Dragonflies and mosquitoes...


and the incomplete nature of evolutionary explanations.

If you take walks in the country in the summer, you have almost certainly observed that you will get bitten by mosquitoes much more often in the shade than in the sunlight. Why? Well, the evolutionary explanation that I've heard (and it seems perfectly sound as far as it goes), is that a major predator of the mosquito is the dragonfly, and dragonflies only fly in the sun, so mosquitoes have evolved to fly in the shade in order to stay away from them.

Excellent... But then why haven't dragonflies subsequently evolved to be able to fly in the shade, and go get the mosquitoes where they are?

Again, I'm not saying that last question shows that the explanation on offer is wrong: I think it is most likely correct, as far as it goes. I am just noting that it leaves much unexplained.

4 comments:

  1. It's common for a species to fall into a local optimum where there is no "upgrade path" consistent with the constraints of evolutionary adaptation (i.e. where each generation must be a local fitness improvement) -- that's one of the exact things evolution is ideal for explaining.

    It's common to see things like the recurrent laryngeal nerve or optic never where each generation saw a fitness improvement in structure, but over time they end up with some that makes you want to say, "geez, just cut that out and punch straight through".

    Evolutionary theory would suggest that dragonflies require a sort of complex adaptation that lacks the above kind of "upgrade path".

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    1. Yes, that is likely correct. I actually thought of putting a note in the post stating something like that.

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  2. "It's common for a species to fall into a local optimum where there is no "upgrade path" consistent with the constraints of evolutionary adaptation (i.e. where each generation must be a local fitness improvement) -- that's one of the exact things evolution is ideal for explaining."

    Actually Silas, evolution is (apparently) ideal for explaining ANYthing. Unbelievable complexity that seems to be designed? Evolution.

    Get stuck in a rut? Evolution.

    Complex structure that apparently exhibits irreducible complexity, such that any evolutionary story would get stuck at a local optimum? "Your lack of imagination is no strike against our theory" is what the PhD biologists say. (I mean, the ones who dismiss intelligent design and are thus *good* PhD biologists.)

    NOTE: The above is not intended to dismiss the scientific work on evolutionary theory. I am talking about the rhetoric.

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    1. "Unbelievable complexity that seems to be designed? Evolution."

      I have an affinity for guided evolution, but I can see no "unbelievable complexity that seems to be designed".

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