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Re: A question concerning the BCF hypothesis



Hi!

I started some discussion on the BCF hypothesis. I'd like to continue it.

David Marjanovic wrote:

> << I'd say a four-chambered heart looks like a prerequisite for
endothermy,
>  doesn't it? >>

Dinogeorge wrote:

> This isn't obvious. Some fish are partially endothermic and they have
> two-chambered hearts.

Dinogeorge, do you mean the tuna fish? Or are there some others?

Dinogeorge also wrote:

"Evolution of a four-chambered heart would represent an >improvement< to
an arboreal animal but is certainly not a >prerequisite< for arboreality. It
would also represent an improvement to a terrestrial animal, however.
Separation of pulmonary circulation from systemic circulation seems to have
been a good thing all around. Probably more important to the evolution of
dinosaurs and birds than endothermy, for example."

So does the BCF hypothesis make statements about the original reason for the
four-chambered heart to evolve?

And, why would a four-chambered heart be an improvemet for an animal
climbing in the trees? No arboreal reptile I know has a four-chambered
heart. Of course it is possible that they've gotten stuck on some stupid
local adaptive peak and can't take the neccessary step backwards in order to
evolve a more complex heart, but I still think that the lack of arboreal
reptiles with four-chambered hearts tells us something.