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Adaptationism for and against

oculus-Pantheon.jpgMy passing comment on San Marco has triggered a really interesting debate at Larry’s place.  

Larry thinks I think nothing can be selectively neutral, however. This is wrong. I think that things can be at the same time, selectively neutral (in that there is no real selective difference between an allele or trait and its competing alleles or traits), which have a high absolute fitness (because they are alleles or traits that contribute to the overall reproductive investment of the organisms that carry them).

I’m presently in Rome with the worst sore feet, and a slew of memories and photographs. The Pantheon was brilliant. I wish I’d seen it before the Catholics ruined it.

7 Comments

  1. But at least by using it they were interested in preserving it. It might not exist at all today, otherwise.

  2. I think that things can be at the same time, selectively neutral (in that there is no real selective difference between an allele or trait and its competing alleles or traits), which have a high absolute fitness (because they are alleles or traits that contribute to the overall reproductive investment of the organisms that carry them).

    That’s about as clear as mud. Can you explain what you mean using different words?

  3. John Wilkins John Wilkins

    Not while en route, but I’ll try anyway.

    Something is neutral if it has no real fitness difference to other alternatives in the population. Drift occurs when this is the case.

    But it is unlikely that any alternative in a population is completely inviable (given that completely inviable forms or genes will tend not to be expressed). So the population will have a high [absolute, not relative] fitness, since it is composed of viable organisms.

    Hence, selection can have acted on all genes/fitness in a population, and drift can occur on these high fitness genes/forms – once they are roughly of the same fitness.

    Drift opposes selection only when to drift the alternatives must be of low fitness.

    Incidentally, a gene or form that has gone to fixation has zero relative fitness, no matter why it went to fixation. Drift is an explanation of why that form or gene has fixed when there is no selective difference between alternatives in the population; not when there is no selection at all (for traits which make organisms survive to reproduce, for example).

  4. Something is neutral if it has no real fitness difference to other alternatives in the population. Drift occurs when this is the case.

    Actually random genetic drift occurs all the time. It’s why deleterious alleles are sometimes fixed and it’s why beneficial alleles are usually lost before they are fixed.

    I hope that’s what you meant.

    As for the rest of your response, I’ll have to read it several more times to make sure I don’t understand it. 🙂

  5. Divalent Divalent

    Actually, things are always drifting if there is more than one allele in play, even when one of them gives a fitness advantage. Neutral drift occurs on a level fitness plane, whereas if there is any fitness advantage or disadvantage, it occurs on a sloped plane (where to angle of the slope is a function of the fitness advantage). And sometimes a staggering drunk can end up going up hill, even though the odds are that he goes downhill.

  6. AntiquatedTory AntiquatedTory

    Nice picture of the Pantheon ceiling. It isn’t very convincing as a Christian place of worship, is it? (I guess that the Church Christianized it sometime before “Catholic” would have been a meaningful term. Well, Hagia Sophia is not the most convincing mosque, either.)
    Hope you didn’t eat there, the restaurants are horrid. Friend showed us a surprisingly edible pizzaria 3 blocks behind the Pantheon.
    How many Churches did you go into for their one Caravaggio [sp?] or other famous art work? And of those, how many had an annoying group of Italian secondary school students babbling into mobile phones?
    Yes, I recollect travels by restaurants. No, I do not have anything of scientific interest to say.

  7. AntiquatedTory AntiquatedTory

    I shouldn’t post at 3 am. When I said that the restaurants were horrid, I meant the ones right around the Pantheon. According to our Maltese archaeologist friend, who was studying in Rome for a year, the only edible place anywhere in the vicinity was the aforementioned pizzeria she took us to. It was quite edible and her other culinary advice was spot on, so I took her word for the awfulness of the other places (they looked crap, I must say).

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