face evolution

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face evolution

Postby zetreque on October 28th, 2018, 1:35 pm 

Why has human facial features evolved differently in different parts of the world?
One example I read about a long time ago is the neanderthal nose being more adapt for the cooler air in northern Europe. What else?
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Re: face evolution

Postby Forest_Dump on October 28th, 2018, 2:31 pm 

Although some do try to explain everything in terms of adaptation to some external (i.e., environmental) factor, I for one, think many attributes may have been more a product of more stochastic (i.e., chance) factors. So, that some groups may have slightly different cheekbones or eye or hair colour may simply have been due to the fact that when one group went their seperate way they just happened to have a higher proportion of one variant in that gene pool (i.e., the founder effect) and chance fixed it a bit more. I know there have been attempts to explain some of these trends in terms of things like sexual selection but I don't find them to be overly convincing. Our species sees to always had a low population with relatively few offspring but with a lot of parental investment (k-selected) so, since there hasn't been a ton of time and generations, I am cautious about how much can be attributed to the kinds of things you might see if there was a lot of intensive selection over a very long period of time.
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Re: face evolution

Postby zetreque on October 28th, 2018, 2:58 pm 

Skin color seems to be the most obvious environmental adaptation. Eye color seems closely related to the same sunlight factor.

Some other thoughts are facial traits that may be similar to wild animals of the region.
The distance that was important for that group of people to see and spend the majority of time working with. Just saw a paper that said Asians are more likely to be nearsighted. Though the paper wasn't that convincing.
Humidity and temperature.
wind.
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Re: face evolution

Postby Serpent on October 28th, 2018, 3:03 pm 

The general form of human physiognomy is pretty much of kind - quite distinct from the other apes in length of snout, shape of mouth, placement of eye-sockets, proportion of upper and lower jaws, etc. There are only minor (though recognizable) variations in bone and cartilage structure; the soft tissue variants like lip shape and eyelid folds are superficial. The functionality differs very little, if at all.
Except for pigmentation, I suspect these variations were not a response to environmental conditions, but incidental. A small group of early people migrated to a region where there were no other people; they passed down the genes of their hardiest, best-adapted or most aggressive males. Over time, a limited gene pool will reinforce the dominant characteristics of the most prolific breeders. Over time, that superficial appearance would become the standard of beauty, and thus desirable in mates, even when no longer associated with substantial advantages.

This is only a guess, based on the family resemblance of people from the same part of England or Poland - a similarity of appearance that has nothing to do with advantage. Also dog-breeding.
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Re: face evolution

Postby Braininvat on October 28th, 2018, 5:03 pm 

Agree with Forest on the role of founder effect. Less impressed by theories I would hear growing up, such as the English tending to long thin noses because their culture equated that with an aristocratic quality. You hear a lot of theories about culture mediation of attraction that just don't hold up. An actress who I am smitten by, consider her smoking hot, has facial asymmetry and a somewhat snub nose, and I would court her (if I weren't, erm, married to the most beautiful and intelligent and sexy woman on the planet) (is she still looking over my shoulder?) before any of these austere modeling agency beauties so prevalent in mass media.

I've read research papers that point towards basic indicators of female fertility and adequate nutrition - full lips, good skin, rosy cheeks, strong shapely legs, etc. - are more determining male attraction (plus a nice smile) than any particular facial configuration.

Extreme climatic conditions, however, could favor some modifications. E. g. intense cold favoring a rounded face and smaller flatter nose to reduce frostbite chances.
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Re: face evolution

Postby davidm on October 28th, 2018, 5:33 pm 

Larry Moran at his Sandwalk blog has always argued that chance and accident are the driving forces of phenotypes, not adaptationism. Not that he is the only one to say this, of course. I think he makes a good case. I still remember the online argument he had with Dawkins years ago about this. :-)
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Re: face evolution

Postby Forest_Dump on October 28th, 2018, 8:16 pm 

One of the things about shall we say extreme versions of sexual selection seems to be in the assumption that less attractive people assuming the same standards were in place long enough (100 generations? 1000 generations?), would be less likely to reproduce on that basis. However, by whatever standards that might exist, I think the less attractive folk also manage to get together just as much with each other and find a way through whatever other selective pressures they happen to face (so to speak). In other words, I kind of think looks were far less important than an ability to overcome other problems so that looks would have been left to more to factors related to chance such as the founder effect. When you are dealing with small dispersed groups, anyone who survived infancy would have become known within their group and among neighbouring groups for their various capacities and abilities so that a slight variation in nose or cheek shape would have been insignificant. I do, of course, acknowledge the adaptive value of different skin colours in different contexts but that is a different issue.
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Re: face evolution

Postby Serpent on October 28th, 2018, 9:31 pm 

Yes, exactly! If attractiveness were that big a factor, there would be nothing but beautiful people by now.
In fact, there were many other factors more important - health, wealth, availability, luck and love. The chiefest of those is availability: remember that for most of our prehistory and history, you married somebody from your same village, or the next village over. How many eligible partner would there be?
Even now, when so much - really, an unhealthy amount of - emphasis is placed on appearance, rather than skills or character, homely people still make lots of homely babies (and a surprising number of pretty ones!)
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Re: face evolution

Postby BadgerJelly on October 29th, 2018, 1:23 am 

Maybe just spandrels.
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