A study suggests how the human foot evolved to facilitate bipedalism. The adoption of bipedal locomotion was a critical step in human evolution. To understand the process by which early hominins adapted to bipedalism, Peter Fernández and colleagues compared the morphologies of the metatarsophalangeal joints (MTPJs), at the base of the toes, in fossil hominins, modern humans, apes, and monkeys. Hominins were distinguished from other primates largely by the degree of dorsal doming of the metatarsal heads, or the extent to which the dorsal surface of the head protrudes above the shaft, suggesting that dorsal doming, which correlates with MTPJ range of motion, was important for bipedal locomotion. The lateral metatarsals of the oldest fossil hominin examined, Ardipithecus ramidus , resembled those of modern humans with respect to dorsal doming, suggesting that adaptations for bipedal walking in the lateral metatarsals appeared early in hominin evolution, more than 4.4 million years ago. However, the first metatarsal, which connects to the big toe, of Ar. ramidus did not resemble that of modern humans, with human-like morphology appearing only in later hominins, mainly those within the genus Homo . The latter finding suggests that while adapting to bipedal locomotion, early hominin feet may have retained some grasping capability, with a fully bipedal-adapted big toe evolving relatively recently, according to the authors.
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Article #18-00818: "Evolution and function of the hominin forefoot," by Peter J. Fernandez et al.
MEDIA CONTACT: Peter J. Fernández, Marquette University, Milwaukee, WI; tel: 414-288-5725; e-mail: pedro.fernandez@marquette.edu
Proceedings of the National Academy of Sciences