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 our
|Contact: Robert Sanders|
University of California - Berkeley