Developments in Brief : ‘Black Skull’ Discovery Raises Some New Questions About Primitive Man

Scientists unveiled a fossil last week called the “black skull” that they said supports a theory that there was more than one species of primitive man 3 million years ago.

“This throws cold water on the notion that as recently as 3 million years ago there was only one species which gave rise to the others,” said Richard Leakey, Kenya’s national museums director and a member of the expedition that discovered the fossil in August, 1985.

The skull is that of an adult male who roamed the western shores of Lake Turkana in remote northern Kenya more than 2 1/2 million years ago. It is the oldest specimen ever found of a species of early man called Australopithecus boisei.

It has extremely primitive characteristics, including an apelike forward-thrusting face and a brain that is “the smallest of any fossil hominid measured to date,” the scientists said. The brain was about the size of that of a modern ape, and less than a third the size of a human brain, they said.

“It came as a surprise to us when this turned up, and I think some of our colleagues are in for a shock,” said Prof. Alan Walker, a Harvard-trained scientist from Braunstone, Leicester, in England, who discovered the skull.

The finding strongly questions a rival school of thought led by American paleontologist Don Johanson that at that time there was only one type of early man, like Lucy. Lucy is the nearly half-complete skeleton that Johanson discovered in neighboring Ethiopia in 1975, for which he named a species called Australopithecus afarensis.

Eric Delson of the City University of New York said the skull is “the most important find since Lucy.” He said the new species suggests the possibility of a different lineage than is now widely accepted for human ancestors in the mysterious time period ranging from 4 million to 2 million years ago.

On the oldest side of the gap is the apeman afarensis, represented by Lucy. A commonly accepted view, Delson said, is that the family tree splits after that, with one branch giving rise about 2 million years ago to Homo habilis, which may have led to modern man.

The other branch, the view maintains, led to a species called Australopithecus africanus. That led to two robust species called Australopithecus boisei, which the new find represents, and Australopithecus robustus. This branch was an evolutionary dead end without any descendants alive today.

The new discovery, Delson said, has physical characteristics that suggest it could be a good intermediate between afarensis and the robust species, displacing africanus from that role.

The scientists call it the black skull because of its color; most such fossils are brown or yellow.