Stringer Chris
Department of Earth Sciences, The Natural History Museum, London SW7 5BD, UK
Philos Trans R Soc Lond B Biol Sci. 2016 Jul 5;371(1698). doi: 10.1098/rstb.2015.0237.
If we restrict the use of Homo sapiens in the fossil record to specimens which share a significant number of derived features in the skeleton with extant H. sapiens, the origin of our species would be placed in the African late middle Pleistocene, based on fossils such as Omo Kibish 1, Herto 1 and 2, and the Levantine material from Skhul and Qafzeh. However, genetic data suggest that we and our sister species Homo neanderthalensis shared a last common ancestor in the middle Pleistocene approximately 400-700 ka, which is at least 200 000 years earlier than the species origin indicated from the fossils already mentioned. Thus, it is likely that the African fossil record will document early members of the sapiens lineage showing only some of the derived features of late members of the lineage. On that basis, I argue that human fossils such as those from Jebel Irhoud, Florisbad, Eliye Springs and Omo Kibish 2 do represent early members of the species, but variation across the African later middle Pleistocene/early Middle Stone Age fossils shows that there was not a simple linear progression towards later sapiens morphology, and there was chronological overlap between different 'archaic' and 'modern' morphs. Even in the late Pleistocene within and outside Africa, we find H. sapiens specimens which are clearly outside the range of Holocene members of the species, showing the complexity of recent human evolution. The impact on species recognition of late Pleistocene gene flow between the lineages of modern humans, Neanderthals and Denisovans is also discussed, and finally, I reconsider the nature of the middle Pleistocene ancestor of these lineages, based on recent morphological and genetic data.This article is part of the themed issue 'Major transitions in human evolution'.
如果我们将化石记录中智人的使用范围限制在与现存智人在骨骼上具有大量衍生特征的标本上,那么基于诸如奥莫基比什1号、赫托1号和2号等化石以及来自斯胡尔和卡夫泽的黎凡特材料,我们这个物种的起源将被置于非洲晚更新世中期。然而,基因数据表明,我们和我们的姊妹物种尼安德特人在更新世中期大约40万至70万年前有一个最后的共同祖先,这比上述化石所表明的物种起源至少早20万年。因此,非洲化石记录很可能会记录智人谱系的早期成员,这些成员只显示出该谱系晚期成员的一些衍生特征。在此基础上,我认为来自杰贝尔伊鲁德、弗洛里斯巴德、埃利耶泉和奥莫基比什2号等地的人类化石确实代表了该物种的早期成员,但非洲晚更新世中期/中石器时代早期化石的变异表明,向晚期智人形态并没有简单的线性发展过程,不同的“古老”和“现代”形态之间存在时间上的重叠。即使在非洲内外的晚更新世,我们也发现了智人标本,它们明显超出了该物种全新世成员的范围,这显示了近期人类进化的复杂性。本文还讨论了晚更新世现代人类、尼安德特人和丹尼索瓦人谱系之间基因流动对物种识别的影响,最后,我根据最近的形态学和基因数据重新审视了这些谱系更新世中期祖先的性质。本文是主题为“人类进化的重大转变”的特刊的一部分。