[Apologetics] Surprising fossils throw kink in human evolution theory

[Art Kelly]

Aug. 8, 2007, 2:00PM
African fossils paint messy picture of human evolution
http://chron.com/disp/story.mpl/front/5037321.html
 
WASHINGTON — Surprising fossils dug up in Africa are
creating messy kinks in the iconic straight line of
human evolution with its knuckle-dragging ape and
briefcase-carrying man.

The new research by famed paleonoloigst Maeve Leakey
in Kenya shows our family tree is more like a wayward
bush with stubby branches, calling into question the
evolution of our ancestors.

The old theory was that the first and oldest species
in our family tree, Homo habilis, evolved into Homo
erectus, which then became us, Homo sapiens. But those
two earlier species lived side-by-side about 1.5
million years ago in parts of Kenya for at least half
a million years, Leakey and colleagues report in a
paper published in Thursday's journal Nature.

In 2000 Leakey found an old H. erectus complete skull
within walking distance of an upper jaw of the H.
habilis, and both dated from the same general time
period. That makes it unlikely that H. erectus evolved
from H. habilis, researchers said.

It's the equivalent of finding that your grandmother
and great-grandmother were sisters rather than
mother-daughter, said study co-author Fred Spoor, a
professor of evolutionary anatomy at the University
College in London.

The two species lived near each other, but probably
didn't interact with each other, each having their own
"ecological niche," Spoor said. Homo habilis was
likely more vegetarian and Homo erectus ate some meat,
he said. Like chimps and apes, "they'd just avoid each
other, they don't feel comfortable in each other's
company," he said.

They have some still-undiscovered common ancestor that
probably lived 2 million to 3 million years ago, a
time that has not left much fossil record, Spoor said.

Overall what it paints for human evolution is a
"chaotic kind of looking evolutionary tree rather than
this heroic march that you see with the cartoons of an
early ancestor evolving into some intermediate and
eventually unto us," Spoor said in a phone interview
from a field office of the Koobi Fora Research Project
in northern Kenya.

That old evolutionary cartoon, while popular with the
general public, keeps getting proven wrong and too
simple, said Bill Kimbel, who praised the latest
findings. He is science director of the Institute of
Human Origins at Arizona State University and wasn't
involved in the research team.

"The more we know, the more complex the story gets,"
he said. Scientists used to think H. sapiens evolved
from Neanderthals, he said, but now know that both
species lived during the same time period and that we
did not come from Neanderthals.

Now a similar discovery applies further back in time.

Leakey's team spent seven years analyzing the fossils
before announcing their findings that it was time to
redraw the family tree — and rethink other ideas about
human evolutionary history, especially about our most
immediate ancestor, H. erectus.

Because the H. erectus skull Leakey recovered was much
smaller than others, scientists had to first prove
that it was erectus and not another species nor a
genetic freak. The jaw, probably from an 18- or
19-year-old female, was adult and showed no signs of
any type of malformations or genetic mutations, Spoor
said. The scientists also know it isn't H. habilis
from several distinct features on the jaw.

That caused researchers to re-examine the 30 other
erectus skulls they have and the dozens of partial
fossils. They realized that the females of that
species are much smaller than the males — something
different from modern man, but similar to other
animals, said study co-author Susan Anton, a New York
University anthropologist. Scientists hadn't looked
carefully enough before to see that there was a
distinct difference in males and females.

Difference in size between males and females seem to
be related to monogamy, the researchers said. Primate
species that have same-sized males and females, such
as gibbons, tend to be more monogamous. Species that
are not monogamous, such as gorillas and baboons, have
much bigger males.

This suggests that our ancestor H. erectus reproduced
with multiple partners.

The H. habilis jaw was dated at 1.44 million years
ago. That is the youngest ever found from a species
that scientists originally figured died off somewhere
between 1.7 and 2 million years ago, Spoor said. It
enabled scientists to say that H. erectus and H.
habilis lived at the same time.

All the changes to human evolutionary thought should
not be considered a weakness in the theory of
evolution, Kimbel said. Rather, those are the
predictable results of getting more evidence, asking
smarter questions and forming better theories, he
said.



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