Sasquatch Chronicles Blog

Nearly 17 years after plucking the fossilized tooth of a new human ancestor from a pebbly desert in Ethiopia, an international team of scientists today (Thursday, Oct. 1) announced their reconstruction of a partial skeleton of the hominid, Ardipithecus ramidus, which they say revolutionizes our understanding of the earliest phase of human evolution.

The female skeleton, nicknamed Ardi, is 4.4 million years old, 1.2 million years older than the skeleton of Lucy, or Australopithecus afarensis, the most famous and, until now, the earliest hominid skeleton ever found. Hominids are all fossil species closer to modern humans than to chimps and bonobos, which are our closest living relatives.

“This is the oldest hominid skeleton on Earth,” said Tim White, University of California, Berkeley, professor of integrative biology and one of the co-directors of the Middle Awash Project, a team of 70 scientists that reconstructed the skeleton and other fossils found with it. “This is the most detailed snapshot we have of one of the earliest hominids and of what Africa was like 4.4 million years ago.”

White and the team will publish the results of their analysis in 11 papers in the Oct. 2 issue of the journal Science, which has Ardi on the cover. They announced their findings at press conferences held simultaneously today in Washington, D.C., and Addis Ababa, Ethiopia.

The team’s reconstruction of the 4-foot-tall skeleton and of Ardi’s environment — a woodland replete with parrots, monkeys, bears, rhinos, elephants and antelope — alters the picture scientists have had of the first hominid to arise after the hominid line that would eventually lead to humans split about 6 million years ago from the line that led to living chimpanzees.

Based on a thorough analysis of the creature’s foot, leg and pelvis bones, for example, the scientists concluded that Ardi was bipedal — she walked on two legs — despite being flat-footed and likely unable to walk or run for long distances.

In part, this primitive ability to walk upright is because Ardi was still a tree-dweller, they said. She had an opposable big toe, like chimpanzees, but was probably not as agile in the trees as a chimp. Unlike chimps, however, she could have carried things while walking upright on the ground, and would have been able to manipulate objects better than a chimp. And, contrary to what many scientists have thought, Ardi did not walk on her knuckles, White said.

Ardi was not a chimpanzee, but she wasn’t human,” stressed White, who directs UC Berkeley’s Human Evolution Research Center. “When climbing on all fours, she did not walk on her knuckles, like a chimp or gorilla, but on her palms. No ape today walks on its palms.”

Ardi’s successor, Lucy, was much better adapted for walking on the ground, suggesting that “hominids became fundamentally terrestrial only at the Australopithecus stage of evolution,” he said.

Based on Ardi’s small, blunt, upper canine teeth, the team also argues that the males of that species did not engage in the same fearsome, teeth-baring threat behavior common in chimpanzees, gorillas and orangutans. Instead, they must have had a more amicable relationship, the scientists said, implying that several pair-bonded couples lived together in social units. Males may even have helped in gathering food for sharing.

“The novel anatomy that we describe in these papers fundamentally alters our understanding of human origins and early evolution,” said anatomist and evolutionary biologist C. Owen Lovejoy of Kent State University, a scientist with the project. In a summary article in Science, Lovejoy wrote that these and other behaviors “would have substantially intensified male parental investment — a breakthrough adaptation with anatomical, behavioral, and physiological consequences for early hominids and for all of their descendants, including ourselves.”