Evolution and Modern Medicine.

Sexual selection can be entirely cultural, and very obviously subjective. Peacock feathers are an example. This is definitely “sexual selection,” and constitutes “beauty” in the eyes of the peahen.

Don’t get so postmodern as to deny the existence of subjective measures of value.

But my point is that things change far more quickly than evolution can keep up with. Sexual selection can be a very powerful driver, true. But it has to remain constant for more than a handful of generations to make any measurable difference. Physically, I don’t think it’s safe to say that I, my father, my grandfather, my great-grandfather, my great-great-grandfather, and my great-great-great-grandfather were all raised to find the same female features attractive.

Only in hindsight. How do you know that cheetahs 500 years from now (assuming they’re still around) won’t be slower than they are today?

Well, I don’t want to dwell on what was probably a throw-away line your post, but I think you may not realize how that line reads. You may not have meant it, but that’s what it says.

I don’t…and I never said they would!

I’ll accept this as a note to attempt greater clarity, but I also stand by what I said: “We are selecting for beauty.” At this moment in time, there is an evolutionary gradient toward greater beauty, in those countries where survival is otherwise relatively well assured. That could change in the next minute (i.e., if Putin and Obama mess up and exchange nuclear missiles. At that point, we start selecting for radiation tolerance instead.)

But there’s not. There’s no pressure that makes beautiful people reproduce at higher rates or that their offspring are better adapted (in the sense that more of them live). There’s also nothing preventing ugly people from hooking up and having kids either.

There doesn’t seem to be any significant evolutionary pressure on humanity at the moment as a whole; most anyone who wants a kid can have one, and have them survive to reproduction age.

Are you denying the very concept of sexual selection? The “pressure” is that pretty people are asked out on dates more than ugly people. To deny sexual selection at all seems to be a very radical redefinition of evolution.

Reproduction is not based on number of dates or even number of times a person has sexual intercourse anymore - thanks to modern birth control anyone can limit offspring, thanks to sperm banks and turkey basters and fertility specialists actual intercourse is not even required anymore.

Yes, “beautiful” people, however defined, might get more opportunities to reproduce than less attractive people,* all other things being equal*, but they may or may not take advantage of those opportunities and in the real world wealth, power, fame, or other factors may more than make up for less than wonderful physical appearance.

Well, there you have me: I don’t have concrete statistics. I’m gonna go with this, however: beautiful people have more sex, and sex is pretty highly correlated with reproduction. Sexual selection is at work when it comes to reproductive opportunity.

If you can demonstrate that beautiful people are more likely to use contraception than ugly people are, you would have a working rebuttal.

I see no evidence that we will be “trending” towards beauty. In fact, with the development/improvement of reproductive technologies, the ability of one to pass on their genes will become even more divorced from physical appearance.

I see at least some evidence, based on depictive art from previous centuries.

While Googling, I found this essay, which gives a nice yes-and-no balance, noting that some people say yes…and others say no.

(Warning: site has a noisy pop up ad, which you can click to close, but which is irritating.)

This is pretty much the best I can do: there are at least some real scientists out there whose opinions I can cite. There are other sites available, but, for the moment, allow me to punt.

Oops; I mis-answered. I agree with you that our ability to control our own genes will definitely lead to an entirely new regime of genetic change, driven by choice and less by differential survival. Whether or not it should be called “evolution” is just a semantics issue, and I wouldn’t know which way to go with it. Maybe “neo-evolution.”

I also agree with you, in that I would not want to say what we will be trending toward. I left my crystal ball in my other flying carpet!

(Hey, guys, at least give me credit for not thinking I can disprove Einstein with a simple thought-experiment!)

Why do we need to rebut something that you haven’t proven? I’m not even willing to accept that beautiful people have more sex. They may have more sex partners, but that doesn’t mean they have more sex.

If I really felt the need to project current trends into the future, I’d say the human species is going to become browner.

If you disagree with it, you ought to say why. Just dismissing it is shallow debate technique. Yes, you can, in all validity, say, “Cite?” and let it go at that. But that doesn’t really add anything to the dialogue.

I have admitted from the first that I can’t prove it. I did, however, provide a cite.

Well, okay. Whatever. There are certainly statistics out there showing that the average height of people in the industrialized nations is increasing. Much of this is the result of health care and better nutrition, but some of it could be sexual selection.

