Australopithecus sediba‘s skull. Photo by Brett Eloff, courtesy of Lee Berger and the University of Witwatersrand
The world’s leading paleoanthropologists announced the discovery of the most extensive set of prehuman remains this week. The bones — partial skeletons of a an adult male and female, a juvenile and several infants — all come from a never-before-seen hominid species that they’re calling Australopithecus sediba. “It is hugely significant,” Ian Tattersall, a paleoanthropologist at the American Museum of Natural History, told The Wall Street Journal. “This is a good example of what we see throughout the human fossil record — vigorous experimentation with species thrown out to succeed or fail.”
The skeletons have slim, sloped shoulders and long arms (good for tree-swinging!) like a chimpanzee, but they have delicate hands like a human. The ribs are ape-like up top but human-like further down. The species likely walked upright, but not as gracefully as we do. The gait is more of a shuffle than a stride, and the hominid was probably pigeon-toed. The remains were actually discovered back in 2008 in South Africa, but after five years of poring over the details, only now are scientists ready to draw conclusions about how A. sediba moved, which they’ve discussed in six separate papers published this week in Science.
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A. sediba‘s arms appear designed for climbing, while the shape of its ribcage would have made its arms difficult to swing while walking. Yet it likely did shuffle upright, which would—in locomotive terms, at least—make it fit in somewhere between apes and early Homo species.
That finding marks a milestone in the search for origin of the human species that’s quite possibly as significant as the recently discovered human-neanderthal love child or the 3.2 million year-old Australopithecus afarensis remains better known as Lucy, or even the famed Java Man (Homo erectus erectus), the first set of remains ever to show traits from both humans and apes.
A. sediba, with an adult Homo sapiens female on the left and
a male chimpanzee on the right.
Credit: Lee Berger; University of the Witwatersrand
In pop science, any one of these discoveries could be considered a “missing link,” the popular, if perhaps misleading, term for a transitional fossil that shows how an early human ancestor bridged the gap between ape and man.
Pop science is not real science. In the past century or so, the evolutionary debate has been muddled with this idea that we should be able to connect the Homo sapien species with an ape-like ancestor that’s directly connected to a more primitive life form and so on and so on until we get back to the primordial sludge from which all life apparently originated.
The media loves this idea of a missing link because it implies that the mystery of human evolution is a question that has a single answer. That’s hardly the case, as even A. sediba shows, because human evolution can’t be traced back down a single lineage; species split off, evolved, separated, died out, and so on.
What we’ve learned since the days of Darwin is that the chain of evolution isn’t exactly a chain. It’s more of a web. And while Creationists love to point out that scientists have yet to identify the missing link, meaning the Darwinian theory of evolution must be flawed, many scientists now shy away from this “missing link” idea altogether. So to answer our own headline, this new half-chimp half-human is not the missing link, because there’s basically no way to identify a species specifically as a missing link.
The evolution of mankind as we know it happened over the course of millions of years and includes lots of false starts and dead ends. As our human-Neanderthal love child taught us, too, there was likely a decent amount of interbreeding along the way. So, it wasn’t like one superior species pushed an inferior species into extinction, pushing the evolutionary ball forward. The different early human species overlapped and interbred and went extinct and survived. Scientists don’t expect to arrive at a eureka moment that provides them with all the answers. Instead, figuring out our ancestry will take lots of effort to continue finding new, informative pieces of the fossil record, like this one.
