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Thursday, June 18, 2009

Not the Third Chimp?

New Scientist reports on a "heretical" study that suggests Old Men of
the Forest are more closely related to us than we are to chimps. While
the authors acknowledge the closer genetic relationship between humans
and chimps, they suggest that DNA does not discriminate between older,
retained characteristics and newer, derived characteristics. They also
argue that human-orang relationship based on traditional taxonomic
work.

If someone has access to the paper in the Journal of Biogeography, it
might be nice to find out whether this article faithfully reports the
gist of the paper. It is reportedly still in press, so I don't know if
even subscribers have access yet.


The authors' work seems to suggest that some ancestral orangs lived in
Africa with pre-human hominids. I don't know whether the authors have
anything to say about brain size or tool use/tool making in orangs.
It'd be interesting to see whether they might suggest attributing some
early lithics to orang ancestors, either in Africa or in southern
Asia.


From the article:


"THESE days, we tend to accept without question that humans are "the
third chimpanzee". The term, coined by author Jared Diamond, refers to
the notion that our closest relatives are the two chimpanzee species -
the common chimp and the bonobo. But could we actually be "the second
orang" - more closely related to orang-utans than chimps?


"That is the controversial claim made this week by Jeffrey Schwartz of
the University of Pittsburgh in Pennsylvania and John Grehan of the
Buffalo Museum of Science in New York (Journal of Biogeography, DOI:
10.1111/j.1365-2699.2009.02141.x, in press)


"The idea flies in the face of mainstream scientific opinion, not
least a wealth of DNA evidence pointing to our close relationship to
chimps. Schwartz and Grehan do not deny the similarity between human
and chimp genomes, but argue that the DNA evidence is problematic and
that traditional taxonomy unequivocally tells us that our closest
living relatives are orang-utans.


"The researchers say the evidence of genetic similarity between humans
and chimps is problematic
Human evolution and phylogenomics researchers have so far given the
paper a rough reception. Some declined to comment on it, saying they
did not want to dignify the paper. One described it as "preposterous
nonsense" and another as "loopy".


"Others were less dismissive, though, agreeing that at least some of
the ideas were worth discussing, if only to confirm the overwhelming
evidence in favour of the orthodox view.


"The Journal of Biogeography's editors defended the decision to
publish the paper, arguing that it is the best way to subject Schwartz
and Grehan's argument to proper scientific scrutiny. Editor Robert
Whittaker told New Scientist he had done some "soul searching" but
eventually decided it was best to air the ideas.


"In the orthodox account of human origins, our species belongs to a
group of African apes that also includes chimps, bonobos and gorillas.
Chimps and bonobos are our closest living relatives, sharing a common
ancestor with us up to about 6 million years ago (see diagram). This
version of events is strongly supported by DNA evidence showing that
the human genome sequence is most similar to that of the chimp,
followed by gorillas, with orangs the least similar of the three.


"Schwartz and Grehan say that genome similarities cannot be taken as
conclusive evidence of the closeness of our evolutionary relationships
to the other great apes. In their scenario, around 13 million years
ago, an orang-like ape lived across a huge swathe of land stretching
from southern Africa to south-east Asia via southern Europe and
central Asia (see map). This population evolved into different
species, before extinctions in Europe and central Asia split the
original geographical range and left rump populations in east Africa
and south-east Asia. The African population evolved into the human
lineage while the Asian one evolved into orang-utans.


"In this scenario, the other African apes are a separate lineage that
split off from ours long before 13 million years ago, making orangs
our closest living relative and the chimps and gorillas more distant.


"This claim hinges on two contentious arguments. One is that DNA
sequence similarity is not necessarily an indicator of evolutionary
relatedness. The other is that, biologically, humans are more like
orangs than chimps."


Read the article at:


http://www.newscientist.com/article/mg20227133.800-orangutans-may-ous...


Or:


http://tinyurl.com/mj2qar


Or for the cautious:


http://preview.tinyurl.com/mj2qar


There is also an editorial supporting the Journal of Biogeography's
somewhat agonized decision to publish the paper in the first place.
The editorial is titled, "In praise of scientific heresy", and can be
read here:


http://www.newscientist.com/article/mg20227132.600-in-praise-of-scien...


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