"Andrew Ward"  wrote in message
> Thanks for your reply,
> I still have trouble grasping this one though, I do understand what you
> are saying, however I find it hard to grasp how such a complex
> behaviour can manifest itself when it most likely requires as you say
> "many many genes and over-lapping functions...". For example, if
> some of the genes required for this behaviour became available but
> others were still lacking, would the existing genes not simply be
> selected out of the species over time before the fully required set
> become available?
> What I am trying to say is that anything less that the fully developed
> behaviour of watering the eggs would be of no use to the species,
> therefore how does the developing behaviour stay in the species long
> enough to fully develop?
>
This is partly the "what use is half a wing" question, which many
books deal
with.
A complex behaviour or structure cannot evolve at one stroke, there needs to
be a change of small stages, each of which offer some advantage.
In the case of the bird that cools egs with water, I don't know anything
about the species or its relatives, but I can suggest a "just so story".
Birds are selected to drink more water in hot temperatures. They also carry
water in their beaks to regurgitate to the young. Initially the first-born
chick is in the nest with unhatched eggs, and the unhatched eggs benefit by
water being accidentally dribbled over them. That behaviour is then modified
to dribbling lots of water over the eggs.

The other problem is, what is the physical basis of the behaviour? It is
unlikely that a bird has any insight into why it is watering eggs, but we
cannot absolutely rule it out. Our best theory is that behaviour is somehow
encoded in the neural connections in the bird's brain, which are partly
under genetic control. However there are too few genes to specify every
connection. So we are waiting for some fundamental breakthrough. The idea of
a "life-force" or "soul" animating behaviour, doesn't
seem likely, since
there is nothing like it in the rest of science (though humans may be a
special case). Since we don't really know, however, you are welcome to put
forwards a vitalist explanation if you can think of some way of testing it.
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