posted 11-06-98 01:13 AM ET        

Octopus: (defending the idea that natural selection would remove homosexual genes) Natural Selection operates on individuals, not species. ("There's no such thing as group selection" as my Comparative Psych professor used to say). If possessing a trait does not make the individual who possesses that trait "more fit" than other members of his or her species, then that trait will not be selected for. Yes, it helps the species as a whole, but that is not how natural selection operates.

You must have miss-heard your professor. You have it exactly backwards! A quote from my biology book: "Although it may seem obvious, it is important to keep in mind that individuals don't evolve; populations do" (p.541).
Starr and Taggart, Biology: The Unity and Diversity of Life, 5ed.
California: Wadsworth Puplishing Company

posted 11-06-98 01:15 AM ET            

Fact: we have no knowledge of any environmental factors that influence sexual orientation. There has been extensive research done on this topic. Researchers have examined parental relationships, childhood sexual experiences, peer relationships, dating experiences and so forth. None of these things have been linked to homosexuality.

I have references if anyone is interested.

posted 11-06-98 02:00 AM ET            

1) Within any population, there is natural variation in heritable traits.
2) Some of these traits will make an organism more "fit" in its environment. Anything that increases the presence of an individuals genetic presence in succeeding generations is considered "more fit". Great strength, great intelligence, numerous offspring, and effective parenting are all different techniques that organisms have in the past used with good effect to increase their fitness.
3) Conversely, some of these traits will make an organism less "fit" in its environment. An example of a trait like this would be a digestive system unable to metabolize any of the food available in the environment -- the organism would be likely to die before it reproduced.
4) Since those individuals with greater fitness will pass on the heritable traits that contribute to their fitness on to their offspring, those traits will become more widely spread in the population (the "good" traits proliferate while the "bad" traits die off).

That is pretty well accepted as the mechanism by which evolution takes place. The definition of "fitness" is a bit hokey because it has to be. Strength, intelligence, etc., may all seem like good ideas, but they do not necessarily translate into increased fitness, which is why evolutionary problems are frequently difficult to solve (it is hard to figure out what the fitness criteria are).

NOW, the thing to notice in the above discussion is that "populations" are mentioned in the above description in only two places: "varied individuals make up populations" and "populations tend to be made up of individuals with high fitness". All the ACTION takes place at the individual level.

Here is an (admittedly contrived) example: Imagine a person has a freak genetic mutation that makes him thousands of times more intelligent than average. A side effect of this particular mutation is that this person's hormones are somehow off-balance during his development, and as a result is completely unable to produce any sperm cells. This person, with his incredible genius, invents numerous devices to make life easier for everyone. Now, lets review: this person is a HUGE benefit for the population as a whole. This person's genes will NOT be represented in the next generation, because he is completely unable to have ANY children (at least by traditional means). This pattern of genes will NOT increase in prevalence in the population.

The mechanism of natural selection operates on individuals. The phenomenon of evolution via natural selection is observed in populations. Do not confuse cause and effect. Being "naturally selected against" is a VERY personal experience, since (at least in most cases) it means you are dead.

This is what I mean by "there is NO SUCH THING as group selection". It doesn't happen. Selection happens on individuals.

posted 11-06-98 06:04 AM ET            

I just don't understand how someone can say "you'll be gay, and you woun't" just by looking at their genes.

posted 11-06-98 10:15 AM ET            

The trick is that usually no one specific gene codes for one specific trait. Usually it�s a bunch of genes working together to produce a trait. And even if a gene coding for a specific trait is present it isn't always activated. It may need to be turned on by its environment. The gene may also be recessive. What if it is the mothers that carry the genes for homosexuality and create homosexuals through the influence of hormones while the child is in the womb? There is some evidence that this happens. A German researcher Gunter Dorner manipulated a fetal rat's exposure to male hormones, "inverting" its sexual behavior toward rats of the other sex. Similar studies have been done with sheep.

Some statistics:
An identical twin whose brother is homosexual is homosexual 54% of the time. If the brother is a fraternal twin the chance is 22%. Any single person picked at random from the population has a 3-4% chance of being homosexual. This suggests genes have an influence. But since half of identical twins differ this isn't the whole story.

