If homosexuality is an inherited genetic trait, then it’s a bit too early for gays to be becoming extinct. Remember that homosexuality was repressed really until the 60s or 70s, maybe even the 80s and thus homosexuals tried to exhibit heterosexual behaviour. Some still feel suppressed. You need many generations - 100 years or more - for the gene (if it exists) to subside. To expect observable results within one human lifetime is not feasible.
I think I agree with you, but your examples confuse me. The ability to produce and respond to hormones is genetic. You posses genes encoding for enzymes that can convert cholesterol to steroid hormones, more genes that code for receptors of these steroids, and the receptor-steroid complex alter the expression of even more genes. I understand that, perhaps, a fetus does not have enough testosterone to drive brain differentiation towards the male pathway, but the underlying cause of that is likely to be the aberrant expression of one or more genes, with a small chance that the mother doesn’t consume enough cholesterol and the fetus is starved of steroid substrate.
The first part of that sentence is fact, but the second part is supposition. How many tried to exhibit heterosexual behavior? What type of heterosexual behavior? How many went so far as to marry and procreate?
That’s actually a good point. And let’s remember that it’s not like openly gay people don’t procreate, even if that might be at a lower rate than straights.
100 years would only be about 4 generations, and it’s impossible to say who quickly or slowly a gene or genes would disappear if it or they reduced the reproductive success of the person with the gene(s). And if there were recessive genes involved, they can lie dormant in the population for a long time before they meet another recessive match.
However, I would be very surprised if whatever genetic component there is consists of just one gene. And if it’s the mother’s hormonal balance during pregnancy that is the cause, then it’s her genes you need to focus on, not the genes of the gay people themselves. In the case of birth order correlation with homosexuality, it is thought that has to do with conditions in the womb, so women would still be passing the genes onto their daughters whether those daughters are gay or straight.
I’ve read a pretty fair amount regarding the twin studies related to homosexuality, and although roughly 50% is the given figure, I personally don’t accept that number for simple and basic reasons: (1) They all were based on self-reporting, and (2) there was much stronger social antagonism and pressure against identifying and reporting oneself as a homosexual. This would have a huge negative impact on self-reports of homosexuality, even if your twin brother was willing to go on record.
I’ve known three pairs of gay identical twin brothers and one set of gay identical triplets, and although a few of the brothers claimed not to be gay, in every case their twins privately said otherwise.
If the researchers had used some kind of objective measurement, hopefully something better than the “penile spygnomometer” kind of thing – say like a device that tracks eye movements while looking at photographs of men and women – I contend the concordance would be much higher. I tend to doubt it would reach 100%, though, so a discrepancy would still exist.
I’m a strong advocate of the kin-selection hypothesis of homosexuality to explain the continuing and large distribution of gay “genes” (the plural is important because at this stage I imagine we would have discovered the single gene in question by now). There are very probably multiple genetic “routes” to homosexuality, and I’ll bet their very different for men and women.
But because of the birth-order effect and important prenatal hormonal influences, it seem to me that the genetic contribution to homosexuality might lie not in the offspring’s genes but in the mother’s. If that’s so, we might be looking in the wrong place for any gay genes.
ETA: Oops, I see John Mace has suggested just that just previously. I remember our discussion, John, about precisely this issue. Perhaps I may have prompted you to start to think along those lines? Just a little bit?
As others have already pointed out, that’s where the kin-selection hypothesis comes in.
Think of the prehistoric Uncle Steve, when all of this was evolving. Since gay, un-partnered Uncle Steve has no mouths to feed other than his own (i.e., no children), but his straight, partnered sibling does, then if he were to help around the sibling’s cave, teach, and especially do things like contribute calories to his nieces and nephews (which is easier for him than for his partnered sibling), then the kids experience quite a substantial increase in their fitness. And since they share a large fraction of Uncle Steve’s genes, you’ve thereby managed to increase the presence of Steve’s genes in the population. Viola! No gay extinction.
I, personally feel the powerful presence of what may well be the kin-selection hypothesis working though me. I feel a powerful urge to lavish time and gifts on my nieces and nephews!
Because, at a very broad overview level, diversity provides an evolutionary advantage. Diversity translates into more flexibility, more ways to respond to changing conditions, thus more chance that one of the responses will be effective in coping with the changed environment.
It has been mentioned before, but a gene can be useful and deleterious depending on the situation, such as that for sickle cell anemia. It could well be that 1 gay gene = straight, but can cook, clean and looks after ones appearance = attractive to women = breeding success.
2 gay genes = homosexual
There have been some excellent posts here regarding reasons why homosexuality might persist in a population, even if though it likely reduces an individual’s reproductive rate compared to heterosexuals. One thing that is often ignored in these discussions, however, is whether homosexuality even occurs in the population at a high enough rate to demand some special evolutionary explanation.
The rate of homosexuality in the general population is often given as about 10% or even higher, but the actual percentage of exclusive homosexuals – those who never or almost never have sex with members of the opposite sex – is almost certainly substantially lower. I have seen figures of about 2-5% for males and about half that for females.*
The rate of sterility due to purely physiological factors is probably 1% or greater.* Beyond that, a substantial percentage of heterosexuals remain childless throughout their lives for various behavioral reasons, including extreme shyness, social ineptness, religious celibacy, or other factors. Then there are others who are simply asexual, and have little desire to mate with either sex. Some of these behaviors could be just as heritable as homosexuality. These groups together almost certainly comprise a larger percentage of the population than exclusive homosexuals.
Yet it is rare for anyone to suggest that an evolutionary explanation is needed for these kinds of behaviors. They are recognized as being due to some kind of miscue of genetics, development, or socialization, or in some cases, such as religious celibacy, even seen in a positive light.
