# Modelling Neanderthal Extinction — *abridged version*

Louise Ouvrard and Anna Degioanni

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URL: https://journals.openedition.org/pm/3385

DOI: 10.4000/pm.3385

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**This article is a translation of:**

Modélisation de l'extinction de Néandertal - URL : https://journals.openedition.org/pm/3312 [fr]

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Louise Ouvrard and Anna Degioanni, "Modelling Neanderthal Extinction — *abridged version*", *Préhistoire Méditerranéennes* [Online], 9.1 | 2021, Online since 17 December 2021, connection on 23 November 2024. URL: http://journals.openedition.org/pm/3385; DOI: https://doi.org/10.4000/pm.3385

This text was automatically generated on November 23, 2024.

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The text only may be used under licence CC BY 4.0. All other elements (illustrations, imported files) are
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# Modelling Neanderthal Extinction —
*abridged version*

Louise Ouvrard and Anna Degioanni

## EDITOR'S NOTE

This article is not quite a translation but rather a long summary of the French article: Modélisation de l'extinction de Néandertal

Received 13.07.2021; Received in revised form 07.12.2021; 08.12.2021; Online 17-12-2021

English abstract and abridged version written by the authors, revised and corrected by Karina Gerdau.

1. Neanderthals, throughout their long existence, occupied the regions around the Mediterranean until their disappearance between 50,000 BP and 35,000 BP (Timmermann, 2020). Since this rather rapid event coincides with the arrival of Anatomically Modern Humans (AMH) in Europe at around 46,000 BP (Hublin et al., 2020), researchers consider that AMH played an important role in the decline of Neanderthals, who were “exterminated” by the newcomers through direct or indirect competition (Tattersall and Schwartz 1999). Nonetheless, Neanderthals’ archaeological record is not sufficiently different to that of AMH and does not help explain their population decline in terms of observable inferiority (Villa and Roebroeks 2014).

2. Neanderthals’ demography was modelled over the 15,000 years prior to their extinction in an attempt to understand how it “functioned”, as modelling can help explain a complex phenomenon – here, the extinction of a species as a set of simple mathematical equations. Ecological models of competition, studied and mathematically demonstrated by Vito Volterra (1926, 1931) and Alfred J. Lotka (1925, 1932), and analysed empirically by Georgy Gause (1934), were adapted, in particular, the Flores model (1998).

3. Four different scenarios (A, B, C and D) were tested to analyse Neanderthal population dynamics over the last 15,000 years of their existence. The values used were taken from
the literature (Tables 1 and 2). For each of the scenarios, the two extreme values of Neanderthal population size were considered: 5,000 individuals and 70,000 individuals.

<table><caption>Table 1: Presentation of the parameters for each scenario, the origin of the values is presented in Table 2.</caption><thead><tr><th>Scenario</th><th></th><th>Population size</th><th>Fertility rate</th><th>Mortality rate</th></tr></thead><tbody><tr><td rowspan="2">Neanderthal alone</td><td rowspan="2">Scenario A</td><td>1 5 000</td><td>0,141</td><td>0,4029</td></tr><tr><td>2 70 000</td><td>0,141</td><td>0,4029</td></tr><tr><td rowspan="2">Neanderthal + migrations</td><td rowspan="2">Scenario B</td><td>1 5 000</td><td>0,141</td><td>0,4029</td></tr><tr><td>2 70 000</td><td>0,141</td><td>0,4029</td></tr><tr><td rowspan="2">Néandertal + migrations + crossings</td><td rowspan="2">Scenario C</td><td>1 5 000</td><td>0,141</td><td>0,4029</td></tr><tr><td>2 70 000</td><td>0,141</td><td>0,4029</td></tr><tr><td rowspan="4">For which fertility and mortality values does Neanderthal disappear in 15,000 years?</td><td rowspan="4">Scenario D</td><td>1 5 000</td><td>0,001</td><td>0,3342</td></tr><tr><td>2 70 000</td><td>0,001</td><td>4,6675</td></tr><tr><td>3 5 000</td><td>0,141</td><td>0,4742</td></tr><tr><td>4 70 000</td><td>0,141</td><td>4,8075</td></tr></tbody></table>

