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Australopithecus sediba: The Hype-Cycle Starts Again

Casey Luskin

The hyping of alleged human ancestors, fossils whose claim to fame invariably turns out later to be disproved by the evidence, has a long and undistinguished history. The trail of fallen ancestors brings us to the present day, September 2011, when the media has started a new cycle of hype with Australopithecus sediba. If history is a guide, within months or a few years we should expect to see cooler heads prevail in their analyses of this fossil. For now, though, what exactly can we make of Au. sediba?

Well for one thing, its age is about 1.98 million years, meaning that it appears after fossil evidence belonging to members of our own genus. In other words, known specimens of this species can’t be ancestral to humans because they lived after our own genus, Homo, already existed. The Los Angeles Times noted this in a comment buried deep in the article:

But the age of the fossils presents a problem. The researchers’ isotopic and magnetic dating showed the fossils were 1.977 million years old, about 300,000 years younger than a Homo habilis fossil that should have been their junior.

This is not an observation made by reporters who don’t understand evolution. Donald Johanson, for one, reportedly is convinced that since Au. sediba appears long after the appearance of Homo, it can’t be an ancestor of humans:

Dr. Johanson said in an e-mail that the Hadar jawbone “possesses all the hallmarks of Homo,” the human lineage, and “places the origins of Homo firmly in eastern Africa, at least 400,000 years prior to the dating of Au. sediba.”

The influential paleoanthropologist Fred Spoor concurs:

But other researchers have long accepted that jaw, which means that these skeletons of Au. sediba could not themselves have given rise to Homo, says paleoanthropologist Fred Spoor of University College London and the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.

(Ann Gibbons, “Skeletons Present an Exquisite Paleo-Puzzle,” Science, Vol. 333:1370-1372 (September 9, 2011).)

Meanwhile, we’re seeing the customary retroactive confessions of ignorance that typically accompany announcements about new so-called transitional fossils. By that I mean confessions that prior to a given discovery, we really didn’t understand some alleged evolutionary transition. It’s only after a supposed “transitional fossil” is discovered that evolutionists feel comfortable admitting to such “gaps” in the fossil record. This makes you wonder: what gaps exist right now that we aren’t being told about?

The journal Science published such a confession when first reporting on the Au. sediba fossils last year:

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).)

In a striking statement, Science admitted: “Our genus Homo is thought to have evolved a little more than 2 million years ago from the earlier hominid Australopithecus. But there are few fossils that provide detailed information on this transition.”

Science again acknowledged the gap in its most recent coverage of this species, stating that the Au. sediba specimens “lived just after a significant gap in the fossil record 3 million to 2 million years ago.” The article further explains the problem:

Homo first shows its face, in the form of an upper jaw also from Hadar, about 2.3 million years ago. But what came between Lucy, dated to about 3.2 million years ago, and early Homo?

One cannot help but notice that if these Au. sediba specimens lived “after” the gap, then the gap still exists.

ABC News had a recent story that made a retroactive confession of ignorance about the “gap in the fossil evidence” pertaining to the evolution of human beings:

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.

Perhaps the Washington Post should rethink its headline “Scientists identify ancestor that bridges gap in human evolution, a potential ‘game-changer.'”

The aforementioned ABC News story shows that despite the hype, many scientists aren’t accepting Au. sediba as a human ancestor:

“The team says the new species may be the best candidate yet for the immediate ancestor of our genus, Homo,” wrote Michael Balter of the Science staff in an overview piece. “That last claim is a big one, and few scientists are ready to believe it themselves just yet.”

One of those scientists is Bernard wood who said:

Dr. Wood said that although he had read the five papers quickly “late at night over a glass of whisky,” he believed they would prove to be “a watershed in our understanding of human evolution, even if only to demonstrate that things are pretty complex, and because of this it will be very difficult to link different fossils in an evolutionary sequence.”

Another scientist, Ian Tattersall, has resigned himself to accepting that we’ll never find fossil evidence of the “leap to humans” because it happened “very suddenly”:

Both Dr. Wood and Dr. Tattersall see Dr. Berger’s discovery as pointing to the great variety of australopithecine apes, from which it will be very difficult to select the particular species that gave rise to humans. Dr. Tattersall believes the leap to humans may have been brought about very suddenly, perhaps by a few critical genetic changes, which is why the transition is so hard to trace in the fossil record.

Tim White said in Science in 2010 that “Given its late age and Australopithecus-grade anatomy, it contributes little to the understanding of the origin of genus Homo.” He further noted:

The characteristics shared by A. sediba and Homo are few and could be due to normal variation among australopithecines or because of the boy’s juvenile status, argues Tim White, a paleoanthropologist at the University of California, Berkeley.

Time further reported:

Tim White, a paleontologist at the University of California, Berkeley, whose team recently discovered a 4.4 million-year-old skeleton of Ardipithecus ramidus, also believes Au. Sediba bears no relationship to modern humans. White points out that drawing strong conclusions about a species based on such a young individual as the fossilized boy is risky, because the skeleton would have still been developing. “The obsession with Homo in their [paper’s] title and text is difficult to understand outside of a media context”

So leading paleoanthropologists like Bernard Wood, Donald Johanson, Fred Spoor, Ian Tattersall, and Tim White aren’t convinced that Au. sediba was a human ancestor, but the media believes it’s perfectly acceptable to promote the opposite view to the public.

(This article has been updated.)

Casey Luskin

Associate Director, Center for Science and Culture
Casey Luskin is a geologist and an attorney with graduate degrees in science and law, giving him expertise in both the scientific and legal dimensions of the debate over evolution. He earned his PhD in Geology from the University of Johannesburg, and BS and MS degrees in Earth Sciences from the University of California, San Diego, where he studied evolution extensively at both the graduate and undergraduate levels. His law degree is from the University of San Diego, where he focused his studies on First Amendment law, education law, and environmental law.



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