Femur length, body mass, and stature estimates of Orrorin tugenensis, a 6 Ma hominid from Kenya
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To understand the palaeobiology of extinct hominids it is useful to estimate their body mass and stature. Although many species of early hominid are poorly preserved, it is occasionally possible to calculate these characteristics by comparison with different extant groups, by use of regression analysis. Calculated body masses and stature determined using these models can then be compared. This approach has been applied to 6 Ma hominid femoral remains from the Tugen Hills, Kenya, attributed to Orrorin tugenensis. It is suggested that the best-preserved young adult individual probably weighed approximately 35–50 kg. Another fragmentary femur results in larger estimates of body mass, indicative of individual variation. The length of the femur of the young adult individual was estimated, by using anthropoid-based regression, to be a minimum of 298 mm. Because whole-femur proportions for Orrorin are unknown, this prediction is conservative and should be revised when additional specimens become available. When this predicted value was used for regression analysis of bonobos and humans it was estimated to be 1.1–1.2 m tall. This value should, however, be viewed as a lower limit.
KeywordsOrrorin tugenensis Body-mass estimate Limb length Femur Bipedalism
We thank the director and staff of the Community Museums of Kenya for permission to study the Orrorin specimens under their care, the members of the Kenya Paleontology Expedition for their help in the field, and H. McHenry and anonymous reviewers for their comments on the manuscript. Research permission was obtained from the Ministry of Education, Research and Technology in Kenya. Funds were provided by the Collège de France, the CNRS (GDR 983 & PICS 1048), the Muséum national d’Histoire Naturelle, Paris, the French Ministry of the Foreign Affairs (Commission des Fouilles Archéologiques à l’Etranger) and the 21COE Program (A14), core-to-core program HOPE from the JSPS.
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