Ray Nicolas, Currat Mathias, Berthier Pierre, Excoffier Laurent
Computational and Molecular Population Genetics Lab, Zoological Institute, University of Bern, 3012 Bern, Switzerland.
Genome Res. 2005 Aug;15(8):1161-7. doi: 10.1101/gr.3708505.
Most genetic and archeological evidence argue in favor of a recent and unique origin of modern humans in sub-Saharan Africa, but no attempt has ever been made at quantifying the likelihood of this model, relative to alternative hypotheses of human evolution. In this paper, we investigate the possibility of using multilocus genetic data to correctly infer the geographic origin of humans, and to distinguish between a unique origin (UO) and a multiregional evolution (ME) model. We introduce here an approach based on realistic simulations of the genetic diversity expected after an expansion process of modern humans into the Old World from different possible areas and their comparison to observed data. We find that the geographic origin of the expansion can be correctly recovered provided that a large number of independent markers are used, and that precise information on past demography and potential places of origins is available. In that case, it is also possible to unambiguously distinguish between a unique origin and a multiregional model of human evolution. Application to a real human data set of 377 STR markers tested in 22 populations points toward a unique but surprising North African origin of modern humans. We show that this result could be due to ascertainment bias in favor of markers selected to be polymorphic in Europeans. A new estimation modeling this bias explicitly reveals that East Africa is the most likely place of origin for modern humans.
大多数基因和考古学证据都支持现代人类起源于撒哈拉以南非洲，且是近期独特起源的观点，但相对于人类进化的其他假说，从未有人尝试过量化这一模型的可能性。在本文中，我们研究了利用多位点基因数据正确推断人类地理起源，并区分独特起源（UO）和多地区进化（ME）模型的可能性。我们在此介绍一种方法，该方法基于对现代人类从不同可能区域扩张到旧世界后预期的遗传多样性进行逼真模拟，并将其与观测数据进行比较。我们发现，只要使用大量独立标记，并且有关于过去人口统计学和潜在起源地的精确信息，扩张的地理起源就能被正确推断出来。在这种情况下，也能够明确区分人类进化的独特起源模型和多地区模型。将该方法应用于在22个群体中测试的377个STR标记的真实人类数据集，结果表明现代人类起源于北非，这一结果独特却令人惊讶。我们表明，这一结果可能是由于偏向选择在欧洲人中具有多态性的标记所导致的确定偏差。一个明确模拟这种偏差的新估计表明，东非是现代人类最有可能的起源地。
