (Pabellón 14), 28029 Madrid, Spain.</footnote>

<footnote><sup>d</sup>UMR 5199, PACEA, Université de Bordeaux, Allée Geoffroy Saint-Hilaire, Bâtiment B8, CS50023 33615 Pessac Cedex, France.</footnote>

<footnote><sup>e</sup>Centro Nacional de Investigación sobre la Evolución Humana (CENIEH), Paseo de la Sierra de Atapuerca 3, 09002 Burgos, Spain.</footnote>
fÉquipe de Paléontologie Humaine, UMR 7194, CNRS, Département Homme et Environnement, Muséum national d'Histoire naturelle. Musée de l'Homme, 17, Place du Trocadéro, 75016 Paris, France.

gDepartment of African Zoology, Royal Museum for Central Africa, Tervuren, Belgium.

hDept. Ciencias de la Computación e Inteligencia Artificial. Facultad de Informatica, Universidad del País Vasco/Euskal Herriko Unibertsitatea (UPV/EHU) Manuel Lardizabal Ibilbidea 1, 20018 Donostia, Gipuzkoa, Spain.

iIkerbasque, Basque Foundation for Science, Bilbao, Spain.

jDonostia International Physics Center (DIPC). Manuel Lardizabal Ibilbidea 4, 20018 Donostia, Gipuzkoa, Spain.

kInstitut Català de Paleoecologia Humana i Evolució Social (IPHES-CERCA), Zona Educacional 4, Campus Sescelades URV (Edifici W3), 43007 Tarragona, Spain.

lUniversitat Rovira i Virgili, Departament d'Història i Història de l'Art, Avinguda de Catalunya 35, 43002 Tarragona, Spain.

mIndependent researcher.

nDepartment of Anthropology, University College London, WC1E 0BW London, UK.

oDepartment of Genetics, Evolution and Environment, University College London, WC1E 6BT London, UK.

pDepartment of Life Sciences, Natural History Museum, SW7 5BD London, UK.

Correspondence

Asier Gómez-Olivencia, Dept. Geología, Facultad de Ciencia y Tecnología, Universidad del País Vasco/Euskal Herriko Unibertsitatea (UPV/EHU). Barrio Sarriena s/n, 48940 Bilbao, Spain.

Email: asier.gomezo@ehu.eus (A.G.-O.)
ORCID

Asier Gómez-Olivencia https://orcid.org/0000-0001-7831-3902

Diego López-Onaindia https://orcid.org/0000-0002-5266-6416

Nohemi Sala https://orcid.org/0000-0002-0896-1493

Antoine Balzeau https://orcid.org/0000-0002-4226-611X

Ana Pantoja-Pérez https://orcid.org/0000-0001-9302-1756

Ignacio Arganda-Carreras https://orcid.org/0000-0003-0229-5722

Mikel Arlegi http://orcid.org/0000-0001-5665-9275

Joseba Rios-Garaizar https://orcid.org/0000-0001-8474-2156

Aida Gómez-Robles https://orcid.org/0000-0002-8719-2660
In 2020, we published a study that described all the human remains found during J. M. de Barandiarán's excavations in Axlor (Dima, Biscay). Our study first presented two deciduous teeth and a parietal fragment found in an undisturbed Mousterian context, all of which show morphological features consistent with a Neandertal classification (Gómez-Olivencia et al., 2020; Supplementary Text S1). Our study also reassessed the human remains previously described by Basabe (1973), likely belonging to a single individual and traditionally classified as a Neandertal (see e.g., Rostro Carmona, 2013). However, our metric and morphological assessment suggested stronger affinities with modern humans. Recently, a reply to our article has been published, focusing on the remains previously published by Basabe (1973). In their reply, González-Urquijo, Bailey, & Lazuen (2021: 553) state that “Axlor’s level IV human remains are convincingly Neanderthals”, thus concluding that our taxonomic classification “is not supported by the anatomical evidence” and that the “balance of the evidence-morphological and stratigraphic-is most consistent with a Neandertal classification for these teeth” (González-Urquijo et al., 2021: 557). These authors take issue with two aspects: the taxonomic classification of the human remains found in 1967 and the discussion and reinterpretation of the stratigraphic context of these remains.

Here we address the points raised by González-Urquijo et al. (2021).

