Dispatches from the Culture Wars

Seth Borenstein, the AP writer, follows the template perfectly but gets almost everything wrong from the very first paragraph:

Surprising research based on two African fossils suggests our family tree is more like a wayward bush with stubby branches, challenging what had been common thinking on how early humans evolved.

Challenging what had been common thinking when, exactly? Anthropologists have known for decades that there was no simple linear progression from apes to man but rather, like virtually all evolutionary lineages, there were many sidelines that died out.

The discovery by Meave Leakey, a member of a famous family of paleontologists, shows that two species of early human ancestors lived at the same time in Kenya. That pokes holes in the chief theory of man's early evolution -- that one of those species evolved from the other...

The old theory is that the first and oldest species in our family tree, Homo habilis, evolved into Homo erectus, which then became human, Homo sapiens. But Leakey's find suggests those two earlier species lived side-by-side about 1.5 million years ago in parts of Kenya for at least half a million years.

Complete and utter nonsense. How in the world does someone get a job as a science writer for a major media outlet and not understand the incredibly basic concept that ancestral and daughter species can - indeed in most cases must - coexist, often for relatively long periods of time? Did his parents die the day he was born? Of course not. And new species can split off from an ancestral species without that ancestral species immediately dying out. This is an elementary-level mistake made by creationists all the time. An AP science writer should damn well know better; if he doesn't, he sure as hell shouldn't be writing about science.

Unfortunately, we can't put all the blame no the reporters for this; some blame also has to be given to a couple of the authors of this paper who appear to be speaking far more loosely to the media than to their fellow scientists, claiming much more in interviews in the popular media than they claim in Nature (and I only say "appear to be" because it has also often been the case that reporters have misquoted scientists or removed things from much more nuanced context, which is certainly possible in this case). But some of the quotes from a couple of the paper's authors appear to be seriously overclaiming both the strength of their findings and their importance for the larger issue of hominid evolution. Like this?

It's the equivalent of finding that your grandmother and great-grandmother were sisters rather than mother-daughter, said study co-author Fred Spoor, a professor of evolutionary anatomy at the University College in London.

The two species lived near each other, but probably didn't interact, each having its own "ecological niche," Spoor said. Homo habilis was likely more vegetarian while Homo erectus ate some meat, he said. Like chimps and apes, "they'd just avoid each other, they don't feel comfortable in each other's company," he said.

There remains some still-undiscovered common ancestor that probably lived 2 million to 3 million years ago, a time that has not left much fossil record, Spoor said.

Overall what it paints for human evolution is a "chaotic kind of looking evolutionary tree rather than this heroic march that you see with the cartoons of an early ancestor evolving into some intermediate and eventually unto us," Spoor said in a phone interview from a field office of the Koobi Fora Research Project in northern Kenya.

But that cartoon was never meant to illustrate the full story of hominid evolution, for crying out loud, it was only intended to show the basic morphological path taken by evolution. I doubt Spoor can name an anthropologist in the last few decades who actually thought such a cartoon told the full story of hominid evolution. If the best way you can sell your find is to claim that it disproves a cartoon, you're really straining for media attention for what is really just a mildly interesting find.

Even worse is this statement from another of the authors of the study in the Reuters article:

The fossils, discovered in east Africa's Rift Valley, regarded as the "cradle of humankind", challenge the idea that human prototypes evolved one after the other in a linear fashion from Homo habilis to Homo erectus, ending with modern humans.

This means they must have co-existed in different habitats at the same time, the scientists added.

"They were kind of sisters, if you like," said Frederick Manthi, the scientist who discovered the fossils. "Homo habilis never gave rise to Homo erectus. These discoveries have completely changed the story."

No, they haven't. The fact that the two species overlapped and co-existed for a time does not show any such thing. It might mean that they both evolved from a common ancestor we have not found yet (or from one of the various australopithecene species we've already found), or it might only mean that Homo erectus split off from Homo habilis and it took half a million years before Homo habilis died out or was overtaken by the daughter species.

Interestingly, he only makes such a bold claim in a popular media report. In the actual article in Nature, they're much more circumspect (as they should be):

As the earliest secure evidence of Homo is found outside the known region of overlap, it is nonetheless possible that H. erectus evolved from H. habilis elsewhere, and that the Turkana basin was a region of secondary contact between the two hominin taxa.

This looks to me like a case of a couple of scientists overclaiming the nature of their finds in the popular media to get attention, and the popular media using writers who don't know enough to catch them at it. It's a mildly interesting paper. It gives us new information about sexual dimorphism in our hominid ancestors and that's certainly useful in helping flesh out other hypotheses on human evolution. But it does not overthrow everything we know about human evolution, nor does it even require a significant change in those explanations.

At most, it means that Homo habilis and Homo erectus shared a common ancestor that we have not yet found; that would hardly be a shock. That is, in fact, quite a routine situation in paleontology. For more information, see this post by anthropologist John Hawks. He notes that even the identification of KNM-ER 42703 as habilis might not be accurate:

If they are right, it re-establishes the status quo: Homo habilis hung on after the evolution of early Homo erectus, the two species being radically different in their body size (and presumably life history) adaptation, but somehow both making tools and surviving on the same foods.

And yet, this "H. habilis" specimen, KNM-ER 42703, is nearly 200,000 years later than any other member of its species. Almost the only things that makes it H. habilis are its third molars. Are they enough? Or is it Homo erectus, too? Is the overlap completely gone, or will this fossil save it?

Again, it's an interesting find. It has bearing on several hypotheses about human evolution. But the claim that it throws out the whole story is just plain bullshit. It does nothing of the sort. And it does not serve the cause of science to have scientists issuing PR-driven exaggerations of the importance of their finds or to have reporters who don't understand the science writing it up for public consumption. Here's what it really shows: it shows that when media outlets need an article about a recent scientific discovery, they should call Carl Zimmer - and no one else.