Early Humans Toed the Line

More than 1.5 million years ago, several human ancestors wandered across a mud flat at what is now Ileret, Kenya. The footprints they left behind, the second oldest ever found, reveal that these early humans had evolved big, modern feet--and that they walked just like we do, according to a new study.


Ancient Footsteps. This 1.5-million-year-old footprint
is as big as a modern human's foot
and indicates its maker had a gait like ours.

Human ancestors began walking upright at least 6 million years ago, according to analysis of hominid leg and pelvic bones. But researchers have debated when they evolved the ability to walk upright in a modern manner, rather than with a more primitive gait, possibly like the bent-kneed waddle of chimpanzees.

Footprints found in Laetoli, Tanzania, show that the australopithecines that made them 3.75 million years ago had longer toes, a shallower arch, and a more apelike big toe that jutted slightly away from the other toes. This suggested to some that they had a more primitive gait and that the transition to fully modern walking didn't happen until our direct ancestor, Homo erectus, emerged about 1.9 million years ago. However, researchers had few fossils of the foot of H. erectus to prove it walked just like we do.

Now, with the discovery of the footprints, which were probably made by H. erectus, at Ileret, they have direct evidence of how it walked.

http://sciencenow.sciencemag.org/cgi/content/full/2009/226/1