Xref: utzoo sci.bio:1023 soc.men:3116 talk.origins:1167
Path: utzoo!mnetor!uunet!husc6!cmcl2!nrl-cmf!ames!oliveb!3comvax!michaelm
From: michaelm@vax.3Com.Com (Michael McNeil)
Newsgroups: sci.bio,soc.men,talk.origins
Subject: Re: sexual selection and investment
Message-ID: <1137@3comvax.3Com.Com>
Date: 26 Mar 88 03:53:16 GMT
References: <1988Mar13.160941.22096@utzoo.uucp> <25527@cca.CCA.COM> <2403@saturn.ucsc.edu> <25669@cca.CCA.COM> <1125@3comvax.3Com.Com> <4736@aw.sei.cmu.edu>
Reply-To: michaelm@3comvax.UUCP (Michael McNeil)
Followup-To: sci.bio,talk.origins
Organization: 3Com Corp., Santa Clara, CA
Lines: 43

In article <4736@aw.sei.cmu.edu> firth@bd.sei.cmu.edu.UUCP (Robert Firth)
writes:
>In article <1125@3comvax.3Com.Com> michaelm@3comvax.UUCP (Michael McNeil)
>writes:
>
>>I might also add that since our closest living relatives are the
>>gorillas and chimpanzees, which are much more markedly dimorphic,
>>humans most probably lost much dimorphism during our evolution.  
>
>Well, since both pongos and chimpanzees are more highly differentiated
>than humans (and read that as "more evolved" if you wish), it is not
>impossible that the opposite is the case - that they have gained
>some dimorphism rather than that we have lost some.

I agree it's *not impossible* that chimpanzees and gorillas gained
dimorphism rather than humans having lost it, but it's less probable.
The reason is due to the fact that humans, chimpanzees, and gorillas
apparently are roughly equally divergent from a common ancestor.  In
such a three-way branching situation, if two species share a trait --
such as the knuckle-walking behavior of chimpanzees and gorillas -- it
is quite likely that our common ancestor possessed that trait as well.  
The alternative -- that convergent evolution independently invented a
trait within different species -- is of course possible, but generally
considered somewhat less likely, depending on the trait's complexity.

Follow-ups to sci.bio and talk.origins.

Michael McNeil
3Com Corporation
Santa Clara, California
	{hplabs|fortune|idi|ihnp4|tolerant|allegra|glacier|olhqma}
	!oliveb!3comvax!michaelm

	...  It is often said that all the conditions for the first
	production of a living organism are now present, which could
	ever have been present.  But if (and oh! what a big if!) we
	could conceive in some warm little pond, with all sorts of
	ammonia and phosphoric salts, light, heat, electricity, etc.,
	present, that a proteine compound was chemically formed ready
	to undergo still more complex changes, at the present day such
	matter would be instantly devoured or absorbed, which would
	not have been the case before living creatures were formed.  
		Charles Darwin, 1871