1] Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, 04103 Leipzig, Germany [2] Department of Cell and Developmental Biology, University College London, London WC1E 6BT, UK.
Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, 04103 Leipzig, Germany.
Nature. 2015 Mar 5;519(7541):83-6. doi: 10.1038/nature14224.
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 Homo fossils. 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 sapiens or H. erectus. We find that this shape variability is not consistent with a single species of early Homo. 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.
除了直立人（广义），东非早期人类的化石记录被解释为代表单一可变物种，能人，或两个物种。然而，在后一种情况下，对于各自的分组没有共识，而且哪两个物种包括 OH 7，即 180 万年前的能人模式标本。这个来自奥杜威峡谷的部分头骨和手对于评估人类谱系的早期进化至关重要，并通过优先名称来确定这两个分类群中的一个或另一个。然而，OH 7 下颌骨的扭曲保存阻碍了将该标本与其他化石进行比较的尝试。在这里，我们提出了 OH 7 下颌骨的虚拟重建，并将其与其他早期人类化石进行了比较。重建的下颌骨非常原始，具有长而窄的牙弓，与南方古猿 afarensis 相似，而不是与智人或直立人衍生的抛物线牙弓相似。我们发现这种形状的可变性与单一的早期人类物种不一致。重要的是，OH 7 的下颌形态与分配给 Homo rudolfensis 的化石以及 A.L. 666-1 上颌骨不兼容。后者在形态上比 OH 7 更衍生，但比 OH 7 年长 50 万年，这表明能人谱系起源于 230 万年前之前，从而标志着人类属中的物种多样性根深蒂固。我们还重建了 OH 7 的顶骨并估计了它的颅腔容量。其在 729 到 824 毫升之间，大于以前发表的任何值，这强调了早期人类物种之间大脑大小的近乎完全重叠。我们的结果阐明了能人假设，但对其系统发育关系提出了疑问。早期人类物种之间的差异似乎更多地以颌骨多样性为特征，而不是以大脑大小的差异为特征，而所有分类群的大脑大小都高度可变。
