Banning incest - natural reaction or stuffy old morals?

[PrinceAlarming]

But I do not understand how you can reconcile your idea with the large numbers of homosexuals who seek to have their own, biological children.

I think that the need to have a biological child is strong for all three sides of sexuality. There must be a biological need and/or want to spread your genes. But, in my experience, homosexual couples don't have "Irish twins" for a decade. For two men to have a biological child, one of them needs to provide the spermatazoa, and a surrogate mother must be found... That is much more involved than just rolling in the hay for 10 minutes. Overpopulation isn't caused by one couple having one or two children... It is caused by people having many children, and then their children having many children...

Wouldn't the population decline if all couples had only one child?

In anycase, I think I was just implying that homosexuality may be linked to overpopulation... What a homosexual couple seeks in terms of procreation may just be social pressure to make the relationship seem more "normal" or acceptable to their families... I don't know.

But back to the subject... What about homosexual incest?

[Primula Baggins]

PrinceAlarming, my gay friends with children certainly didn't want them "to seem more 'normal' or acceptable" to anyone. Their reasons were the same as most people's: the urge to form a family with someone you love.

The fact is that in many places even in this country, a gay couple with children is going to come in for more negative attention and criticism, not less. Many people believe that homosexuals are by definition unfit parents.

[PrinceAlarming]

It used to be considered the definition of unfit parenting for a child if they had both Catholic and Protestant parents... Black and while, rich and poor, Jewish and anything, Klingon and Romulan...

And yes, everyone has an urge to start mixing genes with someone they love... But a homosexual couple won't produce biological offspring unless that is what they want. As opposed to us 'breeders' who could have children due to a mistake in Las Vegas or a broken Trojan. A man who cheats on a man with a man isn't going to have an biological child. A man who cheats on a woman with seven women could potentially add seven more kids to the world (not including the ones he has at home already).

Homosexuality can still be a evolutionary response to overpopulation, even if gay couples want to produce biological children. It still wouldn't amount to what one striaght guy could do with his semineferous tubules and the sperm they produce.

This is all just speculation. Just an idea.

I'm sure we could discuss this issue further. It would be interesting. But that smells like another thread.

[Primula Baggins]

But, again, A can't produce B unless there is some kind of biological mechanism. We can say intellectually that a population with more gay couples is likely to produce fewer children, but what biological trigger would be switched "on" by overpopulation and cause more people to be born gay?

[nerdanel]

Just to be clear - I understand that in order for homosexuality to represent an "evolutionary response," it would have to have a biological basis, not an intellectual or conscious basis. But it seems to me that a biologically driven homosexuality would be of little use to nature unless it also came hardwired with a predisposition not to have children. (compare: biologically driven heterosexuality, which is of use to nature's procreative aims because it usually comes hardwired with a predisposition to have children.)

The point that I was trying to make - and I made it poorly, if at all - is that the two things do need to come together in order for homosexuality to be a worthwhile evolutionary response: both the biological hardwiring and the more conscious predisposition to act in accordance with the hardwiring. And gay people, broadly, do not seem particularly disposed to abstain from having children - whether based on conscious thought or on subconscious instinct. So if homosexuality is nature's foray into limiting overpopulation, nature has got some reworking to do.

What a homosexual couple seeks in terms of procreation may just be social pressure to make the relationship seem more "normal" or acceptable to their families... I don't know.

I doubt it. I've never encountered a same-sex couple who thought that procreation would help to normalize their relationship to their families or to the world, forget about a couple that has actually brought a child into the world for that reason. A lot of gay people really just want to have kids. It's stunningly ordinary and garden-variety, really...the exact same desire as a lot of heterosexuals.

