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Re: The use of offensive weapons (was Re: ANKYLOSAUR CLUBS *)



Mickey Rowe writes;

>> Consider horns in pronghorn.
>
>There are at least three difficulties with Rob's argument.  First and
>foremost is the assumption that structures evolve for a purpose.  Most
>any modern biologist will tell you that the evidence indicates
>otherwise.

[buzzing sound]

Actually, the opposite is true.  Biologists have been able to show that every
part of an animal is there for some reason.  Granted, there is some
preadaptation function involved in the generating of the part in the first
place, but the refinement (and ultimately the keeping of the part) is because it
is serves some purpose.  Any part of the animal which isn't needed is
subsequently lost.

>Second is his implicit assumption that the use to which
>pronghorns currently put their weaponry is the same as that to which
>their protohorned ancestors put theirs.

This isn't as big a stretch as one might think.  Structures that form, and are
subsequently kept, do so because it gives the animal an adaptive advantage which
helps insure a mate.  Ultimately, competition in evolution comes down to whether
an animal gets it's genes into the next generation (literally a life or death
issue).  This is why there are a wide variety of display/threat/bluff features
found on all vertebrate groups.  This is also why any weapon will ultimately be
used to fend off members of the animals own species.  Anti-predator function is
simply an extra benefit.

>Finally, Rob, you've been making very
>strong statements about the use to which ankylosaurs put their tail
>clubs.  You can't exactly expect us to accept that your statement is
>true just because you've given us one example with no indication as to
>why that example should be generalizable to ankylosaurs (or any other
>animals, for that matter), can you?

The pronghorn was simply one example.  There are millions of examples (one for
each species) which back up my statements.  Every single time that one finds an
unusual part on an animal (especially if it could be used as a weapon), it is
ultimately designed to be used against it's own species.

This has also been shown for many dinosaur groups.  Horns in ceratopians,
hornlets on theropods, and the thickened skull on pachycephalosaurs are simply
some of the examples of features found on the animal which are primarily used
for intraspecies combat.

>To flip this around, Rob, how willing would you be to accept the
>statement that ankylosaurs probably used their tail clubs to beat off
>predators, if for justification all I said was "look at how catfish
>use the spines on their fins"?

Do catfish use the spines against their own species?  If so, it would be another
point for me.  These spines would certianly be useful in solving a territorial
dispute.

Rob

***
"Don't Panic."
        -HGTTG