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| RichTravsky... |
 Posted: Sun Nov 01, 2009 10:41 pm |
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http://blogs.sciencemag.org/origins/2009/10/primatologists-go-ape-over-ard.html
[...]
The roughly 50-kilogram female, which the Ardipithecus team concludes walked
upright although it also spent time in the trees, has a decidedly un-chimplike
anatomy. White and colleagues therefore have asserted that living apes are not
good models for understanding the last common ancestor (LCA) of humans and
chimpanzees — a claim that has stung many primatologists. "I assumed … chimps
might be helpful in tackling the challenges of human evolution," said chimpanzee
expert William McGrew of the University of Cambridge in the United Kingdom. But
after Ardi, "all this chasing after chimpanzees was deemed to be irrelevant" to
human evolution. McGrew, the first speaker, challenged a statement in one of the
papers in Science that "no modern ape is a realistic proxy for characterizing
early hominid evolution—whether social or locomotor."
[...]
The team argues that Ardi’s anatomy suggests that its behavior and social
structure also differed from that of modern chimps. For example, one of the
papers, authored by Lovejoy, suggests that A. ramidus males were probably much
less aggressive toward each other than chimp males are and that they pair-bonded
with females.
McGrew told the attendees that although he agreed that "the LCA was not a
chimpanzee," the behavior of living chimps such as those at left can still inform
hypotheses about the LCA's behavior. McGrew listed the considerable evidence for
chimp behaviors that possibly mirror those of extinct and modern humans, such as
the use of complex tools, aiming and throwing objects, the construction of sleeping
nests or platforms, and evidence for considerable spatial cognition such as the
ability to remember the locations of thousands of trees in a forest. At least some
of these behaviors, McGrew said, are shared by chimps and modern humans because they
have deep evolutionary roots. "So to hypothetically credit the LCA with the ability
of [chimps] is not unreasonable," McGrew concluded.
At the end of the day, when the meeting was thrown open for discussion among the
roughly 200 attendees, White countered McGrew’s argument, pointing to what he saw as
the dangers of using a chimp model for the LCA's behavior. "If we try to model the
LCA or even the earliest hominids based on living chimps, which have these
adaptations to [swinging in the trees], to moving through that canopy so well and so
quickly that they can take down a red colobus monkey, we could be very misled.
Ardipithecus probably couldn't do that, and the LCA probably couldn't do that."
Yet White says he's not trying to toss out all chimp research. "The fact that a few
highly derived descendants managed to survive until today obviously enhances our
appreciation of their evolution," he told Science. "It also provides perspective on
ours. The study and conservation of chimpanzees and bonobos are surely justifiable
on their own merits, even though [early] hominid skeletal anatomy, behavior, and
ecology do not match those seen now in these specialized persistent ape lineages."
And Carol Ward, a paleoanthropologist from the University of Missouri School of
Medicine in Columbia, points out that White and Lovejoy "aren't saying that [studies
of] chimps aren’t useful but that we didn’t evolve from chimps, so they are useful
as referential models rather than actual representatives of what our ancestors were
like." Chris Stringer of the Natural History Museum in London, who co-organized the
meeting with Alan Walker of Pennsylvania State University, University Park, also
sees a role for chimp work in evolutionary studies. "There is such a lot of excellent
and important data on ape behavior," Stringer told Science, "that we would be foolish
to throw it out as providing potential models for the behavior of early hominins." |
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