Abstract
The replacement of Neanderthals by Anatomically Modern Humans has typically been attributed to environmental pressure or a superiority of modern humans with respect to competition for resources. Here we present two independent models that suggest that no such heatedly debated factors might be needed to account for the demise of Neanderthals. Starting from the observation that Neanderthal populations already were small before the arrival of modern humans, the models implement three factors that conservation biology identifies as critical for a small population’s persistence, namely inbreeding, Allee effects and stochasticity. Our results indicate that the disappearance of Neanderthals might have resided in the smallness of their population(s) alone: even if they had been identical to modern humans in their cognitive, social and cultural traits, and even in the absence of inter-specific competition, Neanderthals faced a considerable risk of extinction. Furthermore, we suggest that if modern humans contributed to the demise of Neanderthals, that contribution might have had nothing to do with resource competition, but rather with how the incoming populations geographically restructured the resident populations, in a way that reinforced Allee effects, and the effects of inbreeding and stochasticity.
Highlights
A long-standing enigma in palaeoanthropology is the demise of Neanderthals approximately 40 kya [1]
We present two independent models that capture the internal dynamics of Neanderthal populations―the models ignore, among other things, competitive interactions with Anatomically Modern Humans (AMHs)―and that suggest that the disappearance of Neanderthals might have resided in the small size of their population(s) alone
When N0 = 50, Neanderthals face a risk of extinction, i.e., Irisk falls in the range 0.58–3.2
Summary
A long-standing enigma in palaeoanthropology is the demise of Neanderthals approximately 40 kya [1]. What is uncertain are the causes of Neanderthal extinction. It has been attributed to a wide variety of intensely debated factors, including climatic change ([13,14,15,16,17], but see [18,19]), epidemics [20,21], a superiority of AMHs over Neanderthals in competing for the same resources ([22,23,24,25,26,27,28,29,30,31,32,33,34] but see [18]). Not surprisingly, confirmed that if such superiority is assumed [35,36,37,38,39,40,41], Neanderthals would have been likely to go extinct.
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