# 1 The taxonomic attribution of the human remains found in 1967

The human remains found in 1967 comprise four teeth (left P⁴-M³) found on September 7th 1967 in the square 13F at a depth of 265 cm. Two of these teeth (M¹ and M²) were found in a maxillary fragment. Additionally, a left canine was found on September 8th in the square 13E at a depth of 285 cm (Gómez-Olivencia et al., 2020: Figure S6). Two of these teeth (the C' and the M²) are currently lost, and therefore, our taxonomic assessment was based on the P⁴, M¹ and M³. All these remains were originally attributed to the Mousterian level III by Barandiarán (Barandiarán, 1980; see also Gómez-Olivencia et al., 2020: Figure S6). However, based on the depth of the findings and the depth attributed by Barandiarán to the level IV in 1968 (Barandiarán, 1980), they
have been later and repeatedly attributed to level IV (Basabe, 1982; González Urquijo, Ibáñez Estévez, Ríos Garaizar, & Bourguignon, 2006; Lazuen Fernández & González-Urquijo, 2019-2020).

González-Urquijo et al. (2021: 553) oversimplified our taxonomic assessment, stating that we concluded that “those remains should instead be assigned to a single Upper Paleolithic *Homo sapiens* individual”. However, our study states that “based on both morphological and size characteristics, this individual shows stronger affinities with modern humans than with Neandertals” (Gómez-Olivencia et al., 2020: 486), while we also clearly recognized that some of the teeth (e.g., the canine and the P⁴) showed some features that are present in high percentages in Neandertals, but are not exclusive of this group. In our discussion, we hypothesized that “these human remains could belong to an UPMH [Upper Paleolithic modern human], which should be tested in the near future using direct C14 datings”. This claim was based on the results of our morphometric analyses, the absence of Holocene recent prehistory remains from the Axlor sequence and the presence of an early Upper Paleolithic occupation in the site (Gómez-Olivencia et al., 2020: 488). This was summarized in our abstract, which states that the teeth from Axlor “may represent one of the scarce examples of Upper Paleolithic modern human remains in the northern Iberian Peninsula, which should be confirmed by direct dating” (Gómez-Olivencia et al., 2020: 475). Thus, we suggested that these remains may have belonged to an UPMH, the confirmation of which would require further analyses, but we did not discard other possibilities, such as these teeth having a more recent chronology.

## 2 Dental morphological analysis

González-Urquijo et al. (2021) disagree with some of our morphological assessments and take issue with the employed methodology. The taxonomic assessment of the Axlor 1967 remains by González-Urquijo et al. (2021) pivots mainly around the morphology of the lost canine, the crown morphology of the P⁴ and the morphology of the M¹.
Firstly, González-Urquijo et al. conclude that “the morphological features of the Axlor teeth seem to be either Neanderthal-like or ambiguous, but there is no reason to suggest these teeth belong to *H. sapiens*”. Their comments on our taxonomic assessment are limited to the crown morphology; they do not comment on other features that can be of taxonomic interest (e.g., the root morphology or the P⁴), nor do they attempt to carry out additional analyses despite the original micro-CT scans being publicly available.

González-Urquijo et al. (2021: 553) agree with us that the teeth from Axlor are small but they disregard this information as they consider that crown size is a poor discriminator between Neandertals and *Homo sapiens*. The dimensions of the Axlor samples are closer to the Upper Paleolithic *Homo sapiens* (HS) means (C', P⁴) or to the recent HS means (M¹, M², M³) than to Neandertals. The published BL measurements of the lost M² are below (and outside) our Neandertal and UP range of variation. In addition, our size assessment was complemented with shape information (i.e., form analysis). Geometric morphometric analysis of form variation (including size and shape) is a widely used way to assess taxonomic affinity (Compton et al., 2021; Garralda et al., 2020), and it yielded informative results in some teeth from Axlor (M¹ and M³) but not in others (P⁴), as we clearly stated in our study (Gómez-Olivencia et al., 2020).

