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Nature封面故事: “能人”的新形象

摘要 : 本期封面所示为基于来自坦桑尼亚Olduvai Gorge、距今180万年的模式标本Olduvai Hominid 7 (OH 7) 的骨头重建的一个 “能人”(Homo habilis)头骨。

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本期封面所示为基于来自坦桑尼亚Olduvai Gorge、距今180万年的模式标本Olduvai Hominid 7 (OH 7) 的骨头重建的一个 “能人”(Homo habilis)头骨。

透明部分是基于来自肯尼亚的编号为KNM-ER 1813的头盖,将其进行了变形处理,以适合OH 7。 “能人”首次在1964年4月4日的Nature杂志上首次介绍,当时将其作为 “人属”的已知最早成员。此后这些年存在的挑战一直是,弄清其他哪些化石也属于 “能人”,这一任务因OH 7下颌骨的失真而变得复杂化(这种失真掩盖了其最初形状)。

现在,研究人员利用计算机断层扫描(CT)和3D成像技术对OH 7的下颌骨和穹窿骨进行了最先进的虚拟重建,以重新排列破碎了的部分。 该“能人”标本有了新的形象:它有一个原始下颌的形状(与 “阿法南方古猿”即 “露西”的下颌形状相似),同时又有一个与早期 “直立人”一样大的大脑。这一新证据表明,“人属”的多个演化分支的存在时间远远超过距今200万年前。

封面图片:P. Gunz, S. Neubauer & F. Spoor

原文链接:Reconstructed Homo habilis type OH 7 suggests deep-rooted species diversity in early Homo

Besides Homo erectus (sensu lato), the eastern African fossil record of early Homo has been interpreted as representing either a single variable species, Homo habilis, or two species. In the latter case, however, there is no consensus over the respective groupings, and which of the two includes OH 7, the 1.8-million-year-old H. habilis holotype. This partial skull and hand from Olduvai Gorge remains pivotal to evaluating the early evolution of the Homo lineage, and by priority names one or other of the two taxa. However, the distorted preservation of the diagnostically important OH 7 mandible has hindered attempts to compare this specimen with other fossils. Here we present a virtual reconstruction of the OH 7 mandible, and compare it to other early Homofossils. The reconstructed mandible is remarkably primitive, with a long and narrow dental arcade more similar to Australopithecus afarensis than to the derived parabolic arcades of Homo sapiensor H. erectus. We find that this shape variability is not consistent with a single species of earlyHomo. importantly, the jaw morphology of OH 7 is incompatible with fossils assigned to Homo rudolfensis and with the A.L. 666-1 Homo maxilla. The latter is morphologically more derived than OH 7 but 500,000 years older, suggesting that the H. habilis lineage originated before 2.3 million years ago, thus marking deep-rooted species diversity in the genus Homo. We also reconstructed the parietal bones of OH 7 and estimated its endocranial volume. At between 729 and 824 ml it is larger than any previously published value, and emphasizes the near-complete overlap in brain size among species of early Homo. Our results clarify the H. habilis hypodigm, but raise questions about its phylogenetic relationships. Differences between species of early Homo appear to be characterized more by gnathic diversity than by differences in brain size, which was highly variable within all taxa.

对应Nature杂志: 2015年3月5日Nature杂志精选

来源: Nature 浏览次数:86

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