As for your homosexual incest question: if both participants are over 18, it is absolutely their business. How adults receive their sexual gratification with each other behind closed doors is simply not our business - not yours, not mine, not the government's. Again, the ONLY reason I can see for the government to get into it is the potential (genetic) harm to children - which applies only to heterosexual incestuous couples who seek to procreate together. (As for children being reared in these hypothetical homosexual or heterosexual incestuous unions...I'm not sure. It seems strange to me...but at the same time, if the parents provide a loving, secure home, it seems as though there are far worse (and usually heterosexual, non-incestuous) family situations for the government to address: situations with family violence, drug use, sexual abuse, etc.)

[Crucifer]

- One of the reasons that I find homosexual sex strongly appealing is tha"the purpose of sex" is ipso facto not reproduction. It can only be an expression of the feelings (potentially, the love and commitment) between the participants.

But surely the act of love is in deciding to create a new life together, a life that you and your sexual partner will nurture and care for...

[Jnyusa]

For an increase in homosexual orientation to be a product of population pressure requires a mechanism, and it can't be an intellectual one; it has to be biological. And the effect must somehow be produced before birth, in the next generation.

The only comparable thing I can think of is the shutdown of menstruation and thus fertility in starving women. But that's a simple feedback mechanism.

Since we don't know what causes sexual preference, we can't begin to guess how the biological mechanism works. But there is no reason why it can't be a simple feedback mechanism. A host of physiological changes take place in all mammals in response to changes in population density.

In truth, I don't know whether the percentage of homosexuality is increasing in the population, because we don't have sufficient data. I made my statement based on deduction from characterisic mammalian behavior and not from sociological data. Mammals are inherently bisexual. That should give us a tiny clue where in the brain to start looking for sexual preference, if anyone is interested in looking.

To investigate the causes and mechanisms associated with sexual preference we would need much more than sociological data. We'd need data from homo habilis and before.

But I do not understand how you can reconcile your idea with the large numbers of homosexuals who seek to have their own, biological children. <> And gay people, broadly, do not seem particularly disposed to abstain from having children - whether based on conscious thought or on subconscious instinct.

nel, I'm not sure I am willing to accept at face value that the gay community as a whole is as anxious to procreate as you claim, though I don't dispute that it is true of the people whom you know. But even if this were true it would not be a challenge to the hypothesis, for the reason given by Prince A:

Overpopulation isn't caused by one couple having one or two children... It is caused by people having many children, and then their children having many children...

Natural selection acts on the individuals but influences the population via the law of large numbers. It is sufficient for there to be a gradient in reproduction rates for the mechanism to 'work' as it should.

Non-reproduction is the default position for homosexuals, and they must enjoin a third party to change that. This alone is sufficient to cause a gradient in reproduction rates. You have to remember that whatever the biology of homosexuality is, it's been there for ~40 million years, whereas the human sociology of it has only been around for ~70,000 years.

I read recently that the Hemophilia in the descendants of Queen Victoria was due to a rare but not unknown spontaneous mutation: it had not existed in that bloodline before. The article I read said it was not due to cousins marrying.

That's interesting, vison. I think you posted that once before somewhere - I had a deja vu when I read it! It is true, though, that you can trace the carriers of hemophilia through the European noble families and see how the incidence of two recessives influences the outcome.

Jn

[Primula Baggins]

Well, Crucifer, speaking as someone who is not gay and has been married for almost 27 years (with several children), procreation is usually a consideration for only a very brief time in the life of a couple, if it ever is at all. It's unrealistic to give it too much weight. Life would be rather grim if we all waited to have sex until we were ready to have our children, then stopped having sex as soon as we felt our families were complete. Most couples want more out of life than that.

[Crucifer]

Obviuosly, which is why the fact that sex is enjoyable is a bonus...

[Primula Baggins]

For an increase in homosexual orientation to be a product of population pressure requires a mechanism, and it can't be an intellectual one; it has to be biological. And the effect must somehow be produced before birth, in the next generation.

The only comparable thing I can think of is the shutdown of menstruation and thus fertility in starving women. But that's a simple feedback mechanism.

Since we don't know what causes sexual preference, we can't begin to guess how the biological mechanism works. But there is no reason why it can't be a simple feedback mechanism. A host of physiological changes take place in all mammals in response to changes in population density.