González-Urquijo et al. (2021: 553) also consider that the grades of expression of the non-metric traits for the P⁴, M¹ and M³, “rather than being *H. sapiens*-like [...] have trait express that are ambiguous”. We struggle to understand where we disagree here, as our study explicitly stated that some of the Axlor teeth have features that are observed in Neandertals in high frequencies (e.g., the bifurcated essential crest of both the lingual and buccal cusps in the P⁴ at the EDJ level). González-Urquijo et al. (2021: 553) also consider that “most of the traits do not clearly distinguish Neanderthals and Upper Paleolithic *H. sapiens*”. For that exact reason, we combined qualitative and quantitative methods for the taxonomic assessment of the Axlor teeth, as opposed to the qualitative-only evaluation performed by González-Urquijo and colleagues.
González-Urquijo et al. (2021: 553) disagree with one of our assessments of the M¹ characters as they consider that the hypocone is slightly larger than the metacone at the occlusal enamel surface (OES) and the enamel-dentine junction (EDJ). However, they do not provide an image showing how they measured these areas. Indeed, our original study did not include a formal metric comparison of the hypocone and the metacone of the M¹ because the high degree of wear of this molar makes these measurements tentative. Therefore, we simply stated that both the hypocone and the metacone of Axlor show a grade 4 of expression based on the ASUDAS scoring system (Turner, Nichol, & Scott, 1991; Gómez-Olivencia et al., 2020: Table 4).

González-Urquijo et al. (2021: 553) enumerate a series of methodological issues related to the analysis of the Axlor's M¹ that were explicitly addressed or that indicate their lack of understanding of the methods we used in our study. Firstly, they consider “curious that a quantitative assessment of this tooth was even undertaken since Gómez-Robles et al. explicitly excluded severely worn teeth”. Our study explicitly discussed the limitations of identifying cusp tips in worn molars, which is why we performed the geometric morphometric analysis of the M¹ from Axlor twice: once using both the cusp tips and the outline, and once using only the outline. Discriminant analyses indicated a probability of around 99% for this molar to belong to *Homo sapiens* in both cases.

González-Urquijo et al. (2021) state that we did not indicate whether the outline was corrected. The outline of the M¹ was indeed corrected as it is the standard procedure in geometric morphometric analyses of molar shape (Gómez-Robles et al., 2007). We clearly stated that we used “the Neandertal and modern human samples used in Gómez-Robles et al. (2007), Gómez-Robles, Bermúdez de Castro, Martinón-Torres, Prado-Simón, and Arsuaga (2012), and Gómez-Robles, Martinón-Torres, Bermúdez de Castro, Prado-Simón, and Arsuaga (2011).” (Gómez-Olivencia et al., 2020: 479). While not explicitly stated, this was meant to imply that the same methodology was used: “When mesial and/or distal borders of the teeth were affected by light interproximal wear, original borders were estimated by reference to overall crown shape and the buccolingual extent of
the wear facets, following Wood and Engleman (1988) and Bailey (2004)” (Gómez-Robles et al., 2007: 275-276).

Additionally, González-Urquijo et al. (2021) estimate that between 30% and 37% (between 9 and 11) of the semilandmarks are missing in Axlor's M¹ (see their Figure 1, where they provide a new outline for Axlor's M¹). This outline assumes that landmarks 22-28 are affected by wear, and thus the suggested outline enlarges both the metacone and, especially, the hypocone. While we fully agree with González-Urquijo and colleagues on the correction performed on the mesial outline, which is similar to the one we performed to carry out our analysis, their distal correction is clearly incorrect. An inspection of the Axlor's M¹ 3D model (which is freely available in Figshare; see the Data Availability Statement below and in Gómez-Olivencia et al., 2020) clearly reveals that the surface of the inter-proximal facet is very limited and does not extend to the hypocone semilandmarks (Figure 1). Therefore, the outline correction illustrated by González-Urquijo et al. on the distal aspect of the molar substantially exceeds the actual interproximal wear of this molar, making it look more Neandertal.

González-Urquijo et al. (2021: 554) state that “the absence of clear divisions between cusps complicates accurately positioning the centroid that is used to place the semilandmarks.” Firstly, the location of the centroid depends on the location of the cusp tips, not on the presence of “clear divisions between cusps”. As stated above, the degree of wear of this molar does interfere with the accurate location of the four landmarks that the centroid position is based on. However, the specific location of each semilandmark on the outline, which does depend on the calculated centroid, is modified through a sliding algorithm that, again, is a standard step of geometric morphometric analyses (Bookstein, 1996, 1997; Bookstein, Sampson, Connor, & Streissguth, 2002; Gunz, Mitteroecker, & Bookstein, 2005). Hence, any ambiguity in the original positioning of the semilandmarks is ameliorated by the sliding procedure.
[INSERT FIGURE 1 HERE]

Our geometric morphometric analysis revealed that: a) Axlor's M¹ falls closer to the modern human consensus shape than to the Neandertal consensus shape; and b) the M¹ discriminant analysis provided a very high probability to belong to a modern human, while P⁴ and M³ were not conclusive (Gómez-Olivencia et al., 2020). However, it is widely accepted that upper first molars are one of the most diagnostic teeth when distinguishing between Neandertals and modern humans (e.g., Gómez-Robles et al., 2007). When considering PC1 and PC2, the Axlor M1 falls closer to both recent and fossil *Homo sapiens* centroids than to the Neandertal distribution centroid. Overlap is minimal in this plot and only one Neandertal individual from our Neandertal sample (the one from Pech de l'Azé) falls close to Axlor and the recent human centroid (Gómez-Olivencia et al., 2020: Figure 6).

