Re: What is a Dinosaur? and semilunate carpal

["Tim Williams" <twilliams_alpha@hotmail.com>]

Dinogeorge wrote:

> Why fly
> at all? It helps to solve the Falling Problem for arboreal animals. It
> doesn't solve >any< problem for cursorial, ground-dwelling predators;
> ground-dwellers have no need to fly,

Well, they might want to catch flying insects in mid-air.  For example.

> Consequently ground-dwelling animals are extremely unlikely to be directly
> ancestral to flying animals outside the arboreal paradigm.

This comes down to a distinction between "plausible" and "possible".  If 
flight is _possible_ from the ground-up, then it becomes a _plausible_ 
explanation if the available evidence supports the closest relatives of 
birds and basal birds being ground-dwelling predators.  Evolution works on 
the raw materials available, and is not deterred because certain 
alternatives are biophysically "simpler" or "easier".

> If the evolution
> of flight from ground-dwelling animals is so plausible, why don't pigs and
> kangaroos and people have wings?

By the way, it is not as though we have a huge sample size to work with in 
determining which ecologies are more condusive to the evolution of flight.  
Wings evolved only THREE times in vertebrate evolution: pterosaurs, birds 
and bats.  And can you confidently claim that pterosaurs and bats also 
evolved from arboreal ancestors?

(Personally, I think all three groups of flying vertebrates evolved in the 
trees.  But the archives are crammed with my ramblings on this issue, so 
I'll hold off on further rambling here.)


> That's the kind of tautology that fails to drive the standard theory. 
> "Well,
> stiff hands must have been useful to them, otherwise they wouldn't have
> evolved them." Useful how? They were certainly useful when it came around 
> to
> acquiring wings, but what about when wings were still way off in the future
> of possibilities?

If BCF is to be credible at all, you're going to have to demonstrate that 
the maniraptoran hand was so "stiff" that it was ineffective (or even 
less-than-optimal) for grasping prey.

> A vertebrate wing isn't going to evolve by random
> chance; it's too complicated a structure. It's not going to evolve as a set
> of randomly acquired, undirected characters that just happen to assemble
> themselves into a wing, any more than a shattered cup will reassemble 
> itself
> when you throw the pieces back onto the table.

Exaptation, exaptation, exaptation....


Tim









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