Evidence of early human ancestors, probably hominids known as australopithecines who lived about 2.3 million years ago, has been found in eastern Zaire, well outside their known range.

The evidence consists of the simplest known form of stone tools, mostly crude flakes with sharp edges. No hominid skeletal remains have been found in Zaire, but they have long been known from more intensively studied areas of Ethiopia, Kenya, Tanzania and South Africa. Similar stone tools of greater age have been found in Ethiopia.

While earlier discoveries involved only a few sites, most experts on human evolution have assumed that early hominids lived throughout large regions of Africa. The discovery in Zaire confirms this assumption and adds a new region in which scientists can search for evidence of human evolution.

Australopithecines, members of the genus Australopithecus, are the earliest known human ancestors to descend from the ape. Current thinking holds that they evolved into the first true humans, Homo habilis, less than 2 million years ago.

The discovery was announced last month by the three leaders of an American expedition -- Noel T. Boaz of the Virginia Museum of Natural History, John W.K. Harris of the University of Wisconsin and Alison S. Brooks of George Washington University and the Smithsonian Institution.