Last October,
a wild discovery was announced: Researchers had uncovered a new hominid species
on a remote Indonesian island. In a large limestone cave on the island of Flores,
the researchers found a skull, jawbone, pelvis and leg bones of an adult female
hominid that they subsequently dated to about 18,000 years ago. In the flurry
that followed the Oct. 28 Nature paper, scientists speculated about whether
the diminutive hominid, referred to in the press as the “hobbit,”
was a new species or whether it was a Homo sapiens with an abnormality
— and what either conclusion might indicate about human evolution.
Researchers have compared the braincase of a new hominid find (left) to modern
humans (right), as well as to chimps and other hominids, to try to determine
if it is indeed a new species of diminutive hominid that lived 18,000 years
ago. Image courtesy of Peter Brown.
By studying the hominid’s relatively small skull and models of its brain,
paleoanthropologist Dean Falk of Florida State University in Tallahassee and
colleagues decided that this human is indeed a new species, Homo floresiensis,
as described in the March 3 Science Express. The team made several 3-D
models of the cranial cavity and compared the brain size and structure to those
of other animals, including other hominids, chimpanzees and modern humans with
microcephaly, a condition involving an unusually small head and mental defects.
Because the skull and bones are extremely fragile, Falk says, the scientists
who discovered the H. floresiensis skeleton sent Falk and colleagues
a model of the skull based on a CAT scan. From that model, Falk, who has been
studying primate brains for 30 years, and her co-workers created a virtual model
and a rubber latex model, called an endocast, of the cranial cavity that shows
the approximate shape of the brain. “Brains leave an imprint in the braincase,”
Falk says, and with the endocasts, “we were able to ‘see’ blood
vessels, sutures where the bones of the skull knit together, the brain shape
and size.”
The brain size of this H. floresiensis female was about 417 cubic centimeters
— about one-third of the average brain size of modern humans, Falk says.
The brain size is actually about the same as that of the famed Lucy, an Australopithecus
afarensis. But the brain shape of H. floresiensis is quite different
from Lucy’s and is actually most like that of Homo erectus, the
first species of the genus Homo, Falk says; the shape least resembles
that of modern people with microcephaly.
H. floresiensis has brain features “far advanced” for her size,
Falk says, such as two large swellings in the frontal lobe (the area of the
brain that is important for activities like planning ahead and taking initiative),
but a brain size that is “very primitive.” Quite simply, she says,
“I’ve never seen anything like this.”
Ralph Holloway of Columbia University in New York City is “not convinced”
that H. floresiensis is a new species rather than a H. sapiens
with a different type of brain abnormality, such as another variation of microcephaly.
In examining an endocast of H. floresiensis, Holloway says he hasn’t
seen the same features on the brain that Falk’s team described, noting
that any oddities could be “normal” variability. He also measured
the hominid’s brain at only 387 cubic centimeters. It could easily be a
new species, Holloway says, but “not enough comparison has been done yet.”
“The bottom line is that until we see a second or a third skull, we’re
not going to know what the thing is,” says Richard Klein, a paleoanthropologist
at Stanford University in Palo Alto, Calif. The cave where H. floresiensis
was found has apparently provided modern human skeletal remains in the past,
he says, and it would be interesting to know how they relate stratigraphically.
The parts ascribed to H. floresiensis, he says, are odd: The body is
small, the arms are too long, the teeth are too big, and the head is too small.
“Finding one body such as this one might indicate an abnormal modern human,”
Klein says. But “finding two would greatly strengthen the case that we’re
dealing with a separate human species, and finding three or more would be the
clincher.”
Any future finds, however, are “not going to upset the applecart of human
evolution,” Holloway says. “We have long known that there must have
been other hominids out there,” Klein adds.
Peter Brown, a paleoanthropologist at the University of New England in Armidale,
Australia, who was part of the original discovery and research team, says that
the team has been back in Indonesia, looking for more examples and evidence
of the miniature hominid and have found remains of at least eight H. floresiensis
individuals. When analyzing the specimens, however, Brown cautions that it is
the combination of traits, not a single trait such as brain size, that can elucidate
a specimen’s identity.
Megan Sever
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