Born to Run (and Run and Run...)

Ask, Apr 2005 by Cooper, Sharon Katz

More than four million years ago, ancient human ancestors First stood up and began walking on two legs. These early walkers may no longer have moved like apes, but they still looked a lot like them, with short legs, long arms, and hunched shoulders. Now, after 13 years of research, scientists studying fossils of early humans have concluded that the human body didn't begin to look, well, human until our ancestors evolved the ability not just to walk but to run.

Like apes, the first human walkers could run for short periods, but it was two or three million years before the human body adapted for running long distances. According to the study, early humans developed longer legs as well as springy tendons in their legs and feet to help make taking broad running strides easier. Arms got shorter and rear ends got bigger to help keep the body balanced. These changes not only turned early humans into champion distance runners but also made them look more human and less apelike.

Why did humans start running? Maybe because they were hungry. Other animals, such as antelopes, can run faster than humans for short distances, but humans can run for longer without getting tired. By running great distances at a steady pace, early humans could exhaust their prey, then eat it for dinner.

-Sharon Katz Cooper