It is still not known why people are homosexual, but a lot of research has been done and more is being done. So far no environmental factors have been found that influence homosexuality.

posted 11-06-98 12:28 PM ET            

The only candidates I have seen so far that make any sense to me are "the genes that encode homosexuality are very close to the genes that encode some other trait. The benefits of this other trait are so great that they outweigh the negative effects of homosexuality. So, the price that a person pays for having some homosexual offspring is offset by the benefit of their other children having this wonderful trait. Nobody has postulated what this other trait or traits might be.

posted 11-06-98 01:30 PM ET            

Most of the common traits that are harmful to humans that have survived through the ages, can attribute their continued existance to several factors.

1. The bulk of them do not effect humans until the later stages of human development. ie. late twenties and on.

2. We as a people used to start giving birth to the next generation by the age of 12.

3. Thus the combination of 2 & 3 allow the aforementioned traits to survive.

posted 11-06-98 02:34 PM ET            

To answer your question on CF...CF gene is on Chromosome 7. It has been shown that the people who were Cc (one "good" gene and one "bad" gene) can survive cholera better than CC's could. (One study actually dug up bones in an ancient Hungarian graveyard and checked the genotype of those who survived one of the worst cholera outbreaks in history. The vast majority of those surviving were Cc.) Hence, they survived in the European area better. In the African area, where cholera is not common, finding any people, even Cc's, is very rare. Only in populations exposed to cholera do you find Cc's and those unlucky enough, cc's. The ones with cc did not survive to father/mother children. The gene survived based on the Cc's being, using Octopus's words, "more fit."

Sickle cell is the same. The Ss were better able to fight malaria, hence they were "more fit." The ss's did not survive. In regions malaria-free, like Norway, the s gene is very (emphasize very) rare, because there was no advantage to being heterozygous. In Africa, being heterozygous was a distinct survival advantage, hence the gene survived generations. The ones unlucky enough to be homozygous "s" were mourned as they died at early ages, but the gene survived through the other children.

Hope this helps. BTW, another argument in the previous thread was the discussion about the intelligence of the population as a whole. I would argue that if perhaps the intelligence as a whole has gone up (something I am not so sure of) it would be due to a very small percentage of the population. It appears that our (referring mainly to the first-world) civilization is creating a two-part society. One part being highly intelligent and the other part increasingly average or worse. How many 9 year olds can play computer games or program VCR's but do not know math tables or how to read? Perhaps I am jaded by the population I am exposed to at a teaching hospital, but many I see know how to use cell phones, VCR's, pagers, calculators, but are unable to read or do math. Reminds me of a story (Cannot remember what story -- maybe someone could help me) where everyone was dependent on machines and the "highly intelligent" people who ran the machines. For some reason, these "HI" people died off or left and the rest of the population was dependent on these machines which they did not even know how to repair. My argument then is that for the majority of our population, intelligence has not risen, but has decreased.

Hope this helps with the genetics of CF and SC.

MedIntern

posted 11-06-98 05:24 PM ET            

The reason that your "they don't need to take care of their own children, so they can help everybody else" theory doesn't make sense to me is because the people who get the benefit in that case are precisely those people who DON'T have homosexual traits. Therefore, being non-homosexual is the trait that is going to be selected for in an evolutionary sense.

posted 11-06-98 07:03 PM ET            

a * (e**(x*b)-1) * (y**c)

where a, b, c, are constants and x is the percentage of heterosexuals and y is the percentage of the homosexuals. Just playing with the numbers a little, with a=0.01, b=0.1, and c=0.5(square root of y, that is), you get a pretty sharp peak at y ~= 5%, with half the benefit at y ~= 0.5% and y ~= 18.5%. This is fairly reasonable given reports on the actual percentages of homosexuals in the population(3%-10% depending on who you listen to, IIRC).

This type of benefit has a peak at some fixed proportion of homo to hetero sexual.

posted 11-06-98 08:13 PM ET            

Concerning Hardy-Wienberg: I had previously read about this in an introductory evolution book and it simply stated that it was used as a starting basis to measure change in a population. Also its application shows how recessive genes will stabilize in a population. I looked it up in a college text and I have to admit that I cant completely follow it with a cursory reading. It will have to wait for the end of this semester so I can devote some time to it. The book I am looking at is Evolutionary Biology by Douglas Futuyma. "A deleterious recessive allele is seldom completely eliminated by selection, because when it is rare it occurs only in hetrozygotes, in which it is "protected" by dominant alleles. Natural populations should therefore have many deleterious recessives in low frequency, as is in fact the case (p. 315)." He also shows that if a recessive gene is advantageous when heterozygous it will increases in a population even if the homozygote form is disadvantageous.

posted 11-07-98 12:15 AM ET            

I'd like to personally thank AltoNido for understanding that the benefits that we need to talk about in Natural Selection terms apply to individual and families, NOT populations. (or at least it sounds like you understand).