It could be, I suppose, although I have a hard time envisioning the kind of sustained selective pressure that would produce that effect over time in populations wiith long generation times.

And there's also the question of expression, as I mentioned earlier; for homosexuality to remove people from the breeding pool, they would have to be free to refuse to mate (something females probably never were in most of human history). And there has often been an advantage to having children that a homosexual male might still not forgo.

[Jnyusa]

... I have a hard time envisioning the kind of sustained selective pressure that would produce that effect over time in populations wiith long generation times.

Hm ... I'm not sure I follow this. We do evolve, in spite of our relatively long lifetimes ... For the top predator it's the supply line that matters, so it seems to me that all the selective pressures we've experienced must have taken that form. Anything that kept us midway between critical mass and carrying capacity would be favored in the long run. But I probably misunderstood what you meant.

Just speculating off the top of my head here, because I don't know anything about the biology of sexual preference, but it occurs to me that this might be like the question, "what good is half an eye?" The answer depends on what that half an eye was doing.

It might be that bisexual behavior was originally favored because it reduced intragroup conflict. In all mammals except humans, the females are only available when they're in heat, but selection would favor males that were johnny-on-the-spot whenever the female was ready (that is, synchronizing two cycles would be a relative disadvantage in species with low numbers of offspring), providing that what you did with the testosterone the rest of the time was to make love and not war.

Overpopulation might damp the reproductive urge in general via hormonal changes, i.e. non-human females don't come into heat when there is insufficient food, and then male homosexuality is the fallback position. We don't know the basis for sexual attraction really ... it could be that human females are also less attractive, for reasons not fully understood, when there is resource scarcity. And when the scarcity is severe, as you noted, women become unable to reproduce anyway.

Thing is ... any mechanism that operates primarily to remove males from the reproductive cycle is a weak inhibitor. It would be a lot more effective if female homosexuality were the primary effect ... but then, most of us would benefit from having three arms (I know I would!) and we haven't evolved one of those either. Or, it could be that female homosexuality did appear as a primary inhibitor at one time and it was too effective.

Sociologically, female infanticide is the common response to overpopulation. That's effective within one generation, without changing reproductive capacity in the generations beyond.

There was an interesting longitudinal study done at U. Penn on determinants of family size, but I don't have time to tell about it right now 'cos I have to get to school.

Jn

[Primula Baggins]

I'm not putting the idea clearly, Jn, but what I meant was, famines and such are usually short-term stimuli, lasting a year or a few years, so I don't see the selective advantage of a response that takes fifteen or twenty years to express itself. It's like pulling a fire alarm in May and having the sprinklers go off next year. By the time you got the result, the need might well be gone and the result might have become a negative.

I'm also suspicious of adaptations that result in less reproduction. Again, where's the selective pressure? If a lower population is the adaptive result, it can be achieved much more quickly by people dying of starvation than by taking individuals out of the reproductive pool.

As you say about the third arm, there has to be more to it than just "this outcome would be beneficial." There has to be a mechanism that can produce that outcome and do so in such a way that the organisms with the adaptation reproduce more. Not live longer, reproduce more. Mr. Prim has pointed out that he and I, both sterile now, are genetically dead. No adaptation that improves our lives now could be produced by selective pressure.

[Teremia]

Here's a wild-card factoid that links the "overpopulation" part of this discussion with the "homosexuality" part:

Study shows "each additional older brother increased the odds of homosexuality by 33%."

We could see that as a kind of feed-back loop, I suppose: a family with lots of (presumably fertile) heterosexual older brothers can "afford" (evolutionarily) a homosexual child. A large family would be a micro-instance and possible sign of "overpopulation" in the broader context.

[Jnyusa]

... famines and such are usually short-term stimuli, lasting a year or a few years, so I don't see the selective advantage of a response that takes fifteen or twenty years to express itself.

