1Pathology and Anatomical Sciences, University of Missouri, 2Human Origins Program, National Museum of Natural History, Smithsonian Institution, 3Anthropology, University of Arkansas, 4College of Mines and Earth Sciences, University of Utah, 5Earth Sciences, National Museums of Kenya
Friday 8:15-8:30, Ballroom B
Despite recent discoveries of relatively complete hands from two early hominin species (Ardipithecus ramidus and Australopithecus sediba), fundamental questions remain about the evolution of human-like hand anatomy and function. These questions are driven by the paucity of hominin hand fossils between 1.8 and 0.8 million years old. In 2010, a team from the West Turkana Paleontology Project of the National Museums of Kenya recovered a hominin third metacarpal (KNM-WT 51260) from the newly discovered site of Kaitio. Kaitio is located in northern Kenya west of Lake Turkana and dates to about 1.4 Ma. In all ways, this bone resembles that of a modern human in overall proportions and morphology. The metacarpal is long, falling within the upper range of modern European and African American males, and is one of the longest hominin third metacarpals known among Neandertals and early modern humans. Notably, KNM-WT 51260 displays a well-developed styloid process, the most distinctive features of the human and Neandertal hand, not present in earlier hominins. The morphological similarity of KNM-WT 51260 to human third metacarpals, and its spatio-temporal context, suggests that this fossil is attributable to Homo erectus sensu lato. KNM-WT 51260 shows that modern human-like hand morphology and function was present within a behavioral context characterized by Acheulean technology. It provides the earliest evidence of a key shared derived characteristic of modern human and Neandertal hands, and suggests that the distinctive complex of radial carpometacarpal joint features in the human hand arose early in the evolution of the genus Homo.
Funding provided by the LSB Leakey Foundation and University of Missouri Research Council.