AltoNido: I would hardly say that homosexuality "did not confer a negative effect". Maybe I'm missing something that the rest of you see, but failing to mate consistently with members of the opposite sex is going to seriously reduce the probability that each of those matings produces an offspring. This is an obvious disadvantage!!! (at least it would seem so to me). Now maybe the disadvantage is outweighed by some other advantage, and maybe there are mitigating traits (like living heterosexual lifestyles despite true orientation), but it seems to me that it should have (at least some) negative effect.

Your point about helping siblings is a good one, but (as I believe I said before, possibly in the other thread) I think that it might be a tough stretch to explain why a homosexual sibling is SO much better than a heterosexual sibling that he makes up for the deficit of not producing any children of his own. Could this be the explanation? Certainly, I'm just reserving judgement at this point because I'm not overwhelmed with confidence in this answer. I would love it if others would try to explain this seemingly paradoxical situation.

MedIntern's do explain how fitness-reducing traits can survive in populations. The same could be true for homosexuality (again, as I've said before) but it seems to me that homosexuality is generally a bad idea (in the evolutionary sense), so what is the good idea that's almost the same thing as homosexuality (like cholera resistance is to Cystic Fibrosis)? However, I suspect that a LOT of homosexual people would be offended to have their sexual orientation compared to something that is considered a medical disorder. (but that doesn't mean it's not true).

Moon Rat: I believe that I probably have been a bit too forceful in my positon, but I think that's because I got the feeling that nobody was understanding my point about "no group selection". I still get that feeling. There are some viable explanations, like the CF analogy, but I really do think that most homosexuals would resent having their sexual orientation compared to CF and similar conditions. When I originally started posting about this, I essentially said "this doesn't make sense, please show me where my analysis is wrong". I haven't seen much of that. I will accept that homosexuality could be linked to some other trait, it just isn't as "clean" an explanation as I had hoped for. If anyone has any better explanations, I'd still LOVE to hear them.

posted 11-07-98 02:33 AM ET            

(note: lemmings don't actually do this, apparantly the whole idea is some sort of Disney propaganda or something, but it works for the example).

Lemmings are widely known for mass suicide.

Hypothesis: large numbers of lemmings, in times of low resources, recognize that an abundance of lemmings will deplete resources. They make the analysis that it would be better for all lemmings if a whole bunch of them got together and jumped off a cliff to their watery demise, leaving resources enough for those lemmings who stay behind. This (still part of the hypothesis) is an evolutionary trait that allows lemmings to survive in a highly variable environment.

Action: All the suicidal lemmings leap off the cliff, effectively removing themselves from the population. The lemmings who were less inclined to kill themselves now thrive.

Result: In the next generation, there are no descendents of suicidal lemmings (I killed them off a few sentences ago) and lots of descendents of non-suicidal lemmings.

Later On: Times get tough again. This time, the vast majority of lemmings are genetically predisposed to NOT jump off cliffs, like their parents, and their parents before them (remember, all the lemmings predisposed to jumping off of cliffs died and didn't reproduce). Therefore, no mass suicide.

Proof: All statements following the premise are logically sound. The conclusion is false (it conflicts with the "known" fact that lemmings engage in mass suicide). Therefore, the hypothesis must have been wrong (proof by contradiction) -- i.e. mass suicide is NOT an evolutionary trait of lemmings.

So, why didn't it work? It seems like it makes sense on the surface -- make room for those who CAN survive instead of dooming everyone to a slow death by starvation. It certainly seems like a good move for lemmings as a whole... BUT! Natural Selection doesn't work on the population of lemmings as a whole -- it operates on each and every individual lemming. Since those lemmings which had the trait (even though it is a "desirable" trait for lemmings as a whole) did not pass it on to the succeeding generations, the trait did not become dominant in the species. The species did not evolve to include this trait in itself.

