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From: jnp@calmasd.GE.COM (John Pantone)
Newsgroups: sci.bio,sci.misc
Subject: Re: Unusual characteristics of Humans
Message-ID: <2633@calmasd.GE.COM>
Date: 22 Jan 88 19:18:26 GMT
References: <517@gtx.com> <5129@cit-vax.Caltech.Edu> <2201@bloom-beacon.MIT.EDU> <23465@cca.CCA.COM>
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Peter da Silva writes:
>There just aren't that many qualitative differences between humans and other
>species... most of the differences are in degree rather than kind.

Richard Harter responds:
> This isn't true.  It is true that humans are mammals and retain many of the
> body plan features of mammals.  However humans are quite unusual.  They have
> unique characteristics and others that are very rare.  Many differences are
> so marked that they constitute a difference of kind rather than merely 
> degree.  Here is a partial list.


Actually, I think they are both "right".  The chemistry, anatomy and even
behavior of humans is much more LIKE other mammals than UNLIKE, but there
are several notable differences

> (1)	Upright posture.  There are, and have been many bipeds.  However
> all other bipeds keep the spine at right angles to the body and balance
> the body over the legs.  Humans rotate the spine so that it is vertical
> over the legs.

I have usually heard this as rotating the pelvis not the spine - but it is
really the same thing - our cranium is unusual also, in that the spinal
attachment is more "antero-ventral" than in our close relatives the apes -
putting the head "on-top" of the spine rather than "in front" of it.

The fact remains, though, that from the navel down we are rather a great
deal different than the apes, from the navel up (even head/brain included)
we are quite a bit alike. It has been said, in defense of the concept of
Neoteny as a major force in the evolution of humans, that an adult human is
very close in form to a foetal chimp.

> (4)	Big brains.  Humans have much bigger brains (particularly
> cerebral cortex) for their body weight than any other animal.

	I have always questioned this - chimps gorillas and orangs, as well
as most of the cetaceans (sp?) all have complex cerebral cortexes (corti?).
Although the baleen whales can't compare in brain/body-weight to humans -
their brains are hugely larger than ours - and their body form is so
radically different from ours that a body weight comparison seems awfully
weak.  I think our brains are actually less "different" than we think.
(Except perhaps in function - but not in form).
 
> (5)	Complex non-instinctual social behaviour.   Again the difference
> is so large as to be a difference in kind rather one of quantity.

	I disagree - many animals have complex social behavior - monkees,
canines, etc.  I think that our actual behaviour is really a difference in
quantity not kind.

> (6)	A true opposable thumb.   I think that this is unique to humans
> among vertebrates.  The Panda does have an opposable "thumb" which is
> actually an enlarged wrist bone.
	
	What makes it "true"?  Chimps (especially the pygmy chimp) have a
very well opposable thumb.  Much, Much better than the Panda's (great, not
red).  Koala "bears" have 2 opposable thumbs (at least on their
forelegs/arms).  Check out your "opposable" thumb - it really doesn't truely
oppose any finger, except perhaps the little finger - it is "off center" of
all the others.

> (7)	An advanced tool user.  Other animals do use tools upon occasion.
> However they lack the structural modifications needed for tool using.
> Again, a difference in kind.

	This one puzzles me - what structural modifications? (opposable
thumb? - see above).
> 
> (8)	Cursorial hunter adaptations.  Not unique, but rare.  Cursorial
> hunters kill game by chasing it until it gives up.

	Not unique - true, also not rare.  Virtually all canines use this
means of hunting - in fact it has been suggested that the fundamental reason
for the human/canine association is the sharing of this (and pack) behavior.

	Wolves, wild dogs, cyotes - all Cursorial hunters, none - even today
- rare.


	All in all - I am still more likely to say that we are far more like
other animals than we are different.

-- 
These opinions are solely mine and in no way reflect those of my employer.  
John M. Pantone @ GE/Calma R&D, 9805 Scranton Rd., San Diego, CA 92121
...{ucbvax|decvax}!sdcsvax!calmasd!jnp   jnp@calmasd.GE.COM   GEnie: J.PANTONE