It is also important to note that the discriminant analyses in Gómez-Olivencia et al. (2020) were based on the first 10 PCs not just on the two first PCs shown in the figures. Although not reported in our original study, we include here the cross-validated percentages of correct classification: 93.3% overall, with 73.3% of Neandertals and 100% of modern humans correctly classified. Additionally, when the form space is analyzed, the Axlor M¹ falls outside the range of variation of the Neandertal sample (Gómez-Olivencia et al., 2020).

With respect to the other teeth, we agree with González-Urquijo et al. (2021) that the well-developed mesial ridge and lingual tubercle present in the Axlor canine are traits present in Neandertals in high percentages. Interestingly, they mention the presence of one UP canine (out of 10) with a well-developed mesial ridge, but then question its taxonomic attribution. Our revision of published UP specimens reveals that a tuberculum dentale is also present in other UP specimens (Sunghir 2, Sunghir 3, Mladeč 9; Frayer, Jelínek, Oliva, & Wolpoff, 2006; Trinkaus, Buzhilova, Mednikova, & Dobrovolskaya, 2014). Moreover, Mladeč 9 also presents a well-developed mesial
ridge (although smaller than the distal one), which is attached to the tuberculum dentale as in the canine from Axlor (see Frayer et al., 2006: Figure 19 vs Basabe, 1973: Figure 7).

González-Urquijo et al. (2021: 553) disagree with our assessment of two additional traits and state that the “lingual essential crest of the P⁴ that Gómez-Olivencia et al. scored as absent is clearly present at both the OES and the EDJ”. However, we clearly stated that the lingual essential crest is present at the EDJ with a score of 2. This crest was scored as “NO” at the OES level, which means “non observable” (although we failed to spell this out in the legend of our table). Unlike González-Urquijo and colleagues, we considered that the assessment of this trait at the OES level is too tentative given the substantial degree of wear present in this tooth. In our table, those traits that are absent are clearly indicated by “0 (absent)” (Gómez-Olivencia et al., 2020: Table 3). While we admit our error for not spelling out the abbreviation, this does not make these teeth any more Neandertal.

In the case of the hypocone in the M³, we considered that this as an additional cusplet/tubercle, since it is not clearly visible in the original OES (and thus our scoring as 0). As the scoring of other qualitative traits, our assessment (as González-Urquijo and colleagues') bears certain degree of subjectivity, which is why a quantitative assessment is always preferred. In any case, even if the presence of a hypocone in the M³ were accepted, this trait would still be unable to distinguish between Neandertals and modern humans (see Martinón-Torres et al., 2012).

## 4 Stratigraphic study

In his field notes and in the published report of Axlor excavations, J. M. de Barandiarán describes quite clearly the context of the human remains: i) The site of Axlor was severely affected during the end of the XIX century and or the beginning of the XX century, resulting in the destruction of a large part of the site, mostly the upper levels, situated in the right part of the site (Barandiarán, 1980); ii) The human remains under discussion, according to his field notes, were found in the limit of the preserved area, immediately below the mixed sediment that covered the
destructed area, and they were the first archaeological remains noted in square 13F; iii) The remains were found in a loose sediment that contrasts with the encrusted sediments excavated beside squares 13E and 13F by J. González Urquijo between 2000 and 2008 (González Urquijo, 2009; González Urquijo et al., 2003).

In their reply, González-Urquijo et al. (2021) do not present any new information that contradicts the description made by J. M. de Barandiarán or by González-Urquijo’s own team in previous reports and publications (Barandiarán, 1980; González Urquijo et al., 2006; Rios Garaizar et al., 2003). Moreover, some of the interpretations and data presented by González-Urquijo et al. (2021) suffer from important omissions:

i) The radiocarbon date table published by González-Urquijo et al. (2021) does not include the spatial information of the samples, nor the information about methods, pretreatment and quality of the samples. Additionally, they omit two published dates from level F made by themselves (Rios-Garaizar, 2017). One of these dates yielded a result of 33,310±360 (sample Beta-225485) which is extremely important for addressing possible disturbances at the site (Rios-Garaizar, 2012).