Are you willing to accept the principle of sexual selection in evolution at all? We’ve had one participant here who didn’t.

Agreed. More properly, that’s the direction of the trend at this moment, but it might change at any given moment. I don’t want to be accused of projecting the future, only of suggesting there is a differential gradient at this moment.

(The earth’s population is growing…pretty much always has been…but that doesn’t prove it will continue to do so forever. Even the most pervasive trends can be reversed.)

Well, here’s a highly regarded scientific journal:wink:

I think you’re misunderstanding how this works. Selective pressure would be some sort of effect on the population that would cause one group’s offspring to be more successful than another’s.

A classic example is the peppered moths. In England, prior to the industrial revolution, peppered moths were a sort of mottled white to better camouflage themselves against the whitish tree trunks. There were occasionally very dark variants that were pretty much dead meat for birds, as they stood out against the tree trunks.

Enter the industrial revolution. Tree trunks get sooty, white moths stand out, dark ones don’t. Over time, the darker variant is the most common one. Since better environmental standards have been introduced in the 20th century, the light ones are taking back over.

The presence or lack of the soot on the tree trunks is an evolutionary pressure causing natural selection. Those same moths though, tried to hook up with the prettiest other moths they could; that’s just sexual reproduction.

Like I was saying, there’s NO evolutionary pressure making pretty people be selected versus ugly ones. I don’t know what pressures there are on people, but pretty/ugly isn’t one of them.

You haven’t answered the question: do you agree that there is such a thing as sexual selection? Your answer makes it seem that you don’t accept its existence at all, rather than only rejecting it in the one instance of human sexual selection on the basis of attractiveness.

Do you agree with the traditional explanation for the peacock’s tail, and other features, via sexual selection?

Sure, sexual selection exists, but in nature, the traits that are typically sexually selected for are proxies for health, freedom from parasites, vigor, access to food, etc… Generally speaking, the creatures with those attributes are going to have more successful offspring, etc… because of what the traits signify.

For example, all male peacocks have the genetic makeup to have the big tails. Some may have genes predisposing them to bigger or brighter tails, but ultimately the thing that makes the difference in tail size is that the ones with the biggest tails are stronger, faster, smarter, or just lucky enough to have adequate food. So they mate and their offspring are hopefully stronger, faster, smarter or luckier as well, and grow big tails, and are more successful than the other smaller-tailed peacock’s offspring.

They’re not being selected for bigger tails genetically, but rather to be stronger, faster, smarter or luckier.

That’s the fallacy that you’re suggesting is happening in people- that we’re being selected as a population to be better looking, and that’s just not the case because the pretty/ugly indicators just don’t actually indicate anything now that we’re civilized- just about everyone has adequate access to food, and the offspring of ugly people aren’t disadvantaged in any evolutionary way that would cause them to be less numerous or successful than pretty people’s offspring.

To demonstrate that sexual selection is happening in humans, you could study it in a couple of different ways:

1: first, you’d need some way to objectively quantify “beauty”. Not easy, but doable. Then you could measure reproductive success in beautiful people vs not beautiful people and see if there’s a difference. You would, of course, need to control for lots of other factors, such as socioeconomic status. Rich people can pay to make themselves more attractive, after all. This would be the bare minimum. If you want to argue that sexual selection is happening, you have to observe that it is happening.

2: once you’ve quantified “beauty”, you could do a genome-wide association study looking for specific genetic markers that are highly associated with high “beauty” scores. This would identify genes and alleles that contribute to the beautiful phenotype. Then, you could assemble population genetic data and look for signatures of selection in the surrounding areas of the genome (synonymous vs non-synonymous substitutions, for instance). This would have the added advantage of showing that sexual selection has been happening long enough, and acting consistently on the same alleles, to have made an impact on the human genome.

I don’t think I agree with this principle.

However…it could apply to human beauty, as many illnesses are disfiguring and unlovely.

Well, are all evolutionary studies done on a “genome-wide association study looking for specific genetic markers?” A lot of evolutionary science is done observationally, without such in-depth technology. Darwin did most of his work without access to genome-wide searches for genetic markers: he observed physical traits in pigeons, worms, and other animals.

You’re right, of course, the science could be done this way, but it isn’t the only way.