Re: Savanna: a slow demise
Phil Nicholls (pnich@globalone.net)
Mon, 25 Sep 1995 04:35:12 GMT
Elaine Morgan <Elaine@desco.demon.co.uk> graced us with the following
words:
> Pnich says there is no such thing as savannah theory, only a
>range of ideas about what the habitat may have been, and the savannah
>naturally gets a frequent mention.
>That sounds fine. But in answering the question of why we are
>different from the apes, nearly everyone assumes that it was due to
>some change in the habitat.
Elaine, this is the part of your reasoning that really I find rather
odd. Why shouldn't we be different from apes? Why do you seem to
find the fact that we are different from the apes in a number of
respects so odd? More importantly, perhaps, why do you feel that the
differences between humans and apes should be attributed to a single
factor?
Nearly everyone does NOT assume that the differences between humans
and apes are due to some change in habitat. Try change in niche and
you will be closer to the mark. Some six to eight million years ago
an adaptive radiation of apes in Africa produced several new species.
Some became extinct, some gave rise to modern great apes and one gave
rise to hominids. That's why humans and apes are different. They
have been evolving separately for the last eight million years. Apes
have remained in the forest while hominids have diversified. One
group is specialized, the other extremely generalized.
>And until quite recently, whenever any of
>them got down to hypothesising what it was in the habitat that caused
>the speciation and the changes, nine out of ten attributed it to
>savanna-type conditions, whether they used the term or not.
>It was because conditions were arid, or plant food was scarce, or because
>they were chasing herbivores.
Now let's see, why is this? Could it be because early hominids are
obviously terrestrial and usually found associated with savannah
habitats?
> A very few, like Lovejoy, suggested
>that bipedalism predated leaving the forests. Now a few like Hunt
>are looking for new explanations, but this is quite recent. Wheeler
>talks about mosaic conditions, but when explaining bipedalism or hair
>loss, he still assumes the heat and the overhead sun and the
>hyperthermia were the operant factors, for lack of anything better to
>suggest.
And what did Wheeler do, Elaine. He didn't just propose a
relationship between bipedalism and heat rejection. He TESTED his
ideas. But this is not a "savannah" theory as much as it is a heat
rejection hypothesis, one strengthened by the fact that he has gone to
the trouble of testing the implications of the model.
Now I know you have cited works critical of some of Wheeler's
conclusions and I have read those critiques AND Wheeler's response to
them. The fact is that if Wheeler is wrong he is wrong, but AAH is
not a winner by default.
>Savannah theory is not the theory that there was a savannah. It is the
>use of it as sufficient explanation of human divergence from the
>primate norm. I agree that that argument is a bit less explicitly in
>evidnce nowadays, but as a presumed causal condition for change it does
>not seem to have been replaced by anything nearly as convincing as
>the pristine S.T. seemed to be in Dart's day.
Niche vs Habitate, Elaine. Dart's hypothesis was called the
Osteodentokeratic hypothesis was was less focused on the savanna then
it was on what hominids were DOING on the savanna. Wheeler, Lovejoy
and Hunt likewise are at least looking at ecological niches and not
just habitats.
Your window of oportunity for an aquatic phase is rapidly shrinking in
the face of new paleoanthropological finds. Given this fact, given
the fact that you can't make any predictions about the fossil record
because all of your data involves solft tissues and given the fact
that all of this data comes from comparing MODERN humans to MODERN
apes I would have to say that it the demise of the AAH you should be
concerned with.
Phil Nicholls pnich@globalone.net
"To ask a question you must first know most of the answer"
-Robert Sheckley
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