Mary Douglas Leakey was recognized in her lifetime as one of the world’s most distinguished fossil hunters. In 1974 Mary BEGINS work at Laetoli, 30 miles from Olduvai Gorge. It is here that Mary and her team found amazingly well preserved hominid footprints in volcanic beds, known as tuffs. The footprint tuff of 1976 has a potassium argon date of 3.5-3.8 mya, evidence of upright walking that supported Donald Johansen's find, Lucy, also known as Australopithecus Afarensis, though Mary Leakey has rejected this( she believe that the belong to the genus homo). Eighty feet of trail had been uncovered by 1979, leaving researchers to speculate that it was three hominids, possibly a family, that left their mark millions of years ago.
