Ensign Steve

Um, yeah, I am. Are we expecting to somehow de-evolve those advances in the near future? We are talking about humans right? Hell, even the sterile have figure out how to replicate themselves, given our advanced technology.

tronvillain

Ensign Steve:
Ah, now that I look at what you were responding again to I see what you are saying. My response was in the context of our evolutionary history, not ranting about our "moral responsibility" to sustain and nurture reproductive success. In terms of nurturing reproductive success (if we wanted to do any such thing), homosexuals reproducing is probably better than infertile people reproducing anyway.

Doubting Didymus

Note that things can certainly be an unchanging part of your nature without being genetic. The usual example is the shape of your feet. I cant change the shape of my feet, and neither can you, but if you compare the feet of a person who has worn shoes all their lives to people who don't, you'll notice a marked difference: we're all deformed, and there's nothing we can do about it. However, we will NOT pass this trait onto our children, unless they also make a habit of wearing shoes.

There is evidence of a sort that homosexuality is genetic. A search on pubmed for "homosexuality twin study" yeilds about four or five recent twin studies into sexual preference, which consistently found a fairly weak genetic influence. Among identical twins that are men, (male and female sexual preference do not appear similar in their inheritance patterns), there is usually about a 50% chance that if one twin is homosexual, the other is also. Note that these twins not only share identical genes, but also identical developmental influences. On top of this, the worth of twin studies of this kind does not go unquestioned. I suppose you could call me agnostic as regards the influence of genes on sexual preference.

Traits that limit population growth by sacraficing the reproductive prospects of the individual are not known to exist. It just wouldn't work. If you posess a trait that causes you to have fewer children than the next fellow, and if you pass that trait onto your children, then the genes for that trait will disappear in the population, relative to the traits that encourage more children. The sterility example applies here because the argument my #4 addresses states that homosexuality limits the population by causing the individual to have fewer children. The example serves to demonstrate that should such a trait arise, it would be disfavoured by natural selection precisely BECAUSE it is copied into fewer members of each successive generation than its rival traits. As you point out, I don't think there is enough evidence to suggest that homosexuality IS a significant reproductive disadvantage, but if it were, as the 'population limiter' argument implies, then sterility would indeed be a relevant analogy.

It's almost certainly British.

Natural selection can indeed favour traits, and it does NOT select against traits that endanger the species. Natural selections only criteria is reproductive success. A moments thought illustrates why this is: Any trait that makes itself more likely to be over represented in the next generation will, by definition, be more common in said generation. Often, such a trait is one that aids survival, but it could just as easily be one that causes a detriment to the organisms survival, but simultaneously increases its offspring output. The tendancy in sea lions to battle rival males is an extremely unhealthy thing to have, but it persists in the population because that tendancy ensures that many more offspring are produced by that individual, who would all share it.

Now, having a species full of males all intent on brutalising each other to death might very well be terribly dangerous to species survival, compared to a species of sea lions who ignored the opposite sex entirely and spent all day breeding away, but natural selection simply doesn't care, and will go on favouring big violent sea lions with a miserable life expectancy so long as those individuals have a bigger than usual slice of the next-generation pie.

The point is, organisms that sacrafice their reproductive prospects for the good of the species will naturally be undercut by those that won't. As a result, the theories that hold up homosexuality as a species-helping population control just don't work.

If it's reproductively neutral (not survival neutral, as you suggested), then yes, it could enter the population through simple drift. If thats the case, however, then it is not going to serve any adaptive function.

abe smith

Uh.... I'd like to reiterate my standard assertion(s):
1. that there're probably a number of differing *kinds* of being-queer/homosexualities.
2. that in fact NOBODY can say with any certainty yet WHAT the causes/etiology of the homosexualities (plural) are, yet. (hence it's ill-advised to be waving the genetic assertion here, Folks.)

Therefore (not-quite QED) similarly to the arguments against "eugenics" (Hitler's et al for example): anyone's attempts to eliminate certain "disadvantageous/ 'bad' " human characteristics (by e.g. killing or sterilizing or otherwise eliminating from the gene-pool those (phaenotypes) who display those characters ) almost certainly WILL NOT WORK; because 1. ummm many such characteristics are recessive and are not known in their (silent) carriers;
2. the newest position about what we have been wont to call "genetically-determined" factors is, that the overt expression (in individual persons, and ALL THIS IZZ in single-packet individuals) of allegedly-"genetic" characters is frequently NOT-THAT-SIMPLE; but that the overt observable occurence of such characters results from a combination of "genetic" and "environmental" influences.
3. The whole field of "causes" (of anything! as Hume pointed-out) especially of 'human behaviours' is largely yet unexplored & as yet unknown; and for anyone to attempt to CONTROL that unknown area by legislation(as Hitler did; and as others even here in the USA have tried) is irrational and ineffective.

Discussing All-This here (which amounts then to expressing *opinions*) is of course lotsa fun and airs a bunch of possible theories; but not-too-much that is said at this time has much substantiability as to what really happens.

That Old Refrain is always haunting me: "We Don't Have A STAIN For That Yet."Hence a little healthy skepticism remains always in order.