'Missing link' is found in Ethiopia

ONE OF the most important discoveries in human evolution has identified a small-brained ape who walked on two legs as the strongest contender yet to be described as the "missing link".

Scientists excavating in a remote part of Ethiopia have found a new species of ape-like animal that lived about 2.5 million years ago and which could be the first human ancestor to eat meat with the help of stone tools. The international team of scientists presents details of itsfindings today in the journal Science, which trumpets the discovery as "dramatic evidence" of butchery being the oldest profession.

Anthropologists involved in the study believe the ability to use tools to cut meat and crush bones could have provided the burst in nutrition necessary for early human ancestors to develop larger brains.

Tim White, a biologist at the University of California-Berkeley who led a research group, said the invention of tools to butcher animals would have led to unprecedented access to a high-fat diet of meat and marrow, necessary for brain development.

The new hominid species, called Australopithecus garhi, had a brain capacity of about 450 cubic centimetres - compared with the 1,400 cubic centimetres of modern humans - and lived in east Africa between two and three million years ago, a crucial period in evolution just before the emergence of the human family.

"You go into this period with, in essence, bipedal, big-toothed chimps and come out with meat-eating, large-brained hominids. That's a big change in a relatively short time. We'd really like to know more about what happened there," Professor White said.

The researchers made three independent discoveries outside the small village of Bouri, north-east of Addis Ababa. They found part of the skull of A garhi, which enabled them to classify it as a new species, and the leg and arm bones of a second individual, which lived at the same time and is likely to belong to the same species.

The third find, just a few feet away from the skeletal remains, included the bones of antelopes, horses and other animals, which showed clear signs of having been butchered with stone tools.

Some of the bones were crushed or broken off at both ends, indicating the extraction of marrow. Others had curved cut marks, including some found on an antelope's jawbone, presumably to remove the tongue.

Although stone tools from this period have been found, this is the first evidence that they were used for butchering animals, the scientists said.

"Marrow is rich in fat, and few animals other than humans and hyenas can get at it. Anthropologists have theorised that just such a dietary breakthrough allowed the dramatic increase in brain size," says an editorial in Science. Other scientists have proposed that the dietary breakthrough might instead have been the discovery of how to cook root vegetables, which would have provided a rich source of digestible carbohydrates.