Re: An end to miracles (was Re: New alvarezsaurid)

[Dinogeorge <Dinogeorge@aol.com>]

In a message dated 98-04-01 06:37:19 EST, jwoolf@erinet.com writes:

<< Stupid question, maybe: if BCF is correct, then why are the oldest known
theropods (_Eoraptor_, _Herrerasaurus_) among the least birdlike theropods?>>

Well, they're more birdlike than sauropods! Those dinosaurs are at the base of
the dinosaur cladogram; neither BADD nor BCF expects them to be as birdlike as
those dinosaurs closer to the avian groups.

<<Something here I don't understand.  There are a lot of arboreal animals that
do
 perfectly well without _any_ adaptations that could be even remotely
interpreted
 as leading toward flight.  So it's possible to be arboreal without being
directed
 onto a 'pre-flying' path by evolution.  Why, then, would these mini-dinos
have
 started that path?  What did it offer them that it does not offer, say,
squirrels?>>

Just because certain animals are arboreal is no reason to expect them >all< to
evolve into powered fliers (although they might, given enough time and the
extinction of all other powered fliers!). Just as, for example, the seas are
still filled with fish, even though a few evolved the ability to walk on land
about 400 Ma. We have no idea >why< dino-birds evolved powered flight--this is
probably unknowable, one of those strings of evolutionary contingencies that
occurred by natural selection and resulted in birds (and another string
resulted in pterosaurs, and another in bats). Likewise, for example, we have
no idea >why< humans evolved large brains (but lots of utterly untestable
speculation); we only know that they did.