Re: naked bipeds
H. M. Hubey (hubey@pegasus.montclair.edu)
20 Oct 1995 17:46:17 -0400
Alex Duncan <aduncan@mail.utexas.edu> writes:
>In article <45sdmd$8k9@longwood.cs.ucf.edu> Tom Clarke,
>clarke@longwood.cs.ucf.edu writes:
>>The problem is to get from hairy quadrapedalism to naked bipelism.
>>The route for the change must be positively adaptive at every step.
>>Hairy bipedalism has heat rejection problems. Naked quadrapedalism
>>has heat input problems and cold night problems.
>>How could these two changes happen in a "coordinated" fashion to
>>result in the successful hominid package?
>You betray some misunderstandings about evolution when you say the route
>for the change must be "positively adaptive at every step".
Negative feedback means that the input is in the opposite
direction to the actual direction of the variable. Positive
feedback means that the input is in the same direction.
The only thing missing is if there's no input or if the actual
variable has no direction. If there's no change at all (i.e.
in the genes/chromosomes, IOW no mutations) then it wouldn't matter
what the input was. There's always input because that's the
environment. If there's always mutation then zero is practically
nonexistent. That leaves either positive or negative. If it's not
positive it must be negative. For a good approximation we could
consider every change as positive or negative (even if we cannot
tell which it is).
A more
>realisitic statement would be that the route for the change must not be
>maladaptive at any step (or at least not too maladaptive). There is
>every reason to think that a great deal of what happens in evolution is
>random, and happens when newly evolved features are not selected for or
>against.
This third category is produced because we cannot tell simply
by looking (or any other way, at least these days) if the
change was adaptive (positive) or maladaptive(negative). But
regardless of whether we know which it is, it is one of them
almost all the time.
This is like the philosophical problem of whether a sound
has been made by a falling tree is nobody heard it. Sure
there's a sound; nobody heard it, that's all.
>As far as naked bipedalism goes: you seem fixated on the idea that
>functional hairlessness and bipedalism must have evolved at the same
>time. This is not a fixation shared by paleoanthropologists.
Is there any evidence one way or the other, aside from the usual
analogy? IOW do they say there was hair because the skull
looked a lot like a chimp? Hasn't this kind of thinking bitten
the dust at least once before i.e. brain growth lead to bipedalism
or something like that because it required tool use etc etc....
>1) They were small enough that they didn't have severe heat retention
>problems.
AAS doesn't care. They could have been someplace where they could have
kept warm. Of course, it could be true that they were still
hairy.
--
Regards, Mark
http://www.smns.montclair.edu/~hubey
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