Ah. yes, I see what you mean. No, it could not be an isolated event like a famine unless the genotype somehow innoculated individuals against the event, and that would not be the case here.

I'm still thinking of this as a mammalian phenomenon, though, and not an exclusively human phenomenon, which means that population pressure does not come only from isolated events but from the long-term population size relative to the carrying capacity of its environment. Humans as such have not been up against the Malthusian condition, but nearly every other mammal has been.

I'm also suspicious of adaptations that result in less reproduction.

Yes, that's right. But keeping the population in between critical mass and carrying capacity actualy maximizes the growth rate. Where this comes out of kilter with evolutionary theory is that we usually presume that the adaptation belongs to an individual who perpetuates it by reproducing. Here we would be saying that this is a variable behavior potentially belonging to all individuals, and which disadvantages the individual in whom it manifests, but which nevertheless perpetuates itself by contributing to the growth rate of all who carry it.

I am talking about bisexuality, not strict homosexuality, because my understanding is that the latter is quite rare. (Did I say that already?)

Teremia, that article is really interesting! I think it does argue for the likelihood of a conflict-related biological source. But also might explain why the potentiality for homosexual behavior would persist even if the homosexual does not himself reproduce. The genetic rule is, you can afford to give your life for two brother or four first cousins, right?

Jn

[anthriel]

I think that the suppression of incestuous relationships based on the negative genetic pressure such pairings might perpetuate is something of a red herring.

"Line" or "In"-breeding can actually be a survival advantage, because it can intensify the effects of recessive genes. Obviously, not all recessive genes, if expressed, are a good thing. Nor, however, are they all bad.

There are many pockets of humanity which are "line"-bred, and are more closely related to each other than the general populations that many of us are familiar with. Much of this relative uniformity of genetic material was probably realized because of what we would consider "incestuous" relationships. However, because of this "line"- breeding, certain characteristics have been selected for by a combination of the matings of close relatives and a certain positive selective pressure.

For example, sickle cell anemia is common in people of African descent, and especially in people whose ancestors were located in areas where malaria was endemic. As it turns out, while the homozygous state of sickle cell anemia (called sickle cell "disease", it is a condition where the only hemoglobin produced is the much less efficient hemoglobin S) is generally eventually fatal, the heterozygous state (called sickle cell trait, where there is a mixed population of the normal hemoglobin A and the oddly shaped hemoglobin S) can change the rigidity and shape of the red cells just enough so that the malarial parasite can have a difficult time infecting them.

This group of people were interbred enough that the inheritance of sickle cell anemia was intensified, and there was enough selective pressure on that population to continue the ongoing inheritance of that genetic information.

Another example are the Pima Indians of Arizona. As Primula rightly points out, most famines are relatively short-lived, and will have no long-lasting effect on the genetic code, or at least which part of the genetic code is expressed. However, in the case of the Pima, they were alluvial farmers and also irrigation farmers, and relied on the continuing flow of the Salt River, as well as plentiful rainfall, here in the arid desert. Some seasons were very good, but quite frequently, there were seasons which were quite bad. Their cycle of feast or famine was greatly enhanced from the cycles of most other populations.

In this group of "line bred" people, the "thrifty gene" is very well expressed. The "thrifty gene" allows these people to store fat very efficiently, and is an amazing survival mechanism for the trying conditions of their ancestors.

However, that same gene is related to diabetes. Now that the environmental pressure of feast or famine has been relieved (along with the introduction into their lifestyle of the high sugar/high fat "Twinkie" factor, which I believe has had far more deleterious effects on their lifestyles than anything else the Europeans introduced), their "thrify" gene inheritance is actually a disadvantage.

If we were to regulate potential couplings based on their potentially negative genetic results, there would be far more problematic communities to focus on than those (few) who wish to mate incestuously.

I think the general aversion to this type of situation is cultural, and the handy justifications for those feelings are based in science. However, I am not sure that genetic science can fully support the absolute banning of such practices.