While it is interesting to speculate on why homosexuality persists in populations despite a negative effect on reproduction, in my opinion an evolutionary explanation is unnecessary. There are many other behaviors that have an equally detrimental effect on reproductive success, and that probably occur at a greater rate than homosexuality, that are most likely maintained in the population simply by non-selective factors.
- No cites for these figures here, but I have looked them up for other threads on this subject, and they are in this ballpark.
Yep, those are the numbers I’ve usually seen, too. I believe the 10% number is a holdover from the Kinsey studies. Those studies, as revolutionary and informative as they were, are often recognized as being flawed. This type of data is very difficult to collect, however, and Kinsey’s introduction of the spectrum of attraction is perhaps the better way to look at things.
If we were to ask what percentage of the population is prone to any type of behavior, we’d almost certainly find that we would have to draw an arbitrary line somewhere if we wanted to categorize everyone into only 1 of 2 boxes.
I agree. Witness the Molly Clubs of 18th century London.
For what it’s worth, among my rather tight circle of friends, more of the gay men & women have had kids than the straight ones.
Not much of a sample size, and unscientific, but I’d say gays & lesbians are holding their own in the baby-making dept.
Well, I think it’s correct to say that it’s a modern concept in the sense of it being something intrinsic to the person, and not something that can be changed. Remember, it was only in the late 1960s (or was it early 1970s) that psychiatrists stopped classifying it as some sort of mental disorder, possibly related to how a person was brought up. The idea that someone could be born homosexual wouldn’t have carried much currency until recently, even if a few enlightened folks might have accepted it. Or perhaps some gay people in the past may have intuited that they were born that way, although I suspect they would have been told otherwise by whatever authority they consulted.
That speaks only to western culture, btw, and there may very well have been other cultures that someone accepted the idea that person might be born one way or the other, or that they might be a “two souls” person, like the *Winkte *in Lakota society.
Let’s also not forget about intersexed people, and the confusion they introduce into this subject if we try to figure out which sex they “should” be attracted to. Further to idea **Coibri **brought up earlier, why do people focus on some sort evolutionary need to explain homosexuality, but so rarely when it comes to something like intersexed people? Frankly, that speaks to either a misunderstanding about what evolution and how it works, or some need to justify homosexuality and prove that it is beneficial to society. It may well be beneficial (directly or indirectly), but it needn’t be just because it persists.
And if the genetic component* is from more than one gene, certain combinations of those genes might lead to more reproductive success, even if other combinations lead to less. In that case, a few homosexuals who reproduce less are a small price to pay, in evolutionary terms, for the greater reproductive success of some people get from being only “part gay” (ie, not having the combination that leads to homosexuality).
*assuming there is one
I think people are ignoring my former post which may well not be the whole story but it is still crucial. Genetics don’t directly determine sexual preference or even phenotypical sex (whether you look like a male or a female). That is the domain of the sex hormones and genetics (XY, XX) only help kick off this process but don’t determine it directly. Having a genetic sex that doesn’t match what someone appears to be isn’t really rare and you have met some people who appear female but aren’t genetically because of a flaw in this process.
Brain sex is determined through critical periods that look for presence or absence of sex hormones before deciding to become male or female and not all critical periods have to match in one organism including humans.
The way this thread is going tends to be like similar ones and pisses me off because people are not male or female directly because of genetics. The sex hormones do that and although genetics help kick off the process, they are not the primary determinate. It is very easy to induce mismatched sexual characteristics in animals through hormone injections as has been since the 70’s.
Again, genes don’t directly determine if an animal or human develops a certain brain sex or body sex. It is the sex hormones and that can easily explain why identical twins can have one as heterosexual and another as homosexual. The research on all of this is incredibly robust and goes back to the 1970’s yet, every time I see people discussing it in writing, people tend to completely ignore this research and the fact that phenotypical sex as well as brain sex aren’t directly controlled by genetics. It is bizarre to me.
!!!Genetics don’t directly determine either brain or body sex. It is stupid to move past the primary level (sex hormones and development) and try to dive down into genes without understanding how the primary level works and how it could explain everything (quite well).
I think the distinction between directly affecting something and indirectly affecting something is not a very useful one to make in this instance. We are talking about evolution here and if you don’t talk about genes, it’s hard to talk about evolution. But ultimately, sexual attraction has to have a genetic basis, or it wouldn’t exist in the first place.
But that is the whole point. Disorders affecting hormonal critical periods don’t have to be linked to genetics at all anymore than breech births do. It is just an accident like many things that can happen during development that don’t have a genetic basis. It may be possible for a genetic line to be susceptible to these kinds of anomalies but that still doesn’t make it a genetic issue. The sex hormones are still in the driver’s seat when it comes to the sexual differentiation of the body and brain and countless experiments and scientific theory make it clear that genes to need to be included at all if the process goes awry at any point in the differentiation process.
Why on earth would universal procreation and parenthood be a good thing? We already live in an overpopulated world, and there are ***many, many ***people who neither want kids nor are qualified to raise them, including many who nevertheless do. For too many people parenthood is not a positive experience, neither for them nor their kids.
On those grounds, it would actually be best for everyone to be bisexual, and having the choice of which gender to like on top of that. Not only both procreation and parenthood, but also the freedom to have a relationship with anyone.
Also i’d probably say they had easier potential, rather than actually experience. Heterosexuals aren’t guaranteed procreation/parenthood, though of course it’s easier for them.
Correct me if I’m wrong, but aren’t scientists actively engaged in trying to find the cause of homosexuality, including looking at genetics?