#3: Meet Ardi, Your First Human Ancestor

A big analysis of the 4.4-million-year-old fossil shows that humans left the trees before leaving the forest and getting much smarter.

By Jill Neiman|Monday, January 25, 2010

Anthropologists are suddenly tearing up their long-held origin tale—that modern humans evolved from hunched, proto­human apes roaming the wide-open savannas of old. The discovery of a 4.4-million-year-old hominid named Ardipithecus ramidus (fondly shortened to “Ardi”) suggests that for a stretch during the early Pliocene, our ancestors instead lived in lush woodlands and walked on two feet. In fact, Ardi’s unexpected traits put to rest the whole idea of a chimplike missing link at the root of the human family tree.

Ardi and fossil bones from at least 35 other children and adults were uncovered in the Afar desert in Ethiopia by the Middle Awash research group. Toiling in volcanic ash, the group collected fossilized remains of more than 6,000 creatures ranging from antelopes to bats, as well as seeds and geologic samples.

“This gave us a series of fantastic, high-resolution snapshots across an ancient landscape—a true picture of what Ardi’s habitat was like,” says University of California at Berkeley paleoanthropologist Tim White, a codirector of the team. “It tells us that long before hominids developed tools or big brains or ranged the open savanna, they were walking upright.” The evidence suggests Ardipithecus is ancestral to the early hominid Australopithecus, widely considered a forerunner of our own genus, Homo.

White’s findings, published alongside related articles from more than 40 researchers, appeared in a special issue of Science in October. Together they present the picture of a fantastical, mosaic hominid —one with pelvis and feet adapted for walking but with a divergent big toe splayed out like those of modern apes for climbing and grasping. She had a small brain, about the size of a chimp’s but positioned more like a human’s. Most striking, Ardi’s upper canine teeth were close in size to those of modern humans. Analysis of tooth enamel suggests Ardi ate nuts, fruits, and tubers, supplemented by small mammals and bird eggs.

“How does one account for this strange creature?” White asks. In one of the other Science papers, noted biological anthropologist C. Owen Lovejoy of Kent State University speculates that pair-bonding may have been the trigger. Perhaps females began to prefer males who could walk, gather food, and carry it home, he suggests. Of course, given the contentious nature of the field, some experts insist the jury is still out on Ardi’s evolutionary role. But to White, the evidence overwhelmingly places her at “the first phase of human evolution.” Move over, Lucy. Ardi may just be the hominid find of this century.

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