Integrative Anatomy Program, Department of Pathology and Anatomical Sciences, University of Missouri, Columbia, MO 65212.
Proc Natl Acad Sci U S A. 2014 Jan 7;111(1):121-4. doi: 10.1073/pnas.1316014110. Epub 2013 Dec 16.
Despite discoveries of relatively complete hands from two early hominin species (Ardipithecus ramidus and Australopithecus sediba) and partial hands from another (Australopithecus afarensis), fundamental questions remain about the evolution of human-like hand anatomy and function. These questions are driven by the paucity of hand fossils in the hominin fossil record between 800,000 and 1.8 My old, a time interval well documented for the emergence and subsequent proliferation of Acheulian technology (shaped bifacial stone tools). Modern and Middle to Late Pleistocene humans share a suite of derived features in the thumb, wrist, and radial carpometacarpal joints that is noticeably absent in early hominins. Here we show that one of the most distinctive features of this suite in the Middle Pleistocene to recent human hand, the third metacarpal styloid process, was present ∼1.42 Mya in an East African hominin from Kaitio, West Turkana, Kenya. This fossil thus provides the earliest unambiguous evidence for the evolution of a key shared derived characteristic of modern human and Neandertal hand morphology and suggests that the distinctive complex of radial carpometacarpal joint features in the human hand arose early in the evolution of the genus Homo and probably in Homo erectus sensu lato.
尽管已经发现了两个早期人类物种（阿法南方古猿和南方古猿源泉种）相对完整的手以及另一个物种（南方古猿非洲种）的部分手，但关于人类手部解剖结构和功能的演化仍存在一些基本问题。这些问题是由人类化石记录中在 80 万至 180 万年前之间的手部化石稀少所驱动的，这一时间间隔为阿舍利技术（两面打制石器）的出现和随后的扩散提供了很好的记录。现代人和中更新世至晚更新世人类的拇指、手腕和桡腕掌骨关节都具有一系列衍生特征，而这些特征在早期人类中明显缺失。在这里，我们展示了中更新世至现代人类手部的这套特征中最具特色的一个特征，即第三掌骨茎突，在肯尼亚图尔卡纳湖西岸的凯特遗址的一个东非人类化石中，约有 142 万年的历史。因此，这个化石为现代人类和尼安德特人手部形态的一个关键共同衍生特征的演化提供了最早的明确证据，并表明人类手部桡腕掌骨关节特征的独特组合可能在人属的早期演化中就出现了，而且很可能在广义的直立人时期就出现了。
