Neanderthals: Bad luck and its part in their downfall
07 April 2011 by Mark Buchanan
Magazine issue 2807.
AS OUR ancestors moved north out of Africa and onto the doorstep to the rest of the world, they came across their long-lost cousins: the Neanderthals. As the popular story goes, the brutish hominins were simply no match for cultured, intelligent Homo sapiens and quickly went extinct.
Maybe, but it's also possible that Neanderthals were simply unlucky and disappeared by chance, mathematicians propose.
No hard feelings, cousin (Image: Frank Franklin II/AP/PA)
We know that humans and Neanderthals got pretty cosy during their time together in the Middle East, 45,000 years ago. Between 1 and 4 per cent of the DNA of modern non-Africans is of Neanderthal origin, implying their ancestors must have interbred before humans moved into Europe (New Scientist, 15 May 2010, p 8).
The popular theory has it that humans soon displaced Neanderthals thanks to their superior skills and adaptations. But mathematicians Armando Neves at the Federal University of Minas Gerais in Belo Horizonte, Brazil, and Maurizio Serva at the University of Aquila, Italy, now say that the extinction of Neanderthals may have been down to a genetic lottery.
When two populations interbreed, one of them can go extinct simply due to the random mixing of their genes through sexual reproduction.
To find out if this could have wiped out Neanderthals, Neves and Serva modelled the populations that met in the Middle East. Using very few assumptions, they estimated the rate of interbreeding that would lead to the observed share of Neanderthal DNA.
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Read more here/Leia mais aqui: New Scientist
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Extremely rare interbreeding events can explain Neandertal DNA in modern humans
(Submitted on 23 Mar 2011)
Considering the recent experimental discovery of Green et al that present day non-Africans have 1 to 4% of their nuclear DNA of Neandertal origin, we propose here a model which is able to quantify the interbreeding events between the two subpopulations. The model consists of a solvable system of deterministic ordinary differential equations containing as a stochastic ingredient a realization of the Wright-Fisher drift process. By simulating the model we are able to apply it to the interbreeding of African and Neandertal subpopulations and estimate the only parameter of the model, which is the number of individuals per generation exchanged between subpopulations. Our results indicate that the amount of Neandertal DNA in non-Africans can be explained with maximum probability by the exchange of a single pair of individuals between the subpopulations at each 77 generations, but larger exchange frequencies are also allowed with sizable probability.
Comments: 23 pages, 4 figures
Subjects: Populations and Evolution (q-bio.PE); Mathematical Physics (math-ph); Probability (math.PR)
MSC classes: 92D15 (Primary) 60J10 (Secondary)
Cite as: arXiv:1103.4621v1 [q-bio.PE]
Submission historyFrom: Armando G. M. Neves [view email]
[v1] Wed, 23 Mar 2011 20:23:11 GMT (113kb,D)
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