Lucy Gets a Younger Sister

By Anastasia Toufexis

"Whoa. This is a hominid," crowed Anthropologist Tim White when he spotted the first bone fragment, a portion of an elbow, lying on a layer of sand. Looking down, Expedition Leader Donald Johanson shouted, "There's part of a humerus right next to it!" That July 1986 find in Tanzania's Olduvai Gorge marked the beginning of a startling discovery that was formally unveiled last week by White and Johanson. The team of ten U.S. and Tanzanian scientists unearthed 302 fossil bones and teeth that have yielded a more complete picture of modern humans' earliest direct ancestor, Homo habilis. The new material could alter the way scientists interpret human evolution.

Until now, most anthropologists have believed that Homo habilis, a species that lived in eastern and southern Africa between 2 million and 1.5 million years ago, stood about the same height and had the same body build as Homo erectus, its successor. Homo habilis (literally, handy man) was the first human ancestor to make stone tools. The new Olduvai Gorge skeleton, however, suggests that Homo habilis was much smaller and more apelike than previously thought. If that is the case, says Johanson, the modern body type probably did not evolve until Homo erectus emerged some 1.6 million years ago. Moreover, the evolutionary changes leading to Homo erectus, which preceded modern man, must have occurred faster than has been supposed.

Earlier discoveries of Homo habilis fossils consisted only of skulls, teeth and questionable limb bones, forcing scientists to guess at the creature's size and proportions. But the dramatic new find, which includes skull, arm bones, thigh and shin fragments from a single adult female, permits a more accurate assessment. The length of the thigh bone is a gauge of height, and the relative length of the upper arm bone to the upper leg bone is a vital clue to body build. The remains, described in the British journal Nature last week, belong to a creature that lived about 1.8 million years ago and stood no more than 3 1/2 feet tall. Says Johanson, director of the Institute of Human Origins in Berkeley: "This may be the smallest hominid ever found."

The proportions of the skeleton were also a surprise to the scientists. The upper arm bone is about 95% as long as the thigh bone, indicating that the arms dangled to the knees, much as they do in apes. Thus Homo habilis closely resembled Australopithecus afarensis, of which the best-known example is the famed "Lucy" skeleton, which was discovered by Johanson in 1974. Lucy's ratio is 85%; in modern humans, the figure is about 70% to 75%.

) Observes Johanson: "The new specimen suggests that the body pattern we call modern did not appear until Homo erectus and that it happened fairly rapidly." Says White, a professor at the University of California, Berkeley: "The question is, Why did they lose those features, and what made them change in just 200,000 years?"

The only thing that seems sure at this point, White adds, "is that we're looking at a major transition in human evolution involving behavior and anatomy. Something major and dramatic happened here."

With reporting by Andrea Dorfman/New York