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Re: flights of fancy (or "I'm brave, but I'm chicken****")



In a message dated 95-12-06 18:39:24 EST, ornstn@inforamp.net (Ronald
Orenstein) writes:

>>When there is no evidence either way, you opt for the explanation that
makes
>>more sense. 
>
>Well, perhaps, providing you can show WHY it makes more sense.  Obviously
>there are a number of reasonably knowledgeable people out there who do NOT
>think it makes more sense.

I think I've shown why I think it makes more sense--over and over and over.
Others can accept my reasons or not. It really makes little difference to me
at this point.

>And, of course, there is always the alternative of admitting our ignorance,
>putting our various hypotheses aside until further data appears, and
>waiting...

We get nowhere by waiting--"all things come to him who waits"
notwithstanding.

> Pigs _could_ evolve wings
>>sprouting out of their backs, but the fact that no known mammal has yet
done
>>so gives us a clue that it probably won't happen with pigs, either.
>
>You are being facetious, of course, but neither of the alternatives we are
>considering is even close to being as unlikely as this.

Heh, heh. Really?

>>Why didn't any other group of bipedal dinosaurs evolve arm-tucking, if it
>was
>>so beneficial?
>
>For the same reason that only one group of hoofed mammals evolved incredibly
>long necks, only one evolved large, highly-functional elongate trunks etc
>though both of these are clearly highly functional adaptations - because (a)
>they just didn't or (b) there were functional advantages for maniraptors to
>do so that did not exist for other dinos.  This is like saying that the
>retractile claws of cats could not have evolved as hunting adaptations
>because dogs don't have them.

Arm-tucking does not involve a particularly complex suite of characters. It
is on the order of the loss of the outer digits and the elongation of the
metapodials among cursorial animals. It could easily happen many times over,
if it were that advantageous. And here again, I'm not saying "could not have
evolved," I'm saying "unlikely to have evolved."

>>In _Goldfinger_ (Ian Fleming), the villain's motto is something like, "Once
>>is happenstance, twice is coincidence, and three times is enemy action."
 So
>>if I see three or more different flight-specific adaptations present in a
>>group of volant vertebrates, I assume they didn't just happen there by
>>coincidence.
>
>This is circular reasoning.  WHY are they flight-specific adaptations?
>"Because birds have them" isn't enough.

It's a damn good start. Big wings, trenchant claws, perching feet, flight
feathers, lightweight pneumatic skeleton, large eyes--what's the big picture
here? Ad hoc accumulation of random features, or a steady stream of features
gradually acquired as improvements to an acronomic lifestyle?

>>>Except that it might well have developed adaptations to counter this
>>>problem.  After all, an Ostrich is an extremely fast runner with
>>>fairly-large, well-feathered wings and it seems to manage.
>>
>>Yeah--or it could simply lose the feathers, which according to BCF happened
>>in most of the large-theropod lineages.
>>
>
>But for which you have, again, produced no evidence.  "It could have been"
>that way - or not.

Skin impressions of large theropods exist, and they show no feathers. On the
other hand, skin impressions of _Pelecanimimus_ do show some kind of
featherlike structures(!), albeit neither contour feathers nor flight
feathers.