Re: natural vs. sexual selection

[Stan Friesen <swf@ElSegundoCA.NCR.COM>]

 From: "c. brochu" <gator@mail.utexas.edu>
 > 
 > This may sound counterintuitive, but this is based on experimental and
 > observational evidence.  Had antelope - and, I think, ceratopsian - horns
 > evolved primarily for defense, there should be much less interspecific
 > variation.

This is really considered pretty well established now.  The
discovery of apparent sexual dimosphism in the horns of ceratopsians
pretty much clinches the case for intraspecific display and combat
as the *primary* purpose.  (As if the bizarre frill horns of
Styracosaurus didn't do so already).

Similarly, the crests on hadrosaurs ("duckbills") are also *clearly*
a result of sexual selection - even more so than the ceratopsian
structures.


Again, when defending itself an animal is going to use *every*
means available to do so.  In Triceratops this means horns, hooves,
and beak (and a mean beak it is too).  This doesn't change the
*primary* purpose - hooves evolved for walking, the beak for
feeding, and the horns for mate selection.

swf@elsegundoca.ncr.com         sarima@netcom.com

The peace of God be with you.