Saturday, October 07, 2006

hobbit debate

NY Times, May 19, 2006
Debate on Little Human Fossil Enters Major Scientific Forum


Not all scientists agree that the 18,000-year-old "little people"
fossils found on the Indonesian island of Flores should be designated
an extinct human-related species. Some expressed their opposition in
news interviews and informal symposiums, but papers arguing their case
were rejected by major journals.

Now the critics are getting their day in the court of scientific discourse.

In today's issue of the journal Science, researchers led by Robert D.
Martin of the Field Museum in Chicago present evidence they say
supports their main argument, that the skull in question is not that
of a newfound extinct species, but of a modern Homo sapiens afflicted
with microcephaly, a genetic disorder characterized by a smaller than
normal brain and head size.

The researchers said the evidence used in previous studies to rule out
microcephaly was flawed. They noted that the analysis was primarily
based on comparisons with a brain cast made from a poorly preserved
skull of a 10-year-old who was microcephalic, not one from an adult.

"Quite simply, it could not have been a worse example for such a
study," Dr. Martin, a primatologist, said in a telephone interview,
speaking of the fossil skull that was examined. "It tells us nothing
about a microcephalic that is able to survive into adulthood."

Dean Falk, an anthropologist at Florida State University, published a
study in Science last year that was said to show that the Flores
specimen's brain, though about one-third the size of a contemporary
human's, was probably organized in a way consistent with fairly
advanced behavior.

It could have been a separate species, Dr. Falk concluded, one that
was capable of making the stone tools and other technologies
associated with the discovery site.

"We stand by our original interpretation," she said yesterday by telephone.

Indonesian and Australian scientists found the fossil bones of nine
individuals of unusually small stature, little more than 3 feet, in a
cave on Flores. The principal discoverers were Michael J. Morwood, an
Australian archaeologist, and Peter Brown, also of Australia, a
paleontologist and co-leader of the team.

Announcing the discovery in 2004, the scientists concluded that the
"little people," as they are often called, were a separate human
species, which they named Homo floresiensis.

Their brain size was comparable to the Lucy specimen of
Australopithecus afarensis, a hominid species that lived up to three
million years ago. An earlier hypothesis that the species was related
to Homo erectus, an intermediate ancestor of humans, has been
generally discredited.

Almost immediately after the find, Dr. Martin and Teuku Jacob, one of
Indonesia's senior paleontologists, suggested that the one
well-preserved skull might have belonged to a relatively modern human
deformed by microcephaly. They said the braincase was too small to
result from normal dwarfing.

Moreover, James L. Phillips, an anthropologist at the University of
Illinois at Chicago and a co-author of the new journal article, said
the style and workmanship of tools found with the fossils were so
advanced "that there is no way they were made by anyone other than
Homo sapiens."

Dr. Martin complained that Dr. Falk's study had failed to compare the
Flores skull of an adult female with the dozens of forms that
microcephaly can take, particularly differences between fatal
childhood cases and those of survivors who lived to be adults. One
specimen the Falk research relied on, Dr. Martin noted, was that of a
child with one of the smallest braincases seen in a sample of more
than 100 microcephalics.

The new report, the researchers said, is based on examinations of more
microcephalic cases, two of which more closely resemble the Flores
specimen. The study, they concluded, "supports the hypothesis of
modern human microcephaly."

Dr. Martin said the journal report was a brief summary of a more
detailed manuscript that will soon be submitted for publication in The
Anatomical Record, a journal of anatomy and evolutionary biology.

In a separate paper in Science, Dr. Falk and associates, including Dr.
Morwood, disputed the importance of differences between child and
adult microcephalic cases. Dr. Falk complained that the line drawings
of microcephalic braincases in Dr. Martin's report were not
sufficiently detailed to substantiate his assertions.

"My team has just completed a big comparative study of microcephalics,
and we are confident of our original interpretation," Dr. Falk said in
an interview.

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