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Discussion and Debate
Discussion and Debate
Physical & Life Sciences
Creation & Evolution
Are we evolving?
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<blockquote data-quote="sfs" data-source="post: 44606352" data-attributes="member: 8727"><p>As far as evolutionary biology is concerned, this is the correct answer.(*) In a finite population evolution will occur, even if there are no selective pressures causing it to occur in any particular direction. In fact, since the main effect of natural selection is to <em>prevent</em> evolution, by weeding out deleterious mutations, removing selective pressure will generally increase evolution rather than slow it down. </p><p></p><p>At present humans have relatively low (but hardly zero) selective pressures operating on us. We also have a very large population size. That means there is little directional evolution happening, little overall change in frequencies for common variants (i.e. our population is large enough that it is starting to look a little like an infinite size), lots of accumulation of new, rare mutations, and more accumulation of mildly deleterious alleles than at most points in our history.</p><p></p><p>Animals in the zoo are a somewhat different story. They may be experiencing a tight genetic bottleneck, if the zoo population is genetically isolated from the outside population, or if the outside population is threatened with extinction. If that is true, they are evolving rapidly, with all allele frequencies changing. They are under less selection pressure for some traits that are important in the wild (e.g. speed, stealth), so those abilities are likely to slowly decay, while they may be under new selective pressure for other traits (e.g. docility, willingness to mate in captivity).</p><p></p><p>(*)I'm not really certain about the need for #2, at least in the context of an infinite population. Assortative mating will cause genotype frequencies to depart from those expected under Hardy-Weinberg equilibrium, but it's not obvious to me that it will cause allele frequencies to change in the population. I have the flu at the moment, however, and I'm trying to avoid thinking too hard about infinities.</p></blockquote><p></p>
[QUOTE="sfs, post: 44606352, member: 8727"] As far as evolutionary biology is concerned, this is the correct answer.(*) In a finite population evolution will occur, even if there are no selective pressures causing it to occur in any particular direction. In fact, since the main effect of natural selection is to [i]prevent[/i] evolution, by weeding out deleterious mutations, removing selective pressure will generally increase evolution rather than slow it down. At present humans have relatively low (but hardly zero) selective pressures operating on us. We also have a very large population size. That means there is little directional evolution happening, little overall change in frequencies for common variants (i.e. our population is large enough that it is starting to look a little like an infinite size), lots of accumulation of new, rare mutations, and more accumulation of mildly deleterious alleles than at most points in our history. Animals in the zoo are a somewhat different story. They may be experiencing a tight genetic bottleneck, if the zoo population is genetically isolated from the outside population, or if the outside population is threatened with extinction. If that is true, they are evolving rapidly, with all allele frequencies changing. They are under less selection pressure for some traits that are important in the wild (e.g. speed, stealth), so those abilities are likely to slowly decay, while they may be under new selective pressure for other traits (e.g. docility, willingness to mate in captivity). (*)I'm not really certain about the need for #2, at least in the context of an infinite population. Assortative mating will cause genotype frequencies to depart from those expected under Hardy-Weinberg equilibrium, but it's not obvious to me that it will cause allele frequencies to change in the population. I have the flu at the moment, however, and I'm trying to avoid thinking too hard about infinities. [/QUOTE]
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