Early Pleistocene third metacarpal from Kenya and the evolution of modern human-like hand morphology

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• Tocheri, Matthew W.
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• Plavcan, J. Michael
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• Brown, Francis H.
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• Manthi, Fredrick Kyalo

Abstract

A newly discovered metacarpal from Kaitio, Kenya, dates to 1.42 Mya and provides evidence for the evolution of the modern human hand more than 600,000 y earlier than previously documented. This bone displays a styloid process, which is part of a distinctively human rearrangement of the wrist associated with enhanced hand function when making and using tools. Prior to this discovery, the first evidence of this anatomy was found only in post-Homo erectus archaic humans. This new find documents its appearance much earlier in time and suggests that an increased reliance on manipulatory behaviors indicated by the archeological record early in the Pleistocene selected for the modern human hand early in the evolution of the genus Homo.