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Science Magazine: Australopithecus sediba “Ousted from the Human Family”


A few years ago we wrote about Australopithecus sediba, a hominid fossil that was discovered in South Africa in 2008. There was a lot of hype about this hominid when it was first published in 2010. Its discoverer, Lee Berger, called sediba “possibly the best candidate ancestor for our genus.”

The original hope for sediba is that it would help fill a “gap” in the fossil record that pertains to the precise time when evolutionary paleoanthropologists believe our genus Homo evolved from some australopithecine ancestor. ABC News made this point when sediba was first announced, calling the fossil a “game-changer”:

Scientists have long talked about a “missing link” between very old fossils, more than 3 million years old, and much newer ones that they believe are clearly ancestors of today’s human beings. There is a gap in the fossil record, so far unexplained. Does Australopithecus sediba help fill the gap? Not on its own, say most researchers, but it helps.

The media touted sediba as a spectacular confirmation of this prediction. The Washington Post ran the headline, “Scientists identify ancestor that bridges gap in human evolution, a potential ‘game-changer,’” while the Associated Press quoted paleoanthropologist Darryl J. DeRuiter, stating:

This is what evolutionary theory would predict, this mixture of Australopithecene and Homo … It’s strong confirmation of evolutionary theory.

Now, things have changed radically. As the journal Science reports, “A famous ‘ancestor’ may be ousted from the human family,” explaining that Australopithecus sediba is far removed from the human portion of the hominid tree:


This isn’t exactly anything new. The article makes another point we’ve made here at Evolution News in the past, namely that “With its fossils dated to 1.98 million years ago, Au. sediba is too young to be directly ancestral to all members of the genus Homo.” However, this new study doesn’t argue against sediba as a human ancestor simply because the age of the species is wrong, but also on the basis of the fossil’s morphology:




Those are some very big names who think that Au. sediba is merely an extinct side-branch of the hominid tree and not ancestral to Homo. So much for sediba being a human ancestor who is “what evolutionary theory would predict.”

But if not Au. sediba, from what did our genus Homo evolve? When Au. sediba was first reported, the science media admitted that we simply don’t know:

The oldest Homo specimens are scrappy and enigmatic, leaving researchers unsure about the evolutionary steps between the australopithecines and Homo. … “The transition to Homo continues to be almost totally confusing,” says paleoanthropologist Donald Johanson of ASU Tempe, who has seen the new fossils.

(Michael Balter, “Candidate Human Ancestor From South Africa Sparks Praise and Debate,” Science, Vol. 328:154-155 (April 9, 2010).)

With the fall of Australopithecus sediba, that confession of ignorance seems to be left firmly in place.

Photo credit: Brett Eloff/Courtesy Profberger and Wits University (Own work) [GFDL or CC BY-SA 4.0-3.0-2.5-2.0-1.0], via Wikimedia Commons.