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Re: Bird origins




Caleb Lewis wrote:

> ><< My question is: How does evolution seem to know what to evolve or
> make
> > one species evolve into next? >>
> >
> >By natural selection.
>
> nononono.   I mean, when a creaure needs to adapt to its environment,
> how does evolution seem to know what to evolve to fit that environment?
> Furthermore, what about the dino-to-bird thing? What sparked that?

Caleb,
George is right.  When a parent has offspring, each of those offspring
(with the possible exception of identical twins) is just a bit different
from each of the others.  When the environment is changing, some of those
offspring are just a bit different in a way that fits the changes in the
environment better than their brothers and sisters fit those changes.  So
the animals with the lucky changes in the appropriate direction are more
likely to grow up and have more offspring than their siblings do.  And some
of these new offspring are different from their siblings in the same sorts
of way, and their children fit the new conditions even better.  This
continues on for generation after generation, and the process is called
natural selection.  Sometimes it happens very quickly, and sometimes it
takes millions of years, but 'evolution' doesn't 'know' ahead of time what
to evolve.  It's just that random changes in each generation make some
animals fit the new conditions better and some fit worse, and the ones who
are unlucky and don't have the appropriate changes can't get as much food,
and more of their eggs don't hatch, and their young aren't as likely to
survive to adulthood.  So their contribution to the total population
diminishes and vanishes, and the animals with the lucky changes contribute
more and more to the new population until they make up all of it.

I'll leave the dino-to-bird thing to folks who know more about it than I
do.
Best wishes,
Jim