Re: intelligent design and rabbit poo

On 24 May, 02:51, r norman <r_s_norman@xxxxxxxxxxxx> wrote:
On Wed, 23 May 2007 18:49:48 -0600, Desertphile

<desertph...@xxxxxxxxxx> wrote:
From "Flock of Dodos"
http://www.youtube.com/watch?v=ba_932EhxoY

Rabbits, rabbit poop, and unintelligent design.

Coprophagy (the polite term for shit-eating) is a quite normal
phenomenon in many animals. We humans are the weird ones in thinking
there is something "wrong" in it. And I happen to think it is an
exceptionally clever trick of evolution -- intelligent adaptation, if
you will. The fact is that animals can't digest cellulose so many
animals have internal bacteria to do it for them. Ruminants like
cows have special fermentation chambers early enough in their
digestive system so they can cough up the bacteria processed stuff
(and the bacteria, themselves), chew it again (the cud) and then run
it through the digestive system to take advantage of the yummy result.
Most other mammals can't do that; they do the bacterial fermentation
in their caecum which is at the junction between the small and large
intestine. So the bacterial product is produced too far back for them
to be able to digest. That is why they run the stuff through twice.

I never knew this. With hindsight, it's obvious that rodents would
need some kind of work-around to live off grass like ruminants can. I
note that in the circulatory system, alternative topologies have
arisen at least twice (I'm referring to the gut and the liver being
connected in series, and to the pituitary and something else), so I'm
a bit surprised this digestive recycling hasn't been implemented using
plumbing.

I must admit I've no idea how to estimate the relative costs in terms
of time to evolve, between a behavioural solution and a plumbing
solution. I would have thought the behavioural one would be more
difficult, because however difficult tee-junctions and pipes may be to
introduce from scratch, the total complexity is still a lot lower than
the neural hard-wiring needed for the behavioural solution.

The first time they produce soft, moist material fresh from the caecum
and filled with nutrients. The second time they produce the hard dry
pellets that are more familiar as rabbit or rodent droppings. That is
really an exceptionally efficient and practical way of doing things,
an excellent example of really clever "design" and one I used to use
frequently in teaching.


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