Hobbits again

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Finally: more bones.

Last October the world marveled at the announcement of the discovery of a new species of hominid, Homo floresiensis, in a cave called Liang Bua on the Indonesian island of Flores. One conclusion was more shocking than the next. First, this hominid stood only three feet high, earning it the nickname The Hobbit. Second, it lived as recently as 18,000 years ago, which was some 30,000 years after our own species had already been in southeast Asia for 30,000 years or more. The scientists argued that Homo floresiensis was a separate species that might have descended from Homo erectus of East Asia–which would mean that the last common ancestor of the Hobbits and us lived perhaps two million years ago.

Homo erectus fossils have been found on Flores, dating back 800,000 years. The oldest H. floresiensis bones dated back 90,000 years. The researchers suggested that during the intervening period Homo erectus on the island might have dwindled from about six feet tall to three. And despite the Hobbit’s distant relation to our own species, not to mention its small brain (a third the size of a human’s, and about the same as a chimp’s), the scientists argued that it was a clever hominid. They pointed to the stone tools in the cave and the evidence they had found of fires. Just writing about this stuff nearly a year later makes me shake my head in shock.

As I have detailed in a series of posts here, things soon went from controversial to ugly. Several scientists went on the record with skeptical reactions. They pointed out that the bones came mostly from a single individual. They proposed that this individual was a pygmy (like the ones that live today on Flores), or was born with a congenitally small head, or both. One source of friction in the debate was the fact that some researchers see in the fossil record of hominids a lot of diversity while others see little. The fossils then wound up in the possession of a rival scientist who made casts of them, apparently damaging them in the process.

For the most part, Hobbit junkies like myself have had to content ourselves with reading gossipy articles in newspapers. The Hobbit’s discoverers published a brain scan of the fossil skull in April, but otherwise nothing appeared in scientific journals either from the discoverers or their critics. Until now.

In this week’s issue of Nature, the scientists describe bones from nine individuals from the Liang Bua cave. Some of the bones–parts of the right arm and jaw–belong to an individual. Other leg bones, shoulder bones, and various bits of fingers and toes come from other levels in the cave. They were laid down in the cave over thousands of years, the youngest being just 12,000 years old–around the time when our ancestors were inventing agriculture.

The key conclusion of the paper is that these fossils look a lot like the original Hobbit bones reported last year. The new jaw, for example, has the same peculiar roots on its teeth as the old one, and both also lack a chin. If the original Hobbit was just a pathological human, the authors argue, then all of these new individuals would have to be pathological too. And the fact that these fossils span 80,000 years makes it even harder to hold the pathology argument. According to Harvard’s Daniel Lieberman this pattern refutes the aberrant dwarf argument, which now "strains credulity," as he writes in an accompany commentary.

This is not the final chapter, by any means. Robert Martin of the Field Museum in Chicago has confirmed that he is putting together a paper that will dispute the claim that the Hobbit is something other than human, and others may well be up to the same. "Regardless of one’s stand on this issue," Dr. Martin wrote to me in an email, "it is about time that the message got out that there are serious grounds for doubt about current interpretation of the Flores remains."

This a vital part of the scientific process, but the high stakes in paleoanthropology always slow it down. And the bitterness caused by the tussle over Homo floresiensis’s fossils will probably make it even harder for these precious few fossils to be shared. Still, I’m curious to see how Martin and others expand their attack from the original individual to the expanded collection of Hobbits. (I’ll update this post when I come across any interesting responses from skeptics.)

If the Hobbits hold up under this scrutiny, there are still a lot of deep questions that will have to be answered. Were Homo erectus really their ancestors, for example? Tim White, a prominent paleoanthropologist at Berkeley, has suggested that they might be descended from our own species, having undergone a radical evolutionary change into a separate species of small-brained dwarves in just tens of thousands of years. The peculiar traits of Homo floresiensis such as its teeth might make that unlikely. The Nature author meanwhile offer some evidence that might suggest they belong to an even older branch of hominid evolution that Homo erectus. Earlier hominids, dating back before Homo erectus moved out of Africa, had the same overal body proportions as Homo floresiensis, as well as a small brain. Lieberman’s skeptical on this possibility, because there are so many traits that Homo erectus and Homo floresiensis share. Still, the exodus of hominids from Africa 2 million years ago still poses a lot of puzzles; maybe different pioneers leaving Africa around the same time gave rise to the two different species. And what about all the other islands of Indonesia? Are more little bones waiting to be found on them as well?

Unfortunately, on Flores at least, these questions may be left hanging. The dispute has led to the absurd situation that the team who found the Hobbits can’t get a permit to go back to Liang Bua. You have to wonder just how wise we are as a species.

Update: 2:30 pm Greetings, visitors from the National Review. I’m not sure how the Hobbit fits in with The Corner’s political discussions, but I’m happy you’re here.

Update Friday 10/14: See my latest: a human with a Hobbit brain?