[2005/09/01] Chimpanzee Fossil Upsets Early Man Speciation Theory
Chimpanzee Fossil Upsets Early Man Speciation Theory 09/01/2005 Paleontologists need no longer lament the complete dearth
of chimpanzee fossils. Nature announced the discovery of the
first fossil chimpanzee teeth. The location, however – the Great
Rift Valley in Africa – was unexpected. The discoverers, Sally
McBrearty and Nina G. Jablonski,1 explain:
There are thousands of fossils of hominins,
but no fossil chimpanzee has yet been reported. The chimpanzee
(Pan) is the closest living relative to humans [sic].
Chimpanzee populations today are confined to wooded West and central
Africa, whereas most hominin fossil sites occur in the semi-arid East
African Rift Valley. This situation has fuelled speculation
regarding causes for the divergence of the human and chimpanzee
lineages five to eight million years ago [sic]. Some
investigators have invoked a shift from wooded to savannah
vegetation in East Africa, driven by climate change, to explain
the apparent separation between chimpanzee and human ancestral
populations and the origin of the unique hominin locomotor
adaptation, bipedalism. The Rift Valley itself functions as an
obstacle to chimpanzee occupation in some scenarios.
Here we report the first fossil chimpanzee. These fossils,
from the Kapthurin Formation, Kenya, show that representatives of
Pan were present in the East African Rift Valley during the
Middle Pleistocene, where they were contemporary with an extinct
species [sic] of Homo. Habitats suitable for both
hominins and chimpanzees were clearly present there during this period,
and the Rift Valley did not present an impenetrable barrier to
chimpanzee occupation. (Emphasis added in all
quotes.)
The teeth, estimated by radiometric methods to be
around 500,000 years old, were found within 1 kilometer of a hominid
fossil site. This should not be surprising, since scientists believe
chimpanzees ranged over a much wider area than the past; their restricted
habitats today are due partly to pressure from human occupation. The
area where the three chimp teeth were found has revealed fossils of many
other large and small mammals, including monkeys. The authors
explain what this means to evolutionary theory:
This evidence shows that in the past
chimpanzees occupied regions in which the only hominoid inhabitants
were thought to have been members of the human lineage. Now
that chimpanzees are known to form a component of the Middle
Pleistocene fauna in the Rift Valley, it is quite possible that they
remain to be recognized in other portions of the fossil record
there, and that chimpanzees and hominins have been sympatric since
the time of their divergence.
By sympatric, they
mean that the lineages diverged in proximity, without being geographically
isolated (allopatric). Sympatric speciation was until recently
viewed as heretical; now, paleoanthropologists will have to come up with new ideas for
why humans diverged from the great apes, given that they apparently shared
the same habitat. See also http://www.nature.com/news/2005/050829/full/050829-10.html,
BBC News,
and MSNBC News.
1McBrearty and Jablonski, ¡°First fossil
chimpanzee,¡± Nature
437, 105-108 (1 September 2005) | doi: 10.1038/nature04008.
Part of the reason none have been found
in this area before is that paleoanthropologists were not looking for
them. McBrearty said that now we know they are there, researchers
¡°will start looking for them,¡± implying that the favorite story
of human divergence through migration to the grasslands blinded their
eyes to the possible presence of chimpanzee fossils in the Great Rift
Valley. Since this was the hotbed of hominid bones that made the
Leakeys famous, hunters wanted missing links, not existing species of
chimpanzees. This announcement will not frustrate
Darwinists very much. They actually enjoy new twists to the plot
of their favorite story. Maybe some will say the Homo
neighbors brought the chimp back from a hunt in the jungle and had it
for dinner, spitting out the teeth. Most likely this will give a
temporary boost to the internecine heresy of sympatric speciation, but
it will be harder to come up with a reason why Pan and
Homo diverged so much if they lived in the same vicinity.
Maybe it will also revive the simplistic Larry King question, ¡°If we
evolved from apes, why are there still apes?¡± The answer is, of
course, that some of them had a choice. Sharp minds
will notice that there is no evolutionary evidence here. The
Homo fossils were described in the BBC piece as ¡°probably¡± an
advanced form of Homo erectus, whatever that vague category means. They ¡°looked like people and were a fairly sophisticated
culture with various stone tools and lived in the same environment as
humans.¡± If they looked like people and and acted like people, why
even differentiate them from people? There are Homo sapiens
sapiens today that share that same habitat and match that same
description right now. People come in a variety of sizes and
shapes, but are all one species of people. What¡¯s evolution got to
do with it?