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Thread: Quick question about evolution

  1. #1 Quick question about evolution 
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    Hey, I made a similar thread recently, even though I just began on Darwin's "On the origin of species", I haven't quite a large understanding of evolution yet, and thus I have a question that's been bugging me pretty much. I understand that african people have black skin and asians have slanted eyes because of evolution. But how exactly so?

    First of all, if I've understood this correctly, both of those traits are because of random genetic mutations. Having slanted eyes in a snowy and cold envinronment might be useful, but it's not exactly necessary to survival. So how come ALL asian people have them, and not just some? And why do ALL black people have black skin all over their body? I mean, if someone in Portugal had a gene mutation so that their eyes were slanted, it wouldn't really make a difference, so I don't see why they haven't got it? Surely they must have had the same mutation along the way at least once in history?

    Also, one more question. My mom has this sort of excess cartilage inside her nose, lol, bear with me. I seem to have inherited that. Is that just the cause of a gene mutation too? In this case it wasn't helpful nor bad, just neutral, obviously. And was it just a sheer coincidence that I've got it too since my father has a "normal" nose? And if mutations are so normal, then why do we look so similar?


    Thanks for answering my noob q's


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    Over time, preferred genetic traits will breed into a group, essentially taking over as the norm. Not all Asians do have the Mongolian fold, but these days, those without are in the minority, by far.

    We carry a great deal of "neutral" DNA.


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    Quote Originally Posted by Neverfly View Post
    Over time, preferred genetic traits will breed into a group, essentially taking over as the norm. Not all Asians do have the Mongolian fold, but these days, those without are in the minority, by far.

    We carry a great deal of "neutral" DNA.
    But how did evolution know that the slanted eye trait was good? I don't quite understand it.
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    Evolution doesn't "know" anything.
    Slanted must have conferred some advantage and non-slanted eyes died out (or maybe it didn't confer a disadvantage - it was neutral - but there happened to be a preponderance of "slanted-eyed" people and it bred true).

    Wiki says that sexual selection may have played a part - if most people found "slant eyes" appealing then they'd obviously flourish.
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    Quote Originally Posted by Dywyddyr View Post
    Evolution doesn't "know" anything.
    Slanted must have conferred some advantage and non-slanted eyes died out (or maybe it didn't confer a disadvantage - it was neutral - but there happened to be a preponderance of "slanted-eyed" people and it bred true).
    Just as an aside "slanted" is not a great term in this context (and may be considered offensive by some people).

    The epicanthic fold is not unique to Asia. It occurs in some African populations and among Europeans. So it is obviously quite a common trait. It may be that it provided some advantage to nomadic peoples in the Central Asian steppes (keeping the dust out of their eyes, maybe). If this reduced, slightly, the risk of eye disease then it could be a survival advantage and spread through the population.

    Wiki says that sexual selection may have played a part - if most people found "slant eyes" appealing then they'd obviously flourish.
    That was the first thing that occurred to me.

    Although of course, it could be the other way round. Early hominids may have had the fold but it was lost in some populations due to, for example, sexual selection.

    (I have always thought "sexual selection" is a slightly misleading term...)
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    Quote Originally Posted by Strange View Post
    Just as an aside "slanted" is not a great term in this context (and may be considered offensive by some people).
    Yeah, my engineering lack-of-sensibilities/ disdain for PC got over-ridden partway through so I put "slanted" in inverted commas in an attempt to mitigate any possible offence.

    Apologies to anyone who took the use of the word as anything other than simple failure to type out "epicanthic fold".
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    Quote Originally Posted by Dywyddyr View Post
    Yeah, my engineering lack-of-sensibilities/ disdain for PC got over-ridden partway through so I put "slanted" in inverted commas in an attempt to mitigate any possible offence.
    In my case, the engineer in me goes, "but it's not even accurate!!1!"
    Without wishing to overstate my case, everything in the observable universe definitely has its origins in Northamptonshire -- Alan Moore
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    Perhaps the epicanthic fold didn't confer any advantage and simply carried over with some other trait that did. I'm reading "The Greatest Show On Earth" right now, and there is a discussion in there on how some traits will sort of come along for the ride as a secondary trait, not conferring any particular advantage, but piggybacking on the genes that conferred some other trait which did confer an advantage.

    Has anyone actually studied that particular topic? (genetics/evolution of the epicanthic fold)
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    On darker skin.
    This is a relatively easy change, since there are about 20 genes for skin pigmentation, and they vary a lot from individual to individual. If the population is living in an area with a strong ultra violet incidence, causing burning in light skinned individuals, then having a darker skin is an advantage.

    In fact, dark skinned traits have evolves many times. Also a wide range of intermediate skin types. South India, for example, has very dark skinned people, as does Sri Lanka. They have in common with equatorial Africa a very strong ultra violet flux. For that matter, my Pacific Island neighbors did the same for the same reason.
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