Racial Inbreeding

Discussion in 'Biology & Genetics' started by Willy, Aug 29, 2007.

  1. sniffy Banned Banned

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    A member of the human race 'breeds' with another member of the human race. A baby is born. Is this news where you lot come from?
     
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  3. fo3 acdcrocks Registered Senior Member

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    An allele that has a negative effect to fitness has better chances to survive if it is recessive, but in case of an allele increasing fitness relatively more than other alleles of the same gene, it would benefit the species a lot more if it was dominant instead of recessive and being expressed in the phenotype more often. That would indicate that there is a selectional pressure for "better" alleles to mutate into a dominant form while retaining its positive effect, instead of staying recessive indefinitely.
     
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  5. iceaura Valued Senior Member

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    Evolution does not proceed toward benefit, but away from culling.

    If there are two alleles, one of which is comparatively and definitely an inferior reproducer, the replacement of the inferior by the superior will happen much faster and more completely if the inferior is dominant compared with the superior.

    If the species "benefits" by that, so much the better - that would be a side effect.

    Once the inferior is culled, the remaining allele would have the gene pool to itself, with no need of "dominance".
     
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  7. Xylene Valued Senior Member

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    I heard that one of the reasons that the European race isn't generally dark-skinned is that when you go north of the 40th parallel, (or south for that matter) the sunlight doesn't provide enough Vitamin D if your skin is too dark. Lack of Vitamin D = rickets, which removes people from the gene pool because A) the can't hunt; B) they can't very easily even move around; C) they're extremely unlikely to be chosen as sexual partners for reasons A and B. Therefore, over the thousands of years of gradual movement into Europe by various groups--and also taking into account the atrociously damp, cold, foggy conditions that would have existed in ice-age Europe--the tendency for the dark-skinned people to have been left behind, literally and figuratively, in the sexual selection process would have been very strong.
     
  8. fo3 acdcrocks Registered Senior Member

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    The benefit for the species wouldn't be a side effect at all, it would be a reproductive advantage over other species competing for the same resources that do not tend to get as much dominant useful alleles as fast. This should be pretty much the idea of group selection, if I am correct.
     
  9. iceaura Valued Senior Member

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    But it would be a reproductive disadvantage for the superior allele - selection would not be eliminating its competition as fast or as completely.

    And it probably would be a disadvantage for the species as a whole, long term, carrying the burden of the inferior allele as an all but ineradicable recessive.

    That is indeed a common type and line of reasoning in "group selsction" - one of the reasons "group selection" is viewed with suspicion among evolutionary theorists.
     
  10. fo3 acdcrocks Registered Senior Member

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    I guess we can conclude that there are different levels of selection to be considered, and their interaction and level of importance in any given situation is difficult to evaluate. I did not think that my view would be the correct one in this situation, but I would still argue that having a beneficial allele in dominant position would have its advantages for a species, rather than having it in a recessive position and waiting for the less useful dominant allele to be eradicated. That should be especially important in situations where there is a fierce competition between species sharing the same ecological niche, and the long term benefit might mean a short time extinction, whereas a long term disadvantage might mean a short time success, allowing the species to handle the long term effects in a less competitive environment.
     

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