<table><thead><tr><th>Parameter</th><th>Value</th><th>Source</th></tr></thead><tbody><tr><td>Neanderthal population (N)</td><td>Between 5,000 and 70,000</td><td>Bocquet-Appel & Degioanni 2013</td></tr><tr><td>Date of Neanderthal extinction</td><td>Between 50,000 and 35,000 BP</td><td>Timmermann 2020</td></tr><tr><td>Period during which HAM and Neanderthal coexist</td><td>From 50,000 to 35,000 BP</td><td>Villanea & Schraiber 2019</td></tr><tr><td>Neanderthal fertility rate (Fn)</td><td>Between 0,1415 et 0,13</td><td>Degioanni et al. 2019</td></tr><tr><td>HAM fertility rate (Fc)</td><td>0,403</td><td>Bocquet-Appel 2008</td></tr><tr><td>Mortality rates of the HAM (Dc) and Neanderthal (Dn)</td><td>0,4029</td><td>Bocquet-Appel 2008</td></tr><tr><td>Interbreeding frequency</td><td>Once every 37 years</td><td>Currat & Excoffier 2011</td></tr><tr><td>Similarity(ies) parameter</td><td>0,998</td><td>Adapted from the equation of Flores 1998</td></tr></tbody></table>
<table><caption>Table 2: Parameters used, values assigned and sources.</caption><tr><td>Migrations</td><td>1 group/iteration</td><td>Kolodny & Feldman 2017</td></tr></table>

4

In scenario A, Neanderthals are the only occupants of their territory during the last 15,000 years of their existence. In scenario B, Neanderthals are still the only occupants of their territory, but recurrent migrations of AMH from Africa are considered (the number of AMH immigrants is randomly drawn between 0 and 200, if this number is between 10 and 21 then a group of AMH is allowed to migrate). Scenario C allows for admixture between the two populations. Indeed, paleogenetic analyses demonstrate that a fraction of the genome of present-day non-African humans is inherited from Neanderthals (Green et al. 2010). Upon their arrival on Eurasian territory, AMH interbreed with Neanderthals and give rise to fertile and viable individuals. In this scenario, “hybrid” births are classed as AMH and the frequency of this admixture is very low, with one successful hybridisation every 37 years (Currat and Excoffier 2011). Tests of the first three scenarios, A, B and C (fig. 1), using the values proposed in the literature, show that population dynamics are such that Neanderthals do not disappear. There are only two possibilities: either the model is “unlikely” or the proposed values are incorrect.

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

1. Population dynamics of Neanderthals (red) and HAM (blue) over 15,000 years.

The solid line illustrates scenario A2: Neanderthals are alone on the Euro-Asian territory;
The dotted line illustrates scenario B2: small groups (less than 20 individuals) of HAM immigrate;
The small line illustrates scenario C2: between Neanderthals and HAM there is interbreeding and the newborns integrate the HAM.

5

For scenario D, instead of the data proposed in the literature, different values for mortality and fertility of Neanderthals were tested, and the values retained were exclusively those that allowed for their disappearance (i.e., population size equal to 0) after 15,000 years. For a population of 70,000 Neanderthals to disappear in 15,000 years,
the fertility value must vary between 0.001 and 1.141, and the mortality value between 4.8075 and 4.6675 (fig. 2). For a population of 5,000 Neanderthals to become extinct in 15,000 years, the fertility value must fall between 0.07 and 1.141, and the mortality value between 0.4029 and 0.4742.

6. None of the scenarios proposed explain the extinction of Neanderthals as the result of competition between two species with almost similar needs in the same environment. For the whole population of individuals with Neanderthal traits to disappear, the values of the main demographic parameters (fertility and mortality rates) must therefore change considerably from the values selected for the implementation of our model.

<figure><img src="image_4.png" /></figure>

## 2. Population dynamics of Neanderthals (in red) and HAM (in blue).

The dotted line illustrates scenario D2: very low fertility value of Neanderthals; The solid line illustrates scenario D4: very high Neanderthal mortality value.

7. Unfortunately, these results remain unsupported by archaeological data. It is possible that some parameters have not been considered and that this model is too “simplistic. Indeed, it is not spatially explicit. Consequently, the results reflect the general demographic dynamics of a population whose territory is not delimited. Moreover, Neanderthals were not a single population but lived in small groups, accordingly the values of the main parameters may vary from group to group. Finally, in this analysis, the age structure of the population was not considered and a single fertility and mortality rate was used for all age categories. Previous research has shown (Degioanni et al 2019) that a simple reduction in the fertility rate of the youngest females can have a very important impact on population dynamics.

