Holy jeez, I have a lot to reply to...
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Originally Posted by raveneye
Actually C4, one could argue that sexual selection is currently having a greater evolutionary effect than in the past because it is no longer held back by natural selection, at least in developed societies.
Anybody want to suggest human traits that probably evolved by sexual selection? Here are some possibilities:
--many racial differences in facial features (no adaptive value, however certainly important in sexual attraction)
--sex differences in voice pitch
--sex differences in size, muscle mass, hair
--fat content in breasts in women (no adaptive value, but apparently important in sexual attraction . . . . )
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Not a chance. People with small breasts don't reproduce? People with less desirable facial features don't reproduce? That may be the societal preference but these people still reproduce and thus the genepool is not directed regarding these traits, making any sexual selection unrelevant with regard to them. Also, vocal differences and body structures are a result primarily of natural selection. Voice so the genders can recognize male from female (and thereby recognize possible rivals / mates). However while people may have a sexual preference for a certain body type, others still reproduce.
I think some people are confusing sexual selection with sexual preference. Just because you would like to have a mate with certain traits does not mean that those traits cause sexual selection. In order for sexual selection to occur, the other (negative) traits must correlate with less reproduction due to the inability to find a mate. Like I said previously, very few people are so undesirable that they can't find anyone to have kids with. This happens primarily because our genetics tend towards a 1/1 male/female child ratio and our society is monogamous.
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Originally Posted by Charlatan
You also need to remember that things like modern transportation (i.e. stream trains to the airplane and automobiles) have drastically effected the diversification of the gene pool.
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This can be a correct statement, but I believe you have the wrong idea. Interbreeding among populations may cause genetic diversification at the level of individual populations (eg. an isolated tribe), but as a species it actually causes a sort of averaging-type effect which reduces diversity. Introduce enough of the rest of the world's genepool into that one population, and soon enough that tribe will be a lot more like everyone else.
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Originally Posted by wilbjammin
People do look for desirable traits, such as symetrical faces, good hygene, etc. But, in general, fitness is not something that comes in play as much as it used to because it is not necessary. Look at those suffering from bulemia and anorexia or extreme obesity that find partners. Now there is a larger variety of what can be found that is survivable for humans, so the umbrella is getting larger.
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Physical fitness is not what I meant. I meant fitness in the sense of reproductive success. In this sense, fitness is defined as and increase in adaptation to the environment, as brought about by genetic change. Therefore, a greater degree of fitness causes those creatures to survive (be "naturally" selected) and mates look for the traits that are a sign of fitness (hence they are "sexually" selected).
However, this is exactly my point that sexual selection really does not come into play. Even the seriously ill find partners.
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Originally Posted by Yakk
Family planning is a selection criteria.
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A sexual preference. It does not cause sexual selection.
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Originally Posted by Yakk
Stable societies that aren't awash in mass violence is a selection criteria.
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In the sense that genocide erases populations, yes. But this is a human-induced, conscious event. I believe the issue at hand was whether evolution was still naturally occurring, and I do not consider warfare to be a natural event.
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Originally Posted by Yakk
First, you are assuming a very strong correlation between parent and child fitness, for two seperate pools to form.
Second, people change. At 13, that eventually supremely intelligent, ultimately attractive and great personality person might knock up the ditzy cheerleader, or be knocked up by the football quarterback.
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Well, the assumption is that the parents traits will most likely be passed on to the childern, but yes, it's not so simple. That's why I said you'd have a tough time defending that position, and I didn't really try to.
Lastly, I agree that soon enough we'll be genetically engineering ourselves at a rate millions of times faster than what would ever happen naturally.
Whew... I like it when you guys make me think. It's so stimulating.