INTRODUCING ARDI: This early hominid is more than a million years older than famed Lucy and presents a wealth of new information--and speculation--about how humans first embarked on our long evolutionary journey.
J.H. MATTERNES

The first full analysis of a 4.4-million-year-old early human paints a clearer picture of what the last common ancestor of humans and chimpanzees may have looked like, which is not, after all, that much like a chimp at all. The ancient Ardipithecus ramidus ("Ardi", as the most complete female specimen is known) is described in 11 research papers published online today in Science. The prodigious research effort combines Ardi's fossils with those from many other Ar. ramidus individuals—both male and female—found near the Awash River in the Afar Rift region of Ethiopia.

Ar. ramidus, although likely millions of years more recent than the so-called missing link between chimpanzees and humans, represents "coming as close as we've ever come to that last common ancestor," Tim White of the University of California, Berkeley, one of the studies' lead authors, said in a recorded interview for Science.

Ardi is, in fact, "so rife with anatomical surprises, that no one could have imagined it without direct fossil evidence," wrote C. Owen Lovejoy, a professor of anthropology at Kent State University in Ohio, and his colleagues in a summary of one of the papers.

Among the surprises: Ardi's jaw and limbs show she was a forest-dwelling omnivore, not a fruit-eater like today's chimps or an open savanna–dweller like other early hominids. Ardi had a brain about the size of a modern chimp's relative to body size (about a third the size of a modern human's). And Ar. ramidus's foot is strikingly unlike that of a modern chimpanzee, the authors of another paper (led by Lovejoy) explain.

For a primitive cousin who likely stood at only about 120 centimeters and weighed about 50 kilograms, Ardi is likely to make a big impact in the field of paleoanthropology. For instance, Ardi's physical form also has implications for many other ancient animals, including the controversial six-million- to seven-million-year-old Sahelanthropus tchadensis, discovered in Chad in 2001. The similarities in skull size and shape among these two species now has prompted the researchers of one of the new papers (led by Gen Suwa, a professor at the University of Tokyo) to conclude that S. tchadensis was, indeed, an early hominid, rather than a female ape as others have suggested.

Slide Show: Images of Ardi

Fragile fossils
First announced 15 years ago with only scant tooth and jaw fragments, Ar. ramidus had remained a relative paleoanthropological secret amidst growing literature on other early hominids, such as the well-known Lucy, a 3.2-million-year-old Australopithecus afarensis.

For the new papers, an international team of researchers assembled and described the more than 110 pieces of Ardi's skeleton, including portions of the skull, hands, feet, arms, legs and pelvis, and those of other Ar. ramidus specimens and surrounding plants and animals.

"It's an amazing amount of material," says Carol Ward, an associate professor and integrative anatomy specialist at the University of Missouri–Columbia (M.U.). "That in itself is astonishing."

The recovery efforts themselves took some "heroic efforts," says Brian Richmond, of George Washington University's Center for the Advanced Study of Hominid Paleobiology (CASHP), in Washington, D.C. Poorly fossilized, many of the bones would crumble with a normal human touch, so they were carefully removed, cast and scanned.