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From: jenkins@arthur.cs.purdue.edu (Colin Jenkins)
Newsgroups: sci.misc,sci.bio,soc.women
Subject: Re: Univerrsal Common Female Ancestor
Message-ID: <2052@arthur.cs.purdue.edu>
Date: Thu, 15-Oct-87 11:13:16 EDT
Article-I.D.: arthur.2052
Posted: Thu Oct 15 11:13:16 1987
Date-Received: Sat, 17-Oct-87 08:51:16 EDT
References: <2567@sigi.Colorado.EDU>
Organization: Department of Computer Science, Purdue University
Lines: 60
Xref: mnetor sci.misc:565 sci.bio:753 soc.women:7783

in article <2567@sigi.Colorado.EDU>, pell@boulder.Colorado.EDU (Anthony Pelletier) says:
> (Colin Jenkins) writes: (in response to me)
>>> I'm confused here.  Would anyone have suggested that humans evoloved more
>>> than once? 
> Colin:
> 
>>I recall from my genetics courses that many genes mutate in similar ways with
>>significant statistical frequencies.  Of course, this doesn't *prove* anything
>>about the existance of multiple or singular ancestors,but [it is possible]
>>
>>My impression of evolution is not that a single momentous event could have
>>occurred, but rather a series of such events.  If, after each significant
>>mutation, a large quantity of offspring was produced, then the next step in
>>the sequence would have a significant statistical likelihood in a large base
>>of individuals, not just one, and so on for each significant mutation.
> 
> Of course we are arguing in the dark here--proof would be hard to come by.

Sure, but it is interesting to kick around a bit...

	[ Describes good Bio book where authors believe each major 
	  event in evolution happened once				]

> Our mitochondria should be direct decendants of not only the first Human, but
> also the first euk.  It seem logical that, given speciation of a new mammal
> has not been observed as long as man has been keeping track, it is a rare event.

I'm not sure that logic supports you here.  I would guess that man has been
"keeping track" for not more than 2000 years (probably a lot less).  Evolution
is thought to require millions of years, so not seeing a new mamal recently
is not a good foundation to base a claim about evolution on.

> I imagine speciation in the following way (here I am way out of my line):
> Some event occurs (eg. a chromosome re-arrangement) such that an offspring can
> not mate productively, or, at least not have fertile offspring, with any
> members of the group except its parent or perhaps its siblings.
> Offsping of these matings are also constrained in there mating.  

On this point (and I am just as far out of my line at this point) I have 
trouble because such a breeding incompatibility would probably only come about
through radical genetic changes, rather than small ones.  I don't think that
evolution supports an idea of radical change, rather gradual changes selected
by the environmental factors to be passed on through reproduction.

The other problem with this thought is that it seems to presuppose that the
mutant will be somehow aware of its reproductive incompatabilities and make
the fortunate choice of breeding with its relatives.  More complicated is the
fact that the none of the other relatives may have received the mutations, so
they should have just as much difficulty mating with the mutant as any other
normal organism.

I saw a National Geograpic or Nova on the "Eve" issue and I thought that 
particular program went on to suggest that Cro Magnums may have interbred with 
Neanderthols, considered to be seperate species.  (Did anyone see it?  I was
in the kitchen suffering through meal preparation and could only hear the
television.  My memory is only sketchy on the show).

> -tony

				Colin