Human Family Tree Gets Bushy, Grows Roots

By Jill Neimark|Thursday, September 23, 2010
RELATED TAGS: HUMAN ORIGINS, NEANDERTHALS

The study of human origins has been marked by lively—sometimes vicious—sparring over the identity of the original human ancestor. The battle royal is best symbolized by world-famous Lucy, a 3.2 million-year-old fossil Australopithecus afarensis originally unearthed in 1974 and put forth as the original biped leading to us. The furor over Lucy’s pedigree embroiled researchers of the 1980s and remains unresolved, but proof could be beside the point. “I frankly do not care,” says Stony Brook paleoanthropologist William Jungers. “She allows us to understand what our precursors looked like: sexually dimorphic, small-brained bipeds retaining the ability to climb trees.”

Recent discoveries offer a deeper and broader view of human ancestry. One stunner: Early humans mated with Neanderthals, according to evolutionary geneticist Svante Pääbo and colleagues at the Max Planck Institute for Evolutionary Anthropology in Germany. Through an analysis of DNA fragments from Neanderthal bones, Pääbo traced the interbreeding back 60,000 years to the Middle East. Today 1 to 4 percent of the human genome outside Africa is Neanderthal. Another shock came last year when Tim White of the University of California, Berkeley, and the Middle Awash Team unveiled Ardipithecus ramidus (“Ardi”), a 4.4 million- year-old fossil female hominid. Bipedal on the ground but efficient at moving through trees, Ardi suggests the common ancestor we share with chimpanzees was an ape with monkeylike traits. Finally, in 2004, in a cave on the island of Flores in Indonesia, bones of a human relative no larger than a modern-day 4-year-old were discovered by archaeologist Michael Morwood of the University of Wollongong in Australia and his team. The bones are 14,000 years old, but tools nearby date back as much as a million years. After furious debate, most paleoanthropologists now agree that Homo floresiensis, nicknamed the hobbit, is a genuine ancient human with a teensy brain folded in ways that increased its complexity—enough for hobbits to hunt cooperatively, knap their own tools, and thrive on an island for more than a million years.

“We’re the last hominid standing,” Jungers says. But it is no longer clear whether we are the crown of creation or just one branch of a diverse evolutionary bush.

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