González-Urquijo et al. (2021) reassign one sample (sample Beta-144262) traditionally published as belonging to level D (González Urquijo et al., 2006) to level B without further explanation. Finally, they omit the radiocarbon dates from Axlor published by Marín-Arroyo et al. (2018) (see Table 1).

[INSERT TABLE 1 HERE]

ii) González-Urquijo et al. (2021) base their argument on the poor preservation of the Upper Paleolithic (UP) faunal remains found in F8 and F9, but they neglect to mention that a human tooth was found in this level in 2008 (González Urquijo, 2009). Furthermore, González-Urquijo et al. (2021) propose a geometry for the UP level omitting that original extension of this level is unknown for two reasons. First, due to the aforementioned partial destruction of the site; and second, due to
the excavation of J. M. de Barandiarán who barely recovered, accordingly with the available records, 13 lithic artifacts from level I and 8 lithic artifacts from level II.

iii) The currently available information about the stratigraphic context adjacent to the place where the human remains under discussion were found indicates that the stratigraphic sequence is very difficult to read, that the sediment is encrusted (González Urquijo et al., 2006), and that no new human remains have been recovered there (González Urquijo et al., 2003).

## 5 Discussion and conclusions

Here we reiterate that a Neandertal classification for the teeth found in Axlor in 1967 is unlikely. Firstly, the supposedly Neandertal traits discussed by González-Urquijo and colleagues (2021) are ambiguous, unclear or based on an erroneous assessment of the teeth. Second, we show that González-Urquijo et al. (2021) do not present any new information that contradicts the stratigraphic description made by J. M. de Barandiarán or by his team in previous reports and publications, and that they omit important information regarding the archaeological context of the human remains found in 1967.

As stated in our original publication, the body of evidence points to a modern human classification for these teeth, with very high probabilities in one of the most informative teeth, the M¹. Though species-specific morphologies exist, dental size and shape are variable in both species and unable to unquestionably discriminate between them, particularly for specimens that do not show the most extreme species-specific traits. In addition, the Middle to Upper Paleolithic transition entailed a complex scenario that included both cultural changes and population replacement. Recent developments in ancient DNA analyses have complicated the picture, with evidence of admixture between Neandertals and modern humans (Fu et al., 2015). Fossil remains with ambiguous Neandertal and modern human traits may represent the anatomical evidence of those admixture events (see Compton et al., 2021), although molecular analyses are required to confirm this point.
In sum, the teeth found in Axlor in 1967 show a few features which typically appear in Neandertals in high frequencies, but which are also present in *H. sapiens*. However, most traits, including the quantitative morphometric analysis of the M¹ show *H. sapiens* affinities. Therefore, we favor this taxonomic classification. Genetic analyses and direct dating, however, are the only way forward to unequivocally clarify their chronology and further inform discussions about their ancestry.

## ACKNOWLEDGMENTS

This research has received support from the Spanish Ministerio de Ciencia e Innovación (proyecto PGC2018-093925-B-C33, MCI/AEI/FEDER, UE), Research Group IT1418-19 from the Eusko Jaurlaritza-Gobierno Vasco, and N. Ergal Foundation. AGO was supported by Ramón y Cajal fellowship (RYC-2017-22558). NS was supported by DEATHREVOL project that has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (Grant agreement No. 949330) and by Ramón y Cajal fellowship (RYC2020-029656-I). DLO was supported by an MSC Actions Individual Fellowship (Project N°895713). IA-C acknowledges the support by the University of the Basque Country UPV/EHU grant GIU19/027. We would like to thank the Editor, the AE, and the reviewers for very useful comments that have helped to improve this paper.

## Data Availability Statement

The original micro-ct scans, the derived segmentation files, and 3D volumes are available in figshare at https://doi.org/10.6084/m9 figshare.10308272.

## REFERENCES

Bailey, S. E. (2004). A morphometric analysis of maxillary molar crowns of Middle-Late Pleistocene hominins. *Journal of Human Evolution*, 47(3), 183-198. doi:10.1016/j.jhevol.2004.07.001
Barandiarán, J. M. (1980). Excavaciones en Axlor. 1967-1974. In J. M. Barandiarán (Ed.), *Obras Completas de José Miguel de Barandiarán Tomo XVII* (pp. 127-384). Bilbao: La Gran Enciclopedia Vasca.

