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RE: Microraptor also ate fish



I've enjoyed how this thread has progressed.  It's discussed quite a few ideas 
that would have strengthened Xing et al.'s paper.  On this latest point of 
contention between Tim and Jason, I think there's a broad, somewhat All 
Yesterdays issue involved.

Tim Williams wrote-

> (1) There is a difference between what an animal is adapted for, and
> what it is capable of. Obviously, the latter is more expansive than
> the former. (I can climb some trees - but I have no arboreal
> adaptations.) However, if an animal is not morphologically adapted
> for a certain behavior, then I think it is dangerous to argue that
> this behavior was central to its ecology.
>
> You say, quite reasonably: "Thus I defend any researcher who presents
> a hypothesis about extinct animals based on observations of living
> animals." However... unless that hypothesis is testable (e.g., by
> biomechanics, morphometrics, etc), then it is just speculation. (BTW,
> speculation is fine - as long as it's presented as such.)

As paleontologists, it seems to me we often assume a behavior was not normal 
without some obvious adaptation to it.  But is this a realistic view of how 
adaptation and behavior work in living animals?  I'm not talking about rare but 
possible behaviors like goats climbing trees, but about behaviors that living 
animals actually perform on a regular basis.  For instance, are there any 
studies demonstrating species that spend a certain amount of time in trees have 
a certain amount of arboreal adaptations?  Or is it possible/likely that say, 
20% of species that spend >30% of their time in trees can't be statistically 
separated based on skeletal morphology from 20% of species that spend <5% of 
their time in trees?  If the error bars and overlap are large enough, it would 
seem the right answer would just be to say "I don't know".  

This is especially true for taxa like Microraptor that fall outside the range 
of living taxa in their basic anatomy.  While we fixate on a few variables like 
pedal claw curvature, there are no doubt numero
pecies are adapted to arboreality, those will depend on the kind of animal 
being discussed, and features lacking in some species will be compensated for 
by other features.  Other features will only work in microenvironments that 
we'll probably never pin down for most extinct species.  

This all boils down to whether we're actually justified in using the tiny 
amount of information we have on extinct animal behavior to say anything 
significantly likely to be true.  Without some broader study on the kinds and 
frequencies of arboreal adaptations today, and the influence of novel variables 
such as Microraptor's clawed wings and solid mobile tail make, can we even make 
a useful statement about its arboreality?  Or is this more like when a 
phylogenetic analysis favors one relationship over another by only a few steps, 
where while one topology is technically more likely, it's actually more 
realistic to say the conclusion is uncertain.

Mickey Mortimer