Wednesday, May 6, 2009

distinct member of our ancestral family, rather than pathologically shrunken misfits

TO BE NOTED: From Wired:

Hobbits May Belong on New Branch of Our Family Tree
  • 4:08 pm |
  • Categories: Anthropology

Evidence continues to mount that Homo floresiensis, the controversial hominids better known as hobbits, were a distinct member of our ancestral family, rather than pathologically shrunken misfits.

According to analyses published Wednesday in Nature, the big toes of H. floresiensis are disproportionately longer than those of either modern humans, formally known as Homo sapiens, or Homo erectus, the original out-of-Africa hominid.

The exceptionally tiny brain of H. floresiensis, which some researchers thought could not be explained by natural evolutionary pressures, also fits with brain development seen in ancient species of hippos who evolved in island isolation, just like the hobbit.

The papers are the latest salvos in a battle that’s raged since 2003, when anthropologists found one semi-complete skeleton and fragments of six others in an Indonesian island cave. The skeletons appeared to come from hominids who stood just three feet tall and were anatomically distinct from H. sapiens.

Anthropologists who believed the fossils represented a new species named it after its home island of Flores, where local folk tales described a race of diminutive jungle dwellers. They hypothesized a direct-line descent from H. erectus, the last common ancestor of all human species, who left Africa 2.5 million years ago.

But other researchers were unconvinced. They said the hobbits’ brains were too small to have made the sophisticated stone tools found with their skeletons. The skeletons probably belonged to pathologically stunted locals who’d been ritually buried by their fully H. sapiens tribe, said the skeptics.

Since 2003, researchers on both sides of the divide have produced interpretations supporting their arguments. But as described in a recent New York Times article, “The research community is definitely trending towards the hobbits.” Richard Leakey, a preeminent anthropologist who originally refused to take sides in the debate, told the Times that recent research “greatly strengthened the possibility” that H. Floresiensis was real.

The latest studies strengthen the possibility even more. In the first, State University of New York at Stony Brook biomechanicist William Jungers reports that H. floresiensis could move its big toes from side-to-side, just like modern humans, but the toes are so disproportionately long that they resemble the toes of apes rather than our own.

This suggests that H. floresiensis may belong to an as-yet-unknown branch of the human family tree, possibly even an evolutionary brother of Homo erectus. “These new findings raise the possiblity that the ancestor of H. floresiensis was not Homo erectus but instead some other, more primitive hominin whose dispersal into southeast Asia is still undocumented,” wrote Jungers’ team.

In the second paper, Eleanor Weston and Adrian Lister of London’s Natural History Museum looked at fossil skulls from several species of long-extinct hippos that evolved into dwarfish form on the island of Madagascar. The brains of the hippos were unexpectedly small, even given the diminution of their bodies.

“Our findings … suggest that the process of dwarfism could in principle explain small brain size, a factor relevant to the interpretation of the small-brained hominin found on the island of Flores,” they wrote.

The papers raise interesting possibilities for the hobbit, writes Harvard University anthropologist Daniel Lieberman in an accompanying commentary. Perhaps it comes from a pre-H. erectus species, such as Homo habilis. Or maybe H. erectus was “more diverse and anatomically primitive than we thought.”

Lieberman suspects the latter, he wrote, “But the only way to test these and other hypotheses is to find more fossils, especially in Asia. Get out your shovels!”

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