[vhawk01]

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Daniel C. Dennett likes to tell the story about an ant crawling to the top of a blade of grass. It turn out that the ant's brain can be invaded by a parasitic worm, which need to get into the belly of a cow for survival. Thus (as Dennett puts it), it drives the ant like an all terrain vehicle up the blade of grass so a cow can digest it.

Well, I certainly have a healthy respect for evolution, but just how on earth did this worm evolve to know not only to invade the brain of the ant, but to then have an exact effect on the brain that causes it to climb up the blade of grass?

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(Insert usual "I wouldnt really have a clue but..." disclaimer here)

It would seem more plausible to me that it first evolved to live in an ant's brain. An unexpected side effect was that sometimes the ant got driven up the blade of grass, because of where the worm was nestled. Consequently a lot of them got eaten by cows. A few worm larvae or whatever happened to survive. Repeat many times. Gradually, the "living in a cow for a while" bit becomes essential (which would then provide an evolutionary advantage to those ants which happened to live near the "climb a blade of grass" part of the ants' brain)....

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You are very good at reverse engineering! I didn't think of that. Dennett simply states that the worm "needs" to get into the belly of a cow. So I assumed this preceded all, and that evolution somehow figured out the best way for for the worm to achieve this. But yes, if the cow came afterward, it makes much more sense.

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Its a common problem in discussing topics in evolution, this anthropomorphizing of the process, attributing intent, things like that. The reason is, it makes it easier to describe something by saying stuff like "Ok, so the worm needs to get here, so evolution creates this mechanism." It ends up being misleading and is obviously entirely incorrect, but it makes it more approachable. Dennett is probably the worst culprit of this, although I think Gould does it often and Dawkins also, to a lesser degree. Certainly, it is something that is RAMPANT in science textbooks and popular scientific writing. I always cringe a little bit when I read anyone talking about the goals or tactics or strategies that evolution uses to do things, but I also cringe when I read a general chemistry textbook and they talk about electrons in orbits and such. Its a balance, the writer tries his best, and you must consider the audience. Lestat, by posting here on SMP and reading the evolution debate in a very special context, you have a different perspective than the vast majority of readers. You know enough to cringe when you hear agency bestowed upon mindless processes (mindless added for NRs benefit) but perhaps don't have the experience or the repetition needed to translate those pop-speak phrases into what they really mean.