MAR 26 1981, MAR 27 1981; Evidence of a walk in volcanic ash millions of years ago; Anthropologist M

MAR 26 1981, MAR 27 1981; Evidence of a walk in volcanic ash millions of years ago; Anthropologist Mary D. Leakey stands with six-foot-long fiberglass cast of a portion of a 72-foot-long trail made by three hominids 3.6 million years ago as they walked across the ash at the beginning of a rainy season on an East African plain in what is now northern Tanzania. She presented the cast to the Denver Museum of Natural History Thursday and gave a lecture about the trail of fossilized footprints.; (Photo By Lyn Alweis/The Denver Post via Getty Images)