Sunday, May 29, 2005

Cloaca: The Prediction

So most of the glass-cutting for the copper goldfish last night took place with Galaxy Quest in the background, but before that, Animal Planet had a sweet little program about beavers, their lives and families, and their interactions with humans.

They kept referring to the beaver's "cloaca" (and every time they pluralized it as "cloacas", I heard my classics prof uncle do a little pirouette in his grave!). Apparently, from a functional (physiological) point of view, the beaver's cloaca is a kind of sac, where secretions from scent glands are stored for marking territory later. For the moment, though, you should take this with a grain of salt until I verify it; I was much more focused on cutting the glass rather than myself, than on the program, but I think that's the gist of it. I don't remember their saying anything about it from a purely structural (anatomical) point of view.

An essential feature of the scientific method is that it allows you to make testable hypotheses. By contrast, a non-scientific paradigm, such as Intelligent Design or any of the other kinds of creationism, does not lend itself to testable hypotheses: if a supernatural event is responsible for the development of different species, there are no natural constraints on what it is able to do. Therefore, no species would necessarily be more like any other species, and there would be no reason to expect their genomes to exhibit any more similarity than you would find at random.

So here is my prediction: despite the name "cloaca", I predict that the embryology of the beaver's urogenital system is very different from the avian and reptilian cloacae, and very similar to the embryology of the urogenital system of other mammals, and that the beaver's cloaca has nothing to do with the structure of the same name in birds and reptiles. I base this hypothesis on the evolutionary history of the beaver as a fairly specialized mammal, relatively fairly distant phylogenetically from either reptiles or birds. I am going into this exploration cold, with no specific knowledge of beaver biology, and will report my results as I am able to gather them.


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