Okay, what does this have to do with the homosexual shaman? The hypothesis put forward by JB (and possibly others) was that the homosexual shaman, since he wasn't busy raising his own kids, can help everybody else in the tribe. Notice, however, that this means that there is a sharp decrease in homosexual shaman genes in the next generation. This ALSO means that the homosexual shaman's parents got short-changed. The homosexual shaman contributes some benefit (I'll call it s) to every member of the tribe. Each heterosexual offspring a parent has contributes a benefit (I'll call it c) to his or her parents (since they will be passing the genes down to the next generation). Therefore: the family with no homosexual shamen and n children gains s * (2+n) + c*n (the shaman's benefit to both parents and each child, plus the benefit from each childe). The family in the same tribe that actually has the homosexual shaman in it gains s*(2+n) + c*(n-1) (the shaman's benefit to both parents, himself, and his siblings plus the benefit conferred by each heterosexual sibling). By simple subtraction we see that the family without the shaman has 1*c more total fitness than the family with the shaman. The family with the greater total fitness is the one that has the genes that are Naturally Selected for.

Now, in order for the homosexual shaman theory to work out, the homosexual shaman needs to contribute MORE fitness to his own family than to other members of the tribe. This is basically what AltoNido put forward.

posted 11-07-98 05:59 AM ET            

"we are not talking about a family, we are talking about a tribe" This absolutely confirms that you are not understanding my point. I am wondering if this is worth the effort anymore.

It is one thing to have someone disagree with me. I can accept that and debate them, or change my opinion if I am wrong. This seeming lack of understanding of my argument, however, is infuriating. Does ANYBODY at least understand what I'm TRYING to say?!?!

The explanation that homosexuality is a recessive trait linked to a different trait which is advantageous seems somewhat reasonable. However, it is not a very satisfying answer, so I don't consider the issue closed, at least as far as I'm concerned. My personal suspicion is that genetics has very very little to do with homosexuality.

posted 11-07-98 01:26 PM ET            

In putting my formula forward(which you are correct to point out as arbitrary), I was pointing out a failing in your formula(see below for an explanation of my formula and where it comes from). In positing a 1/x benefit from a homosexual population, you ignore the form(mathematically speaking) of this benefit(how it is dependent on the proportion of the population that is homosexual) and what the effects of certain values of benefits would be. For certain values of x and k in your formula, the y/x term is quite large(for example, if x=0.01 and k=1, the benefit from homosexuality completely overwhelms the benefit from the heterosexual children(note: I am note suggesting it is this dramatic)).
It is important to look at a situation where, for example, k=1 and x=0.9. In this case, your formulas are y + 10*y/9 and (y-n) + 10*y/9. Assume two families(again, in the nuclear family sense) with 8 children each, one with 1 homosexual child. With this, the (y-n) term is 7. Simplify the formulas and you get (19/9) * 8 = 16.89 for the family without homosexual children and 7 + 10*8/9 = 15.89. Now, granted, the family with the homosexual child gets less of a benefit, but compare to the total benefit of 8 for a totally heterosexual population. Now, remember, in such a small group(maybe 10-20 nuclear families), the different nuclear families are sharing a large amount of their genes, so even the family without homosexual children stands a good chance of carrying the gene. And, yes, my figures are arbitrary, but are simply meant to show that for some values of your benefit constants it is possible to gain _very_ significant benefits. Combine this with your false implicit assumption that the family without homosexual children does not have the gene present(though it is possible it does not), and you should be able to see how such a trait could evolve. And yes, while families with homosexual children don't get as much benefit as those without, it is possible that the benefit to all is significant.
Also, while it might seem that since the families with homosexual children would be at a disadvantage, it is important to remember that at this point in our evolutionary history we would have been in the hunter gatherer stage where the groups of families we are talking about were _very_ close to each other genetically and therefore probably as a whole only one or two mutations away from homosexuality. Also, because it is most likely a minor advantage, it would spread to the general population as a recessive.

--

One point that hasn't been raised in this thread yet. If homosexuality is genetic(which I don't consider proven either, though there is a pretty good case for it), it's probably been with us for a _long_ time(assuming you accept evolution). Goodall, Fossey, and others have reported homosexual behavior in the primates they study, so it would be reasonable to assume(I think) that it would have been present in a common ancestor.

