The son of paleoanthropologists Mary Leakey and Louis Leakey,Richard Erskine Frere Leakey was born on December 19, 1944, in Nairobi, Kenya. Continuing the work of his parents, Leakey has pushed the date for the appearance of the first true humans back even further than they had, to nearly three million years ago. This represents nearly a doubling of the previous estimates. Leakey also has found more evidence to support his father's still controversial theory that there were at least two parallel branches of human evolution, of which only one was successful.

His paleontological career began in 1963, when he led a team of paleontologists to a fossil-bearing area near Lake Natron in Tanganyika (now Tanzania), a site that was later dated to approximately 1.4 million years ago. A member of the team discovered the jaw of an early hominid--a member of the family of erect primate mammals that use only two...