More than 2.5 million years ago, human-like creatures were using stone tools to filet meat beside an African lake, a discovery researchers say provides a new human ancestor and also the earliest known use of tools to cut food.
The researchers named the new hominid species "garhi," which means surprise in the local language near Bouri, in Ethiopia's Afar desert.
The new species is descended from the one that produced the famous Lucy skeleton in east Africa. It is a candidate for earliest human ancestor, the researchers say in an article in Friday's issue of the journal Science.
"It is in the right place, at the right time, to be the ancestor of early [humans], however defined," reported the team led by Berhane Asfaw of Rift Valley Research Service in Addis Ababa, Ethiopia, and Tim White of the University of California at Berkeley.
The new species "could turn out to be the link" between the genus Homo, which includes modern humansÂ—Homo sapiensÂ—and its predecessor, Australopithecus, White said in a telephone interview.
Not so sure is anthropologist Bernard Wood of George Washington University in Washington.
"I think it's always good news when people find more fossil evidence," he said in a telephone interview, "but ... I don't think we can be sure it's an ancestor of later" humans.
"What they've found is what many of us were expecting, that there is quite a lot of variety in early hominids ... in this particular period," Wood said. "I think it's ironic in some ways that it's been called a surprise."
Tentatively named Australopithecus garhi, the new species had large teeth and a projecting face, somewhat similar to the well-known fossil Lucy, who lived 3.2 million years ago and was of the Australopithecus afarensis species, with apelike upper arms that were long relative to her legs.
By the time the more human-like Homo erectus developed, about 1.7 million years ago, legs were longer and more human, and forearms had shortened.
Based on the relationship between arm and leg bones from a second individual found near the new skull, garhi was between the two, with long, human-like legs but not yet having shortened forearms.
The skull was from a male, with a small brain case and a protruding jaw. The individual whose arm and leg bones were found would have been about 4-feet-10, White said.
An antelope jaw and other animal bones found near the garhi skeleton show cut marks from tools, perhaps the earliest evidence of human tool use in butchering animals.
"All of a sudden this is a bipedal primate with a difference," White said.
"We now have the clearest evidence these very early hominids were butchering mammals and were knowledgeable about the (marrow) within the bones, a highly valuable food resource," he added.
The presence of the tools and the bones together "doesn't proe that the individual was the one who held the stone tool, but it's pretty strong evidence," he went on.
By Randolph E. Schmid