Basabe, J. M. (1973). Dientes humanos del Musteriense de Axlor (Dima. Vizcaya). *Trabajos de Antropología, 16*, 187-207.

Basabe, J. M. (1982). Restos fósiles humanos de la región Vasco-Cantábrica. *Cuadernos de Sección. Antropología-Etnografía Prehistoria-Arqueología, 1*, 67-84.

Bookstein, F. L. (1996). Applying landmark methods to biological outline data. In K. V. Mardia, C. A. Gill & I. L. Dryden (Eds.), *Image Fusion and Shape Variability Techniques*. Leeds: Leeds University Press.

Bookstein, F. L. (1997). Landmark methods for forms without landmarks: morphometrics of group differences in outline shape. *Medical Image Analysis, 1*(3), 225-243. doi:10.1016/S1361-8415(97)85012-8

Bookstein, F. L., Sampson, P. D., Connor, P. D., & Streissguth, A. (2002). Midline corpus callosum is a neuroanatomical focus of fetal alcohol damage. *The Anatomical Record, 269*.

Compton, T., Skinner, M. M., Humphrey, L., Pope, M., Bates, M., Davies, T. W., ... Stringer, C. (2021). The morphology of the Late Pleistocene hominin remains from the site of La Cotte de St Brelade, Jersey (Channel Islands). *Journal of Human Evolution, 152*, 102939. doi:10.1016/j.jhevol.2020.102939

Frayer, D. W., Jelínek, J., Oliva, M., & Wolpoff, M. H. (2006). Aurignacian female crania and teeth from the Mladeč Caves, Moravia, Czech Republic. In M. Teschler-Nicola (Ed.), *Early Modern Humans at the Moravian Gate. The Mladeč Caves and their remains* (pp. 185-272). Wien: Springer.

Fu, Q., Hajdinjak, M., Moldovan, O. T., Constantin, S., Mallick, S., Skoglund, P., ... Pääbo, S. (2015). An early modern human from Romania with a recent Neanderthal ancestor. *Nature, 524*, 216-219. doi:10.1038/nature14558

Garralda, M. D., Maureille, B., Le Cabec, A., Oxilia, G., Benazzi, S., Skinner, M. M., ... Vandermeersch, B. (2020). The Neanderthal teeth from Marillac (Charente, Southwestern France): Morphology, comparisons and paleobiology. *Journal of Human Evolution, 138*, 102683. doi:10.1016/j.jhevol.2019.102683

Gómez-Olivencia, A., López-Onaindia, D., Sala, N., Balzeau, A., Pantoja-Pérez, A., Arganda-Carreras, I., ... Gómez-Robles, A. (2020). The human remains from Axlor (Dima, Biscay, northern Iberian Peninsula). *American Journal of Physical Anthropology, 172*(3), 475-491. doi:10.1002/ajpa.23989

Gómez-Robles, A., Bermúdez de Castro, J. M., Martinón-Torres, M., Prado-Simón, L., & Arsuaga, J. L. (2012). A geometric morphometric analysis of hominin upper second and third molars, with particular emphasis on European Pleistocene populations. *Journal of Human Evolution, 63*(3), 512-526. doi: http://dx.doi.org/10.1016/j.jhevol.2012.06.002

Gómez-Robles, A., Martinón-Torres, M., Bermúdez de Castro, J. M., Margvelashvili, A., Bastir, M., Arsuaga, J. L., ... Martínez, L. M. (2007). A geometric morphometric analysis of hominin upper first molar shape. *Journal of Human Evolution, 53*, 272-285. doi:10.1016/j.jhevol.2007.02.002

Gómez-Robles, A., Martinón-Torres, M., Bermúdez de Castro, J. M., Prado-Simón, L., & Arsuaga, J. L. (2011). A geometric morphometric analysis of hominin upper premolars. Shape variation and morphological integration. *Journal of Human Evolution, 61*(6), 688-702. doi:10.1016/j.jhevol.2011.09.004

González Urquijo, J. (2009). Axlor. IX Campaña. *Arkeoikuska, 08*, 245-248.

González Urquijo, J., & Ibáñez Estévez, J. J. (2002). Abrigo de Axlor (Dima). *Arkeoikuska, 2001*, 90-93.

