Re: Amargasaurus...

["T. Mike Keesey" <tmk@dinosauricon.com>]

On Fri, 27 Apr 2001, Erik  Omtvedt wrote:

> >  Evolution doesn't always happen in the best way possible.
> >  Animals don't plan out their evolutionary strategies.Variations >  occur 
> > randomly, and natural selection weeds out the unfit
> >  variations.
>
> Yes and no. It isn't practical to look at life's creativity as any
> kind of mistake, to "try better next time around". Yes, unfit
> variations are weeded out through time, but chances are an animal as
> successful as a large sauropod (among the most successful of any
> animal group ever to roam the planet) would hardly develop such a
> fantastic "mutation"...as it sounds like you are saying...without some
> sort of adaptive need.  Granted, there is trial and error, but look at
> the scale and magnitude we are talking about. Not just the overall
> size, mind you, but the dimension of the feature in proportion to the
> animal. Is there any animal alive today which caries around such an
> obvious "burden" as this, I wonder?

There are animals with far worse burdens (porcupine sex?).

I hope it didn't sound as though I was proposing that the structures of
_Amargasaurus_ arose in one single mutation! I'm sure it was the result of
a gradual evolution, wherein individuals with slightly longer neck spines
somehow fared better than those without. Protection from predators could
certainly be a major factor. So could sexual display. Perhaps both.
Perhaps more.

I was mainly arguing against the "Why not just evolve armor?" argument.
The animals have no "choice" in this matter -- they make do with the
variations that do occur, or they die out. (Otherwise, I'd have "evolved"
a gigantic brain, falcon-keen vision, the ability to photosynthesize, and
internally-housed gonads by now :)

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T. MICHAEL KEESEY
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