--

As to why I chose the form I did for my arbitrary formula, look at it this way.

posted 11-07-98 03:11 PM ET            

I maintain my point about homosexuality not being a benefit (it still seems to me to be an evolutionary liability rather than an asset). The "concession" above will permit that homosexuality won't be stomped out because it is "hiding" behind other traits, but I still don't see how it can be beneficial. When I talk about families, I mean "any group with a siginificant cross-ownership of genese". In my formula, there is an implicit assumption that the benefits are roughly linear (I don't think that's entirely unreasonable, given that they are based on numbers of individuals in the population) and also that the benefit of having a heterosexual child that reproduces is a pretty hefty evolutionary benefit (greater than any "helping" effects). However, even with your huge helping effect, you concede that the family without homosexual children is better off. Natural Selection does not compare between an individual/family and some other strategy that theoretically exists, it compares between individuals that actually exist in this environment. The differential benefit goes to the family with no homosexual offspring, so that is what is selected for. Seems like a bad idea for the species? Maybe so, but having this trait means a net reduction in fitness compared to the family's competitors (the other families), so they get selected against.

-----------------------------------------

I think I've been rehashing my original point for a while now. Maybe someone wants to think about something else? How about this:

In most other species it is obvious when the female is fertile (examples include the area around the genetalia swelling up and turning red). Humans do NOT do this (unless you guys all know something you're not telling me). This trait DOES seem to have dominated our population compared to our close genetic neighbors (other primates). I would therefore postulate that there IS an evolutionary reason for it.

So, what's the reason? My first suggestion would be that removing the biological clues about fertility serve two purposes: 1) sex becomes more recreational (since you've got to do it a lot more often in order to "hit the jackpot" and fertilize an egg, which would tend to increase pair bonding between a man and a woman, creating a stable family for their children, and 2) It is a "sneaky" trick in females to rope males into a more monogamous relationship -- since the male doesn't know when the female is fertile, he's got to guard her almost 100% of the time against other suitors, meaning he's got no time to fool around with other women. (note: I've got nothing against monogamy, it's just that the "lots o' sperm" feature of males tends to make polygamy look like a good idea, in an evolutionary sense. (note about the note: I've been arguing in the other thread that number of offspring isn't as important in humans as quality of parenting, so the females of the species seem to be doing us a big favor here)).

posted 11-07-98 03:38 PM ET            

Hh -- So he's heterosexual.

Now the first generation of offspring(all four combinations).

Hh X HH -> HH, HH, Hh, Hh -- All heterosexual, half carrying the gene, still nothing to select on

You won't have any homosexuals until at least the first Hh X Hh pairing, by which time, there are plenty of carriers of the h gene. Even without a benefit, homosexuality is there to stay(because Hh people, while at some disadvantage, will still be producing offspring -- and this disadvantage can only manifest itself if they mate with another Hh person), and then only in a slight reduction in the next generation's offspring. With a benefit, it helps the group as a whole(with the h gene in the pool), to outgrow other groups(without the h gene in their pool).

As to the reason I feel the benefits/detriments of homosexuality would not be linear with population, it is not just the presence of homosexuals we need to look at, but the interactions they cause/prevent.
For example, for two people, there is only one possible way to pair them. For four, their is maximum possible of 3. For 6 the maximum is at least 9. This doesn't look linear to me.

From a purely genetic standpoint, I don't really have a problem with identifying homosexuality as similar to CF or sickle-cell. On a social/emotional level, yes, they are diffferent, and I would have a problem with identifying them as similar.

--

posted 11-07-98 05:36 PM ET            

Sexuality is the same issue. You can break it into homosexual and heterosexual, but that is an oversimplification, because in between are bisexuals and people who may prefer one gender, but can be attracted to the other.

Also, homosexuality does not seem to be directly genetically hardwired. If it were, then all identical twins would have the identical sexuality. As with most things, sexuality is the product of the union of nature and nurture. Environment plays a significant role. Height is a good example here too-since the middle ages, people have grown considerably taller on average, at least in the developed world. The reason is not selection, since selection for height is not particularly strong. Instead, people today eat better, and this makes them grow taller.

Why is all this important? There seems to be some correlation between homosexuality and creativity. Now, what I'm saying here is not that the "homosexuality gene" causes creativity, and homosexuality is thus adaptive. My guess is that homosexuality is actually more likely to show up in creative individuals, or at least in the sort of person who is willing to question society and tradition. It is easy to see how these traits could be adaptive. Only when very many of the genes that increase creativity or rebelliousness are present _and_ the person is exposed to certain experiences does he/she become homosexual. As for uncreative homosexuals, they were just products of their experience, and they are possible because there is only genetic correlation between genetics and homosexuality, and just as not all people with "homosexual genes" are not homosexual, not all without are heterosexual.

