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Re: Ceratopsian paraphernalia

Steve Jackson said:

>Whatever the horns and frill were for, whether it was defense,
>intraspecific combat or pure show, they were *good* at it. I say this
>because these characters developed and differentiated so quickly, while the
>rest of the ceratopsian body changed very slowly. In a large and presumably
>slow-breeding species, rapid evolution of a character would seem to imply
>that very strong selection was taking place. Ergo, even a small difference
>in a character made a big difference in its possessor's chance of breeding.

Usually, when a character is important to the species, it is highly
conserved.  Characters which are *not* particularly significant evolve
rapidly and more-or-less randomly.  An exception are those chraracters that,
possibly because of some external change, are no longer near optimum for the
environment.  These evolve directionally, and in the blink of an
evolutionary eye rather than over millions of years.  

The variability in the ceratopsian frill and horns indicates that frill
morphology and horn arrangement weren't that important to species survival.
Random genetic drift of these characters was not likely to be immediately
"corrected" by natural selection.


>valuable. I'd conclude that the primary driver of ceratopsian headgear
>evolution was sexual display, but when certain characters became useful for
>attack or defense, that began to drive their development as well.

Exactly.  The purposes of display or mate recognition characters are to let
potential mates (and rivals) know you're the right tribe or species and that
you have sufficient health and wealth to help support the mate and potential
offspring in the style to which they would like to become accustomed.  The
function is important, but the strategy is arbitrary.  The Rolex and the
Lexus both send the same message.  The fact that one tells time and the
other provides transportation are pretty insignificant, since both functions
can be performed more efficiently for a fraction of the price.  This is one
reason I doubt the horns had much significance for defense.

And before any of you start to feel superior about Rolices and Lexi,
remember I could as easily have said "the beard and the assistant
professorship."  It all depends on what species you're trying to attract ...

  --Toby White