The Family From 2 Million B.C.

Are fossils from a South African cave the leading candidate for the title of “direct ancestors of humans”?

By KELLI LEVEY

Call these fossilized humanoids mysterious. Call them mesmerizing. But don’t call them the missing link in human evolution.

Image by Brett Eloff, courtesy of Wits UniversityThe phrase is antiquated, Texas A&M University anthropologist Darryl de Ruiter says, and hardly worthy of the collection of fossils that could be “the best candidate for a direct ancestor of humans.”

The fossils are estimated to be between 1.78 million and 1.95 million years old; they were discovered in August 2008, in a remote cave outside Johannesburg, South Africa. They are “extremely complete and extremely well-preserved,” de Ruiter says.

His scientific team used GPS and GIS (Geographic Information System) data to find the cave, which is 10 feet wide, 10 feet high and about 8 feet deep. The team leader’s nine-year-old son found the first bone.

The researchers describe their findings in the cover story of the April 9, 2010 issue of Science—the official journal of the American Association for the Advancement of Science—titled “Australopithecus sediba: A New Species of Homo-Like Australopith from South Africa.” The lead author is project director Lee Berger of the University of the Witwatersrand; de Ruiter, the lead craniodental specialist on the project, is the second author.

De Ruiter described the findings during a departmental lecture about two weeks after the report was released. “Anything I’ve shown you so far is spectacular on its own, but to think about what it represents—that is what is truly spectacular,” he told the group. “We have an australopith with Homo tendencies. They have long arms with fingers almost to their knees, and massive upper-arm strength. These are characteristics of australopiths; then there are characteristics of the cranium and the pelvis that are derived toward Homo.”

The fossils the team found first are from an adult female and a juvenile male. Since the article was released, additional skeletons have been discovered, including the remains of a baby (aged three to six months) and an adult male, de Ruiter adds.

The genus name Australopithecus means “southern ape,” and the species is loosely referred to as an “ape man” because it could easily navigate in the trees but, once on the ground, could walk on two legs as humans do, de Ruiter explains. “Sediba” means “fountain” or “wellspring” in the Sesotho language.

He points to a photo of the female and the young male. “Our working hypothesis is that this is Mommy, this is Son and any others we find were closely related,” he explains.

He theorizes that the family died when the cave collapsed. The placement of the skeletons and the lack of tooth marks, despite the discovery of animal remains nearby, support that theory. De Ruiter says he expects the team to find additional skeletons in the cave walls as they continue painstakingly unveiling the findings—removing the lichen and mold with hand-held air guns. About 18,000 hours already have been devoted to the process, and most of the researchers, including de Ruiter, plan to return over the summer months.

Only three other skeletons this old in Africa approach this level of completeness, de Ruiter says: the 2.9-million-year-old “Lucy” from Ethiopia, the 2.2-million-year-old “Little Foot” from elsewhere in South Africa, and the 1.6-million-year-old “Nariokotome Boy” in Kenya.

De Ruiter says he expects the discovery will also attract the curious from around the world to the site in the middle of a nature preserve, and he and the other scientists hope to find other ways to make sure their research finds its way into the hands of the curious.

“The casts are cheap to make and durable, so our goal is to have these in museums and schools all around the world,” he says. “We want everyone to learn about them and be able to touch this new phase of history.”

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