González Urquijo, J., Ibáñez Estévez, J. J., & Ríos Garaizar, J. (2003). *Excavación en el yacimiento arqueológico de Axlor (Dima, Bizkaia). Un estudio arqueológico y antropológico de la transición entre el Paleolítico Medio y el Superior. La extinción de los neandertales y la aparición de los humanos modernos en el País Vasco.*

González Urquijo, J., Ibáñez Estévez, J. J., Ríos Garaizar, J., & Bourguignon, L. (2006). Aportes de las nuevas excavaciones en Axlor sobre el final del Paleolítico Medio. In V. Cabrera Valdés, F. Bernaldo de Quirós Guidotti & J. M. Maíllo Fernández (Eds.), *En el centenario de la cueva de El*
*Castillo: el ocaso de los neandertales* (pp. 269-291). Santander: Universidad Nacional de Educación a Distancia - UNED.

González-Urquijo, J., Bailey, S. E., & Lazuen, T. (2021). Axlor's level IV human remains are convincingly Neanderthals: A reply to Gómez-Olivencia et al. *American Journal of Physical Anthropology*, *176*(4), 553-558. doi:10.1002/ajpa.24252

Gunz, P., Mitteroecker, P., & Bookstein, F. L. (2005). Semilandmarks in three dimensions. In D. Slice (Ed.), *Modern morphometrics in Physical Anthropology* (pp. 73-98). New York: Kluwer Academic/Plenum Publishers.

Lazuen Fernández, T., & González-Urquijo, J. (2019-2020). El estudio de las formas de vida de las sociedades neandertales en el yacimiento de Axlor (Dima, Bizkaia): las excavaciones de J.M. Barandiaran y el proyecto del siglo XXI. *Anuario de Eusko Folklore Urtekaria*, *54*, 47-69.

Marín-Arroyo, A. B., Rios-Garaizar, J., Straus, L. G., Jones, J. R., de la Rasilla, M., González Morales, M. R., ... Ocio, D. (2018). Chronological reassessment of the Middle to Upper Paleolithic transition and Early Upper Paleolithic cultures in Cantabrian Spain. *Plos one*, *13*(4), e0194708. doi:10.1371/journal.pone.0194708

Martinón-Torres, M., Bermúdez de Castro, J. M., Gómez-Robles, A., Prado-Simón, L., & Arsuaga, J. L. (2012). Morphological description and comparison of the dental remains from Atapuerca-Sima de los Huesos site (Spain). *Journal of Human Evolution*, *62*(1), 7-58.

Rios Garaizar, J., González Urquijo, J. E., & Ibáñez Estévez, J. J. (2003). La excavación en Axlor. Las formas de vida de los últimos neandertales. *Boletín de la SEDECK*, *5*, 62-83.

Rios-Garaizar, J. (2012). *Industria lítica y sociedad en la transición del Paleolítico Medio al Superior en torno al Golfo de Bizkaia*. Santander: PUbliCan-Ediciones de la Universidad de Cantabria.

Rios-Garaizar, J., 2017. A new chronological and technological synthesis for Late Middle Paleolithic of the Eastern Cantabrian Region. *Quaternary International*, *433*, 50-63.

Rostro Carmona, J. (2013). Estudio comparado de las piezas dentales de *Homo neanderthalensis* del yacimiento Musteriense de Axlor (Dima, Vizcaya). *CKQ Estudios de Cuaternario/Kuaternario Ikasketak/Quaternary Studies*, *3*, 91-100.

Trinkaus, E., Buzhilova, A. P., Mednikova, M. B., & Dobrovolskaya, M. V. (2014). *The People of Sunghir*. *Burials, Bodies, and Behavior in the Earlier Upper Paleolithic*. Oxford: Oxford University Press.

Turner II, C. G., Nichol, C. R., & Scott, G. R. (1991). Scoring procedures for key morphological traits of the permanent dentition: the Arizona State University dental anthropology system. In M. Kelley & C. Larsen (Eds.), *Advances in Dental Anthropology* (pp. 13-31). New York: Wiley-Liss.