# Supplementary data

8. MeN-R-Script is a complementary data from the article Louise Ouvrard, Anna Degioanni "Modelling the extinction of the Neanderthal", *Préhistoires méditerranéennes*
vol. 9.1|2021.

This script was written and used by Louise Ouvrard for her Master 2 project (Aix-
Marseille Univ, MMSH, LAMPEA), "Extinction of the Neanderthal: the impact of
crossbreeding and competition with anatomically modern humans", academic year
2020/2021.

Name

9 MeN-R-Script

R-Script for a Modelling Neanderthal Extinction

Repository location

10 Nakala [dataset]. Interface for depositing and managing data from Huma-Num Research Infrastructure.

Permanent link

11 https://doi.org/10.34847/nkl.fce42542

DOI: 10.34847/nkl.fce42542

creation and deposit date

12 V1 created on 2021/12/09

V1 published on 2021/12/17

Dataset Format

13 .txt

Software version

14 RStudio Team 2020

Package used: svDialogs

License

15 Etalab Open License 2.0

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## ABSTRACTS

Neanderthals, throughout their existence, occupied a vast territory between Europe and Asia. Their rather rapid extinction coincided with the arrival of Anatomically Modern Humans (AMH) in Europe. Although the causes of Neanderthal extinction have yet to be established, there are several hypotheses, researchers favouring the one in which AMH competed for resources with Neanderthals, who were at a disadvantage. To understand Neanderthal demography, this paper presents different models for the last 15,000 years preceding their disappearance. Different scenarios were tested using data available from the scientific literature. The results indicate that Neanderthals should have survived, and therefore, that the scenarios modelled are “unlikely” since we know that they did not. Consequently, either the scenarios modelled have not been correctly constructed or the values used are not close enough to reality. Accordingly, the values of the demographic parameters that could have determined the extinction of the Neanderthals were identified. For Neanderthals to disappear in 15,000 years, their fertility would have had to decrease and their mortality would have had to increase sharply. The arrival of AMH does not seem to be the only factor capable of influencing Neanderthal population dynamics.

Les Néandertaliens, au cours de leur existence, occupent un vaste territoire compris entre l'Europe et l'Asie. Leur extinction plutôt rapide coïncide avec l'arrivée des Hommes anatomiquement modernes (HAM) en Europe. Même si les causes de l'extinction des Néandertaliens ne sont pas aujourd'hui établies, un grand nombre d'hypothèses existent, celle privilégiée est l'entrée en compétition pour les ressources des HAM avec les Néandertaliens, ces derniers étant désavantagés face aux nouveaux arrivants.

Nous utilisons la modélisation afin de comprendre le « fonctionnement » de la démographie des Néandertaliens au cours des 15 000 ans qui précèdent leur extinction.

Nous proposons différents scénarios, testés en utilisant les données issues de la littérature scientifique.

Les résultats nous indiquent que Néandertal aurait survécu, et donc que ces scénarios ne sont pas « vraisemblables ». Dès lors, soit les scénarios n'ont pas été correctement construits, soit les valeurs utilisées ne sont pas assez proches de la réalité. Nous avons donc choisi d'identifier les valeurs des paramètres démographiques (fertilité et mortalité) qui auraient pu déterminer l'extinction des Néandertaliens. Nous nous apercevons que pour que Néandertal disparaisse en 15 000 ans, il est nécessaire que sa fertilité baisse et que sa mortalité augmente fortement. L'arrivée de l'HAM ne semble pas être le seul facteur capable d'influer sur la dynamique des Néandertaliens.

## INDEX

**Keywords:** Neanderthals, extinction, modelling, admixture, Modern Humans, paleodemography

**Mots-clés:** Néandertal, extinction, modélisation, croisement, Homme moderne, paléodémographie
# AUTHORS

## LOUISE OUVRARD

Aix Marseille Univ, CNRS, Minist Culture, LAMPEA, Aix-en-Provence, France, 5 rue du Château de l'Horloge, 13094, Aix-en-Provence, Cedex 2, France

## ANNA DEGIOANNI

Aix Marseille Univ, CNRS, Minist Culture, LAMPEA, Aix-en-Provence, France, 5 rue du Château de l'Horloge, 13094, Aix-en-Provence, Cedex 2, France - anna.degioanni@univ-amu.fr