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Humans, 'droids, and convergent evolution



Well, is it all so really cut and dried?

I suppose that it isn't inenvitable that an intelligent dino would look
a lot like us.

But, I also know there is this thing called convergent evolution where
the same basic traits evolved independently several times.  I read
somewhere (Technology Review magazine maybe 6 mo ago) that biologists
think eyes independently evolved as many as 65 separate times.  They
differ a lot if you look close, apparently, but superficially, they
look a lot alike and do share many biological traits.

And, bipedalism and opposable thumbs seem (so far) to be distinctions that,
along with large brains, make _some creature_ likely to evolve into the
role we now hold.  Perhaps the nondino plesiousaurs could have been today's
cetaceans, but such intelligence (so far) doesn't seem to have much
significance.

In other words, if you look at primates generally, you will realize while
there was nothing foreordained about homo sapiens winning the "race"
to top thinker, it looks very much to me like, in the only extant case,
that the intelligent creature was going to have opposable thumbs and walk
on two feet on land.  Such traits do limit the potential body forms and
it would
be inevitable that pattern matchers like us would end up projecting a lot
of similarity on whatever emerged.  How much the limitations turn out to
be I can't possibly speculate well, but I imagine comparative biologists would
look first at the extant models, because the one argument I hear over and
over again from biologists is that forms are a certain way for a good reason.
In other words, looking a fair amount like us is probably a good
first approximation.

It strikes me that there are many bipedal dinos who could have evolved in
our general way -- maybe the big difference would have been in the tail (not
clear we couldn't have had tails), but I think in many key aspects, the
creature would have ended up looking a lot like us in size, proportions, and
general layout, because bipedalism and opposable thumbs, like everything
else in biology, aren't disconnected from everything else (and, their
relative importance would possibly magnify their effects on the rest of
the body.  The large brain, too, could limit things like the
pelvis; even an egg laying intelligence would have to lay a comparatively
large egg since one presumes the gestation outside of the mother's body
could not be excessive and so some of the brain case would have to
develop in a mammal-like way even if within an egg).

Ah, but what do I know?  Maybe those more professionally trained can tell
me where I go wrong.


Larry W. Loen (lwloen@rchland.vnet.ibm.com)
Department 52P
IBM   Rochester, Minnesota
         (507)253-3535
t/l      553-3535