Wood, B. A., & Engleman, C. A. (1988). Analysis of the dental morphology of Plio-Pleistocene hominids. *V. Maxillary postcanine tooth morphology*. *Journal of Anatomy*, *161*, 1-35.
FIGURE LEGENDS

Figure 1. A) Semilandmarks proposed by González-Urquijo et al. (2021) as an accurate correction of Axlor's M¹ outline; B) Corrected outline used by Gómez-Olivencia et al. (2020) in their original assessment. C and D) Occlusal-distal showing that the extension of the distal facet (marked in red in D) does not affect the occlusal outline. E) Outline of a M¹ from Krapina (Krapina 100) showing the bulging hypocone, typical of Neandertal populations (and also of European Middle Pleistocene populations) (Bailey, 2004; Gómez-Robles et al., 2007; Martinón-Torres, Bermúdez de Castro, Gómez-Robles, Prado-Simón, & Arsuaga, 2012).
<table><caption>Table 1
Available radiocarbon dates for Axlor late Middle Paleolithic levels B, D and F.</caption><thead><tr><th>Level*</th><th>Sample reference</th><th>Lab Code</th><th>Date (BP)</th><th>Method</th><th>Material</th><th>Taxon, anatomical part</th><th>%C</th><th>%N</th><th>C:N</th><th>δ<sup>13</sup>C</th><th>δ<sup>15</sup>N</th><th>References</th></tr></thead><tbody><tr><td>B**</td><td>na</td><td>Beta-144262</td><td>42,010±1280</td><td>AMS</td><td>Bone</td><td>Non determ.</td><td></td><td></td><td></td><td></td><td></td><td>González Urquijo &amp; Ibañez Estévez, 2002; González Urquijo et al., 2021</td></tr><tr><td>B</td><td>na</td><td>Beta-203108</td><td>42,720±900</td><td>AMS</td><td>Bone</td><td>Bos/Bison; tibia</td><td></td><td></td><td></td><td></td><td></td><td>González Urquijo et al., 2021</td></tr><tr><td>D</td><td>na</td><td>Beta-203107</td><td>44,920±1950</td><td>AMS</td><td>Bone</td><td>Bos/Bison; axis</td><td></td><td></td><td></td><td></td><td></td><td>González Urquijo et al., 2021</td></tr><tr><td>D</td><td>na</td><td>Beta-225486</td><td>>43,000</td><td>AMS</td><td>Bone</td><td>Cervus; metapodial</td><td></td><td></td><td></td><td></td><td></td><td>Rios-Garaizar, 2012; González Urquijo et al., 2021</td></tr><tr><td>F</td><td>na</td><td>Beta-225478</td><td>>47,500</td><td>AMS</td><td>Bone</td><td>Cervus; metapodial</td><td></td><td></td><td></td><td></td><td></td><td>Rios-Garaizar, 2012</td></tr><tr><td>F</td><td>na</td><td>Beta-225485</td><td>33,310±360</td><td>AMS</td><td>Bone</td><td>Cervus; metapodial</td><td></td><td></td><td></td><td></td><td></td><td>Rios-Garaizar, 2012</td></tr><tr><td>IV</td><td>AX.11C.290.149</td><td>OxA-32428</td><td>>49,300</td><td>UF-AMS</td><td>Bone</td><td>Cervus elaphus; phalanx 2</td><td>42.3</td><td>3.5</td><td>3.3</td><td>-19.8</td><td>3.5</td><td>Marín-Arroyo et al., 2018</td></tr><tr><td>IV</td><td>AX.11C.300.178</td><td>OxA-32429</td><td>>49,900</td><td>UF-AMS</td><td>Bone</td><td>Cervus elaphus; carpal</td><td>43.0</td><td>6.3</td><td>3.3</td><td>-19.2</td><td>6.3</td><td>Marín-Arroyo et al., 2018</td></tr></tbody></table>

* Level attribution with letters (B, D and F) correspond with 2000-2008 excavations; Roman ordinals with 1967-1974 excavations.

** In the original publication this sample is attributed to level D, in the recent publication to level B.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60

<figure><img src="image_4.png" /><figcaption>Figure 1. A) Semilandmarks proposed by González-Urquijo et al. (2021) as an accurate correction of Axlor's M1 outline; B) Corrected outline used by Gómez-Olivencia et al. (2020) in their original assessment. C and D) Occlusal-distal showing that the extension of the distal facet (marked in red in D) does not affect the occlusal outline. E) Outline of a M1 from Krapina (Krapina 100) showing the bulging hypocone, typical of Neandertal populations (and also of European Middle Pleistocene populations) (Bailey, 2004; Gómez-Robles et al., 2007; Martinón-Torres, Bermúdez de Castro, Gómez-Robles, Prado-Simón, & Arsuaga, 2012).</figcaption></figure>