Fossil footprints puzzle scientists: Bear or ancient human? - KSL.com

Leakey focused her attention instead on other fossil footprints that could be more clearly linked to early humans.

Those footprints, found at a site called Laetoli G, are the first clear evidence of early humans walking upright.

Other factors, such as the spacing of the footprints, led the study authors to conclude that that the footprints were left by a previously unknown species of a very early human ancestor.

Smithsonian's Potts said it's a toss-up between an ancient bear or an ancient human, adding that an ancient bear may have walked differently than a modern black bear.