You may not accept my idea that homosexuals tend to be more creative, and I really can't support it, but I would also argue that they tend to be less tied to mainstream culture, and while you could say that was caused by their homosexuality, it's just as easy to say it was the other way around.

posted 11-08-98 01:14 PM ET            

1) The gay gene(s) is recessive
2) The gay shaman produces no offspring (that is, he is in fact "sterile")
3) The gay shaman helps his siblings/parents/etc
4) Being Hh or hH gives you no disadvantages

The people who support this theory state the following:
(1)+(2)+(3)+(4)-> One of the gay shaman's (hh) must have a parent that is Hh/hH. This means that if he has a lot of siblings, at least one of them will also be Hh/hH. Since the gay shaman helps these siblings, they are more likely to survive, thus making it possible for them to pass on their genes to their offspring.

This seems very probable at first. But if this is true, then we would see very many other sexual dysfunctions that are as common as homosexuality (say 5%). By this I mean dysfunctions that make production of offspring impossible, while at the same time they do not cause the "shaman" to be a total invalid.

For example (assuming that a shaman could be either male or female), we would see that about 5% of all women had no wombs/ovaries etc. We would also see about 5% of men having vastly deformed penii of being impotent from birth (thus making intercourse impossible -> sterile). There ARE of course women/men with the above noted sexual dysfuntions, but they are very rare (say 1 in 10,000 or so).

These individuals would have been just as qualified for the shaman role as gay individuals (a shaman doesn't realy need a womb, ovaries or an erect penis to tend to the children). Yet there are very few individuals with these traits. Why?

If you ask my humble opinion, it is because sterile offspring (even if they are incredibly good at helping to raise children etc) are NOT as good as fertile offspring in passing on their genes. Most likely the explanation (IF homosexuality is genetical) is one of the following:

1) Complicated rescesive (involving many different genes), where the heterozygots do not have and "bad" traits.

2) Dominant (that is both Hh/hH/hh ARE homosexual), but the social rules of sexual conduct "force" the gay individuals into a heterosexual partnership, thus producing offspring that may (or may not) be gay.

posted 11-08-98 11:12 PM ET            

The reason the Shaman theory doesn�t work is because we just don�t know that much about evolutionary genetics. The Shaman theory is part of a much larger problem, the problem of the altruistic gene. "Just how is altruism selected for in the first place?" An example of an action that is thought to be altruistic and genetic is the warning call that some creatures make when they see a predator. How can a gene that increases the fitness of a group but decreases the fitness of the individual be selected for? Evolutionary theory has a lot of leads to this problem but no sure answers yet. I suspect that when science finally comes up with a genetic understanding of altruism we will know whether the Shaman theory is workable or not. Until then it is a "just so" story. (Not that it might also be the truth.)

posted 11-08-98 11:17 PM ET            

A study done in 12 of the largest US cities showed that the percentage of men identifying themselves as gay was 9%. This is compared to 1% in rural areas.

A study of the biographies of 1004 eminent people found homosexual and bisexual people over represented (11 percent of the sample), especially among poets (24%), fiction writers (21%), and artists and musicians (15%).

posted 11-10-98 10:10 PM ET            

I haven't read any books dealing specifically with the evolution of animal behavior. Do you know of any popular books that look at complex animal behavior from an evolutionary viewpoint? (Hopefully with reference to scientific studies) The book I have now mostly sticks to genetical analysis. So it is about melanic moths and fruit fly features. (no complex behavior)

posted 11-10-98 11:44 PM ET            

Thinking in an evolutionary perspective is fun because you get to exercise different analytical muscles than usual. Animal behavior is fun, because you get to learn about all of the wacky things that animals do, and all of the cool experiments that psychologists have dreamed up over the years. Comparative Psychology was the best class I had in college (and I'm an Electrical Engineer ).

posted 12-02-98 10:12 AM ET            

As for the nature/nurture discussion, I've got sth. more to add.

The fact that children raised by homosexuals tend to be heterosexual does not prove that homosexuality is a genetic trait. (Quite the opposite, if the child in question is the biological offspring of a homosexual...)

