Manderscheid E J, Rogers A R
Department of Anthropology, University of Utah, Salt Lake City, Utah 84112, USA.
Am J Phys Anthropol. 1996 May;100(1):1-5. doi: 10.1002/(SICI)1096-8644(199605)100:1<1::AID-AJPA1>3.0.CO;2-3.
The replacement hypothesis of modern human origins holds that the original population of modern humans expanded throughout the world, replacing existing archaic populations as it went. If this expanding population interbred with the peoples it replaced, then some archaic mitochondria might have been introduced into the early modern gene pool. Such mitochondria would be recognizable today because they should differ from other modern mitochondria at several times the number of sites that we are used to seeing in pairwise comparisons. In this paper we ask what can be inferred from the absence of these "divergent" mitochondria from modern samples. We show that if the effective number of females in our species has been large for the past 40,000 years, then the level of admixture must have been low. For example, if this effective number exceeded 1.6 million, then we can reject the hypothesis that more more than 2/1,000 of the mitochondria in the early modern population derived from admixture with archaic peoples. We argue elsewhere that regional continuity would be detectable in the fossil record only if the rate of admixture exceeded 76%. Here, we show that this level of admixture would require the effective female size of the human population to have been less than 1,777 for the past 40,000 years.
现代人类起源的替代假说认为，现代人类的原始种群在全球范围内扩张，在扩张过程中取代了现有的古代种群。如果这个扩张的种群与被其取代的人群进行了杂交，那么一些古代线粒体可能会被引入早期现代基因库。如今这样的线粒体是可以识别的，因为它们在一些位点上的差异程度应该是我们在两两比较中所常见差异程度的数倍。在本文中，我们探讨从现代样本中不存在这些“差异”线粒体能够推断出什么。我们表明，如果在过去4万年里我们这个物种中有效的女性数量一直很大，那么杂交的程度肯定很低。例如，如果这个有效数量超过160万，那么我们就可以否定早期现代人群中超过2/1000的线粒体源自与古代人群杂交的假说。我们在其他地方指出，只有当杂交率超过76%时，才能在化石记录中检测到区域连续性。在这里，我们表明，过去4万年里，这种杂交程度要求人类种群中有效的女性数量少于1777人。
