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Thread: Why Hunter-Gatherer Populations do not show Signs of Pleistocene Demographic Expansion

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    Why Hunter-Gatherer Populations do not show Signs of Pleistocene Demographic Expansion

    Why hunter-gatherer populations do not show signs of pleistocene demographic expansions.

    Excoffier L, Schneider S.

    Genetics and Biometry Laboratory, Department of Anthropology, University of Geneva, CP 24, 1211 Geneva 24, Switzerland. Laurent.Excoffier@anthro.unige.ch

    The mitochondrial DNA diversity of 62 human population samples was examined for potential signals of population expansions. Stepwise expansion times were estimated by taking into account heterogeneity of mutation rates among sites. Assuming an mtDNA divergence rate of 33% per million years, most populations show signals of Pleistocene expansions at around 70,000 years (70 KY) ago in Africa and Asia, 55 KY ago in America, and 40 KY ago in Europe and the Middle East, whereas the traces of the oldest expansions are found in East Africa (110 KY ago for the Turkana). The genetic diversity of two groups of populations (most Amerindian populations and present-day hunter-gatherers) cannot be explained by a simple stepwise expansion model. A multivariate analysis of the genetic distances among 61 populations reveals that populations that did not undergo demographic expansions show increased genetic distances from other populations, confirming that the demography of the populations strongly affects observed genetic affinities. The absence of traces of Pleistocene expansions in present-day hunter-gatherers seems best explained by the occurrence of recent bottlenecks in those populations, implying a difference between Pleistocene (approximately 1,800 KY to 10 KY ago) and Holocene (10 KY to present) hunter-gatherers demographies, a difference that occurred after, and probably in response to, the Neolithic expansions of the other populations.

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    Post hunter-gatherer populations do not show signs of pleistocene demographic expansions.

    Proc Natl Acad Sci U S A. 1999 Sep 14;96(19):10597-602. Related Articles, Links


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    Proc Natl Acad Sci U S A. 1999 Sep 14;96(19):10562-3.

    Why hunter-gatherer populations do not show signs of pleistocene demographic expansions.

    Excoffier L, Schneider S.

    Genetics and Biometry Laboratory, Department of Anthropology, University of Geneva, CP 24, 1211 Geneva 24, Switzerland. Laurent.Excoffier@anthro.unige.ch

    The mitochondrial DNA diversity of 62 human population samples was examined for potential signals of population expansions. Stepwise expansion times were estimated by taking into account heterogeneity of mutation rates among sites. Assuming an mtDNA divergence rate of 33% per million years, most populations show signals of Pleistocene expansions at around 70,000 years (70 KY) ago in Africa and Asia, 55 KY ago in America, and 40 KY ago in Europe and the Middle East, whereas the traces of the oldest expansions are found in East Africa (110 KY ago for the Turkana). The genetic diversity of two groups of populations (most Amerindian populations and present-day hunter-gatherers) cannot be explained by a simple stepwise expansion model. A multivariate analysis of the genetic distances among 61 populations reveals that populations that did not undergo demographic expansions show increased genetic distances from other populations, confirming that the demography of the populations strongly affects observed genetic affinities. The absence of traces of Pleistocene expansions in present-day hunter-gatherers seems best explained by the occurrence of recent bottlenecks in those populations, implying a difference between Pleistocene (approximately 1,800 KY to 10 KY ago) and Holocene (10 KY to present) hunter-gatherers demographies, a difference that occurred after, and probably in response to, the Neolithic expansions of the other populations.

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    Post Re: hunter-gatherer populations do not show signs of pleistocene demographic expansions.

    The absence of traces of Pleistocene expansions in present-day hunter-gatherers seems best explained by the occurrence of recent bottlenecks in those populations, implying a difference between Pleistocene (approximately 1,800 KY to 10 KY ago) and Holocene (10 KY to present) hunter-gatherers demographies, a difference that occurred after, and probably in response to, the Neolithic expansions of the other populations.
    Thats a good proof for my idea that today hunter-gatherers doesnt live and act like the h-g of the past which were more "expansive", more growth oriented.

    Because I had the discussion that they might have act in the same way as modern h-g, and that the change to the Neolithic subsistence pattern was just the result of natural environmental changes+war alone and not human caused changes in demography and environment, because they had no birth control and expanded in populations size without leaving the fertile regions too.
    Today H-G always try to preserve the ressources as much as possible, thats something I think we cannot assume for the early expansive cultures, because otherwise they would have stayed in Africa, plain and simple, in regions in which they could have survived without growth and more competition without problems.

    The culture and character of the expansive groups might be totally different and the assumption that we can always look at today h-g to know how the expansive ones lived might be not always true.

    Those populations which had many bottlenecks adapted themselves to a "cautious" economy and subsistence pattern because of their knowledge of catastrophies in their small (because of agricultural expansion) territories.
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