New discovery pushes back human history

August 17, 1995

From Correspondent Brian Jenkins

(CNN) -- Ever wonder where we, as humans, came from? How about Australophithecus anamensis? It may be a mouthful, but that's the name scientists have given to a recent discovery that may provide a crucial link to the period where Homo sapiens, or humans, split from apes.

Until recently, "Lucy" was the oldest known "link", however loose, between ancient apes and the modern man or woman. Paleontologists found her bones in Ethiopia two decades ago. After receiving the name Lucy, scientists called her species Australopithecus afarensis. She was a hominid species, and footprints from the same species were later found in Tanzania. The footprints dated human ancestry to about three and a half million years ago.

But that has now changed. A team of scientists has determined that a group of fossils can roughly date human ancestry to four million years. The bones were discovered at two sites near Lake Turkana in Kenya over the past 30 years. Scientist say that unlike "Lucy", this group of fossils are from a different species of the hominid branch called Australophithecus anamensis.

Professor Alan Walker of Pennsylvania State University believes this discovery is very significant.

"It means that we can put back the origins of one of human's particular attributes: walking upright on two legs." Says Walker, "We can put that back another half million years."

The key find was made last year by Meave Leavey, the wife of famed anthropologist Richard Leavey. She found parts of a shin bone which connected to the knee and ankle. The shapes indicate the animal walked upright. It weighed about 120 pounds, and unlike ape ancestors, would not have been able to grasp a tree branch with its big toe. Therefore, even though this animal was hairy and resembled apes, it's most likely a predecessor of modern humans.

"Australopithecus were bi-pedal," says Professor Walker. "They had ape-sized brains, small brains. They had very large teeth with very thick enamel, but their canine teeth did not project, so you didn't see fangs when the animal smiled, opened it's mouth, or yawned. And the males were twice the body size of the females.

"They had ape-sized brains... They had very large teeth with very thick enamel."

Alan Walker, Pennsylvania State University

While Meave Leavey's discovery was significant for the Homo sapiens species, another recent discovery has added to the overall hominid branch. A species called "ramidus" was identified last year. It goes even further back on the hominid branch of the primate family tree. This revelation came from fossils in Ethiopia that has been dated at nearly four and a half million years. But ramidus was recently reassigned to a new genus: Ardipithecus. Scientists believe it may have been a separate branch that died out, and is not a link to modern man.

So Australopithecus anamensis remain the most important recent discovery. It means an identification has been made of a hominid that existed between the time of ramidus and the age of Lucy. This bolsters the belief that several types of hominids roamed Africa as far back as four million years ago.

And scientists say more discoveries may be yet to come. There is active paleontology now being conducted in both Kenya and Ethiopia. That means right now, there is a better chance of finding a more comprehensive documentation of the critical phase between ramidus and Lucy. Such findings would further the quest to pinpoint how long ago hominids split off from apes and began the evolution towards the humans we are today.

New discovery pushes back human history

"They had ape-sized brains... They had very large teeth with very thick enamel."

Alan Walker, Pennsylvania State University

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