jenabean

Jena's Rants
2001-07-12 17:33:16 (UTC)

Hope is at the end

On the western shore of Kenya's Lake Turkana, a team headed
by Meave Leakey and supported by the National Geographic
Society has discovered the 3.5 million-year-old fossil
remains of Kenyanthropus platyops, which is most likely a
completely new genus and species of early human ancestor.

A complete skull found in Kenya and dated at 3.5 million
years old is believed to be an entirely new species of
human ancestor.

The find suggests that eastern Africa, which at the time is
known to have been inhabited by Australopithicus afarensis,
of which the fossil "Lucy" is a representative, was
inhabited by at least two species of hominin, predecessors
of modern humans.
"It shows that our past is like that of any other mammal,"
said Meave Leakey, head of the paleontology department of
the National Museums of Kenya, in an interview with
National Geographic Today. "[We have] a very complicated,
diverse past with lots of different species; many of which
became extinct."

According to Leakey and the authors of the report, which
appears in the March 22 issue of Nature, the fossil find
points to diet-driven adaptation, in which species of
hominin evolved to take advantage of different food
sources.

Two Distinct Species

The skull of Kenyanthropus platyops was discovered in 1999
by Justus Erus, a team member. The expedition was searching
the 3.2 to 3.5 million-year-old sediments of the Lomekwi
River for contemporaries of Lucy.

Since the skull discovery, team member Christopher Kiarie
has been conducting meticulous work to establish the genus
and species of the skull, which is characterized by small
molar teeth, and a tall flat face.

"Platyops means 'flat face,'" said Leakey.

This physical description is vastly different from that of
Australopithicus afarensis, said Leakey. Lucy and her kin
had protruding faces and large teeth.

"The shape of the face clearly differentiates it from
Australopithicus afarensis and species that lived later,"
said Leakey.

According to the scientists, both tooth size and shape are
indicators of diet and the way in which a species chews its
food.

"The architecture of the face really depends on the diet
and how its jaws are working," said Leakey. "This is
significant because it means these ancestors were
inhabiting a different ecological niche."

Both Kenyanthropus platyops and Australopithicus afarensis
could have existed side by side without direct competition
for food resources, says Leakey.

Before the discovery of Kenyanthropus platyops, most
scientists believed that hominins did not develop a flat
face until approximately two million years ago.

Changing Picture of Evolution

Though the discovery seems to blur the lines of humankind's
family tree, according to Daniel Lieberman, an
anthropologist at George Washington University in
Washington, D.C., "This is part of a trend. We're getting
to know our ancestors better."

Since the 1970s, anthropologists have been uncovering
evidence that modern humans did not follow a linear
evolution in which one species evolved from the previous
species. The finds suggest that instead, numerous species
existed, and each adapted to different environments.

Multiple species of hominin had been discovered from time
periods earlier and later than Lucy and her kin, but the
fossil record showed only one ancestor for the middle
Pleiocene, approximately 3.5 million years ago, says
Lieberman.

"[Finding Kenyanthropus platyops] was what I expected,"
said Leakey. "If you look at the evolution of any other
mammal, there's usually a radiation of species and just a
few species survive. It didn't seem right that there was
only one line of evolution [for this time period]. There
should have been other species around."

Kenyanthropus platyops helps to fill in the picture of this
period of evolution, said Lieberman. It indicates that
multiple, different-looking species coexisted and filled
different ecological niches.

"We had a long and complex past," said Leakey. "And we are
the single surviving species. Our existence is not secure.
Just like everything else, we can be extinct too."




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