Re: AAT reply from Elaine Morgan
Phil Nicholls (pn8886@csc.albany.edu)
31 Dec 1994 07:07:28 GMT
In article <3e2g0l$ru3@newsbf02.news.aol.com>,
Pat Dooley <patdooley@aol.com> wrote:
>>>after our tree-dwelling stage. I think it is obvious that the savanna
>>>would be a very dangerous place for our slow ancestors, and our
>ancestors
>>>could only have ventured out onto the savannas after they had developed
>>>suffecient tool technology in order to protect themselves.
>>>
>>>
>>>Troy Kelley
>
>>Well . . . I don't know . . . baboons seem to do okay.
>> Caroline R. Cooper
>> New to this Group & Truly Amazed
>
>Baboons are still quadrupedal and can run a fsf than any bipedal
>human, particulary one of Lucy's stature.
>
>Baboon males have truly awesome fangs; even leopards stay well
>clear.
>
>Baboons are still good climbers, so they retreat to the nearest trees
>when danger threatens.
>
>Baboons can go far longer without water than any human.
>
>Baboons are still hairy. They are not profuse eccrine sweaters
>like humans.
>
>If the savannah theory had any validity, then we'd be much more
>like baboons than we are. They are adapted to the savannah.
>Humans, without tools, aren't.
>
>Pat Dooley
Pat,
Humans and baboons have not shared a common ancestor for more
than 35 million years. It is therefore unlikely that hominids
moving onto a savannah environment would adapt to the savannah
like baboons.
Evolution is an interaction between geneology and the environment.
The result is that the current morphology of a species is constrained
by morphological changes and adaptations that have occurred in the
past. You might say that the past structures the present.
Cercopithecoid monkeys are very specialized when compared to apes.
There is a general notion that apes evolved from monkeys but this
is not the case. Both apes and monkeys share a generalized
anthropoid ancestor. Monkeys have gone off in one direction and
in the Miocene their lineage became very specialized. They developed
very specialized, bilophodont molars where apes retained very
generalized, primitive molars. The limb morphology in which the
hind limbs are longer than the forelimbs. The elbow joints are
characterized by very long olecranon processes on the ulna. All
of the above indicates a very specialized adaptation to arboreal
and terrestrial quadrupedalism. When cercopithecoid monkeys
moved out onto the savannah in the Miocene they did so with
the "scars of their evolution" which placed limits on the direction
they could take in terms of locomotor behaviors. Baboons, for
example, have a very specialized type of quadrupedalism in which
they walk on their fingertips (digitigrade).
Apes, be contrast, did not develop these specialized locomotor
adaptations. For all living apes, the forelimbs are longer than
the hindlimbs. Apes are primarily suspensory feeders, an adapation
that the lesser apes (gibbons) have really run with. Apes have
short olecranon processes on the ulna, have a more generalized
wrist morphology and on the whole tend to walk bipedally more
than monkeys. When terrestrial, orangutans "fist-walk" while
gorillas and chimpanzees "knuckle-walk." All of the present
evidence suggest that these are recent innovations and were not
present in the hominid-pongid common ancestor.
Therefore, when monkeys and proto-hominids moved onto the savannah
they did so with different sets of evolutionary baggage. You
mention sweat glands and this is another example. Monkeys have
few eccrine glands while apes in general have a 50/50 distribution.
Therefore monkeys moved onto the savannah without the advantage of
sweat as a heat rejection system. As a result, baboons do not
move about much during the hottest part of. If we assume
that protohominids had at least a 50/50 distribution then it
would seem they had the mechanism for sweating mostly in place.
AS above, they have different sets of baggage and therefore
adapt differently.
This is why I have stated repeatedly that the "Why don't baboons
do it ...?" kind of argument is bogus. Convergence may occur,
given enough time and strong enough selection pressures but if
you look at all the examples you have cited of convergence they
have all required much more than the 2 million years of time you
have open in the AAH. Evolution must work with materials at hand
and in general acts divergently, rather than convergently.
Now I have taken the time to provide a very detailed explanation
for one of my main pet peeves with AAH proponents. I suggest
you consult a more rigorous and comprehensive text on evolutionary
theory. I highly recommend Verne Grant's book (Evolutionary Theory)
or similar works by Douglas Futuyama or Ayers.
--
Philip "Chris" Nicholls Department of Anthropology
Institute for Hydrohominoid Studies SUNY Albany
University of Ediacara pn8886@cnsunix.albany.edu
"Semper Alouatta"
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