From: colby@bu-bio.bu.edu (Chris Colby)
Newsgroups: talk.origins
Subject: Re: evolution of sex
Summary: stuff about sex and beer -- nice combo, IMHO
Keywords: beer, must have some, soon
Date: 7 Apr 92 00:12:50 GMT
Reply-To: colby@bu-bio.UUCP (Chris Colby)
Organization: Biology Dept., Bost

In article <jrjjzx=@lynx.unm.edu> rsquires@cyclops.eece.unm.edu (Roger Squires) writes:
>In article <83037@bu.edu> colby@bu-bio.UUCP (Chris Colby) writes:

>>	The question of how sexual organisms evolved from asexual
>>ones was recently raised. This is one the most puzzling questions
>>in evolutionary biology today.

>Well, I've just come across this in The Origin of Species, and I thought
>it was interesting; I'd appreciate comments (but not ones about about
>being lazy or arrogant, please.  Ones on beer are fine - I like
>Bohemia (but then this is the Southwest) and a certain Australian
>stout.)

	Bohemia is pretty good. Are you thinking of Sheaf Stout? That's
the only Australian stout I can think of. Australia has some good beers.
There is a wheat beer called Red Back (named after the Australian
version of the black widow spider, I'm told) that is excellent. Oops, I
thought this was alt.beer for a second. But, this has to be at least as 
relevent as the "Does evolution effect your belief in god/santa/easter
bunny/great pumpkin/elvis" thread that never seems to die the death it
so richly deserves. Who cares?

>Does his "physiological division of labour" have any relation to reality?

[much Darwin deleted]

	Darwin's scheme that Roger outlined above is almost certainly
wrong. Angiosperms (vascular, seeded, flowering plants) share a common 
ancestor with gymnosperms (vascular, seeded plants). This group shares a 
common ancestor with ferns (vascular plants). This group shares a common
ancestor with bryophytes (non-vascular plants). Plants share a common
ancestor with protists. Plants and protists share a common ancestor with
fungi and animals. All these (eukaryotes) share a common ancestor with
prokaryotes and archaebacteria (branch order is not well established for
this split as far as I know). All these branches (I'm actually not
sure about archaebacteria) can undergo sexual reproduction. 

	It is very unlikely that sex evolved independently in
angiosperms, gymnosperms, ferns, mosses, etc. It is much more
parsimonious to assume they inherited this way of life from their
common ancestor. I would guess (but I don't know for sure) that
all eukaryotes acquired sex via descent from their protist-like
ancestor. (A quick clarification; Protists are not obligate
sexual organisms; all can reproduce asexually and only some sexually. 
Many that are sexual are isogamous (gametes not differentiated into
male and female).)
	
	Plants evolved from ancient chlorophytes (protists that can
reproduce sexually and asexually) so common descent,  rather than
multiple parallel evolution, is more likely. So, figuring out (as
Darwin was trying) how an asexual flowering plant could evolve into
a sexual one is not needed. Figuring out how sex evolved in protists
(or earlier -- I don't know) would seem to be the question. His
"physiological differentiation of labour" may have some merit, but
he applied it to an inappropriate level of the heirarchy.

>Roger Squires
>rsquires@cyclops.eece.unm.edu

Chris Colby 	---	 email: colby@bu-bio.bu.edu	---
"'My boy,' he said, 'you are descended from a long line of determined,
resourceful, microscopic tadpoles--champions every one.'"
 	--Kurt Vonnegut from "Galapagos"

Newsgroups: talk.origins