The Advantages of Being Eaten By Rats
If you want proof positive that the doctrine of Creationism is a bunch of hooey, check out this story about a parasite called Toxoplasma gondii. Toxoplasma has a fairly complex lifecycle. It lives in the digestive system of cats, but lays eggs that get crapped out and then consumed by rats. Once inside the rat, the eggs hatch and form cysts and hang out until the rat is in turn consumed by another cat. And so on.
The problem with this strategy is that rats tend to avoid cats, because of the difficulty inherent in surviving an eaten-by-cat event; in particular, they avoid areas that reek of cat urine. That is, most sane, healthy rats do. But not the Toxoplasma-infected:
Oxford scientists discovered that the minds of the infected rats have been subtly altered. In a series of experiments, they demonstrated that healthy rats will prudently avoid areas that have been doused with cat urine. In fact, when scientists test anti-anxiety drugs on rats, they use a whiff of cat urine to induce neurochemical panic.
However, it turns out that Toxoplasma-ridden rats show no such reaction. In fact, some of the infected rats actually seek out the cat urine-marked areas again and again. The parasite alters the mind (and thus the behavior) of the rat for its own benefit.
Now I suppose this is just as valid a way of life as any other: setting up shop in a cat’s guts, sampling streams of partially-digested edibles from the smorgasbord of waste that passes by, funneling your progeny through an intermediate rat or two. We all want our children to see the world. It’s valid. But it’s also crazy.
Think about it: if I was designing creation, and I decided that I needed just one more parasite to round things out, and I said hmm, I think I’ll call it Toxoplasma and, ok, I think Toxoplasma should live in a cat’s intestines, and also, yeah, their eggs should get crapped out and eaten by rats and then grow into little mind control cysts that make the rats easier to catch and eat … you’d probably think I was either joking or insane.
But all of that stuff makes perfect sense if you look at it from an evolutionary standpoint: it smacks not of design but of expediency, of one little thing leading to another little thing, on and on down the maze until you finally get to the end. The crazy circuitous route you took to get there might not make much in the way of sense, but it works, and from the evolutionary perspective that’s the only real criterion. Biological market forces are all about the effectiveness of your design, not its elegance.
I don’t think anyone would call Toxoplasma’s crazy lifecycle elegant, or even rational: but it works, and apparently it works well, and in the end everyone’s happy. Except the rats, of course.
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