Walk Like Us: 1.5 Million-Year-Old Footprints Look Modern

The second-oldest human footprints ever found show that mankind's ancestors walked out of Africa on feet indistinguishable from our own.

The 1.5 million-year-old footprints, found in sediment deposits in northern Kenya, are the oldest identified since Mary Leakey found 3.75 million-year-old tracks preserved in volcanic ash in northern Tanzania. Those prints belonged to Australopithecus afarensis, and provided clear evidence of bipedalism.

Though the short-legged, long-trunked A. Afarensis was able to walk upright, its feet were still apelike, possessing a telltale splayed-out big toe. Because the early fossil record contains no foot bones, scientists didn't know when modern feet — a defining human characteristic necessary for long-distance running — evolved.



The new footprints, described Thursday in Science, apparently belong to Homo erectus. Maker of the first stone tools, H. erectus was also the first hominid to leave Africa, migrating to Asia about two million years ago.

By scanning the footprints with lasers and measuring sediment compression, then comparing the results to A. afarensis and Homo sapiens, researchers determined that H. erectus had a modern foot and stride: a mid-foot arch, straight big toe and heel-to-toe weight transfer.



FootcomparisonsIn a commentary accompanying the study, primatologists Robin Huw Crompton and Todd Pataky say the footprints are "broadly indistinguishable from those of modern humans" and "herald an exciting time for the evolution of human gait."

Citations: "Early Hominin Foot Morphology Based on 1.5-Million-Year-Old Footprints from Ileret, Kenya." By Matthew R. Bennett, John W.K. Harris, Brian G. Richmond, David R. Braun, Emma Mbua, Purity Kiura, Daniel Olago, Mzalendo Kibunjia, Christine Omuombo, Anna K. Behrensmeyer, David Huddart, Silvia Gonzalez. Science, Vol. 323 Iss. 5918, Feb. 26, 2009.