There are other factors which may affect people, aside from the family. In a recent study, it turned out that the percentage of homosexuals was higher in Finland, than in Sweden (as opposed to the (in Finland) popular myth, that Swedish men are homosexual weaklings, hehe...), and it was theorized, that there was a connection between homosexuality, and how "macho" a society is. It certainly fit the Sweden/Finland case, and according to the study, it seems to fit other countries, as well...

I find it an interesting theory, and I guess we may be seeing more of it in the future.

posted 12-02-98 02:19 PM ET            

I think a 'gay shaman gene' would disappear from the genepool, even if it was a recessive gene. But it depends on how much the survivability increases with the extra care a shaman would invest in his relatives compared to the survivability of the shamans genes.

In an attempt to show why I think there can be no shaman genes i have divided it up in cases. I have assumed homosexuals get no children.

hh: A person with two homosexual genes will usually not have any children at all. No spreading of h genes.

Hh: If with a Hh partner 25% of offspring will have homosexual genes. Only 50% will have chance of spreading h genes to the next generation, but 75% will have chance of spreading H genes.
If with an HH partner, 50% of offspring will have chance of spreading h genes, but 100% will have chance of spreading H genes.

HH: A person with two heterosexual genes will get 100% straight children, disregarding if the persons partner have homosexual genes or not, since his genes are dominant. All children will be able to have children in turn and spread the H gene.

In none of the cases the h gene would continue to the next generation with the same probability as the H gene. If such a h gene would exist it would become more rare with time and probably finally cease to exist.

If you think the above reasoning is wrong, please tell me.

posted 12-02-98 02:42 PM ET            

Even if a shaman in the family would mean higher survivability to his siblings children, that would probably include both the ones with Hh and HH. The shamans parents would have to be Hh both. That would mean that 25% of his siblings would be HH and only be able to pass on H genes. 50% will be Hh and have the same chances that the H and the h gene gets passed on. The probability that the H gene is passed on to the next generation is STILL larger than the probability the h gene is passed on, even with a shaman in the family!

posted 12-02-98 02:50 PM ET            

From my personal experence I have found that a large number of my male partners in the 80s were "hapily maried men" complet with kids. You cannot discout "traditional peer presure" within society that basicly stresses that men should be Maried and have kids., to the extent that it was actualy a unwrinten rule prior to WW II in (for example) the USarmed forces that if an officer wanted to be promoted beyond Lt/Cpt they had to be maried.
(even today their are a number of "couples in the US Millitairy who are "couples" maried gay/lesbian couple using the other as a "sheild" untill they finish their curent TOD without being forced out"

Beyond that, retailers sutch as Wards had (untill roughly the mid 60s) a writen policiy that it would neither hire nor promote any unmared men/women as managers.

Also their is the "Grandparet" syndrome keeping presure on us to have at least one
child to "carry on the family traditions"
(my mother in particular keeps asking when I am going to find a " a Lesbian who wants to be a good mother")

thus societal presure may "force" reproduction when genetics would seem to preclude it.

posted 12-03-98 02:53 PM ET            

2) antaganistic pleiotropy
The gene has some positive effects too.
This is the majority of the arguements here.
however they can be divided into two catagories. a-individual benefit
certain genes which have the side effect of predisposing to homosexual behavior increase the individuals fitness
for example lets say that there was a usb (unusual sexual behavior) gene, some would become homosexual but others would go around and have lots of kids with lots of people so the average # of kids would increase.
b- group selection theory
this basically says an Hh X Hh family would be better than a all hetero family
Assume a average hetero has 2 kids on average but if they have a homo sibling they have 3 due to additional help hunting, etc..
4 hetero kids=8 grand kids
3 hetero, 1 homo(Hh X Hh)=9 grand kids
so Hh people have a slight benefit

Note: this only works with violations of Harvey-Weinberg equilibrium i.e. tribes that tend to mate among themselves

Finally there is the massive environmental effect on something as complex as sexual behavior which helps mess up all genetic models.

posted 12-03-98 11:42 PM ET            

Don't forget that for basically the entire time that the human species has been esistant (ignoring this trivial time at the end when we've settled down) humans have been tribal hunter-gatherers. The forces at work in those societies would be very different than social forces in our present day society.

Krikket One: "Assume a average hetero has 2 kids on average but if they have a homo sibling they have 3 due to additional help hunting, etc.."

I think that this is a pretty big assumption. Each of this homosexual's siblings seems to become 50% more "productive" because of his presence, which doesn't seem to track with my conception of the problem. Why is this one sibling SO beneficial to his brothers and sisters?