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Re: Little skulls...



At 03:55 PM 10/20/99 -0700, dbensen wrote:
>
>This points toward a complex series of instinctual behaviors. 

Partly, and partly natural selection.  The actual appearance of the eggs
tends to change after they change hosts.

> I can see why
>cuckoos would instinctually switch from one host species to another when the
>first began to reject foreign eggs, but why would the host species _lose_ that
>trait so quickly?

It is not *that* quickly.  The papers suggests tens or hundreds of
thousands of years, if not longer.  It is probably due to relaxed
selection, allowing accumulated mutations to decompose the defensive
behaviors.  Indeed there may even be selection *against* some of the
defensive behaviors, to the extent they reduce reproductive efficiency in
the *absence* of cuckoo eggs.

>  Is there _any_ benefit to having your offspring killed and
>then caring for a baby that isn't yours?

No, but in the absence of the cuckoos there may be costs to the defensive
behaviors, such as occasionally rejecting ones *own* eggs, or not having as
much food to feed the young.

--------------
May the peace of God be with you.         sarima@ix.netcom.com