Darwinian Evolution Question on Homosexuality?

Question

I buy Darwin and his evolutionary theories 100 %. One thing that puzzles me is how do genes for homosexuality get passed on, since presumably homos engage primarily in non reproductive sex. What selective pressure could their be to make this non reproductive behavior persist and how is it passed on? Of course, Im assuming that in many cases, genes play a part in a persons being gay or straight.

Answer 1

What I find fascinating about all the answers above is that most of them don't even make the other assumption that "gay" behavior might well be selected for in an evolutionary context and be something that confers a selective advantage to the family line.

It could be selected for as an adjuct to something else or because having homosexual behavior and/or homosexuals in a band might well actually INCREASE the number of offspring left by their relatives. Does this necessarily have to be because the homosexual individual leaves his/her own offspring? No. It could be that there is near-kin selection. After all, think about this - let's just assume we're talking about males here, because females of whatever sexual persuasion could be bred by more aggressive males in a hunter/gatherer society. Assume that three or four males are homosexual in a moderately small group and that they are related to the others there -- gosh, what a concept, huh? These men bring in more food, share with the tribe (relatives) and help survival of all in the group, and yet they basically don't infringe on the mating perogatives of the breeding males. There are also more males available for defense of the band. It won't cut down on the breeding numbers either, since again, all females will likely be pregnant anyway. The males aren't having fights among themselves and you have a possibly more stable situation than if you had non-breeding males who were seeking females. (Is this what happened? I don't know, but I can easily see an evolutionary context for it. Heck, Greylag Geese that have homosexual triads rear way more young-- a triad is a male bonded pair that also includes a female. ) What makes you think that such couplings aren't known in human populations too - and may well have been at least as common in the past as they are now? Since the non-breeding males (homosexual ones) help the tribe produce more young - and since the young are related to them, the frequency of genes that allow the behavior can spread in the population.

Answer 2

Homosexuality may be genetic but probably at the level of selective gene expression. There have been studies that suggest that the mothers body become resistant to testosterone after the first born male so in some cases it is the second born male that has homosexual tendancies. psychologists will say that it starts out genetically like the inability to sweat when engaging in physical activity that leads to a predisposition to staying in doors and associating with females thereby viewing the male sex as errotic. It's all nature vs nurture.

Answer 3

Lately some research is focusing on the impact of the conditions of fetal development in the homosexuality. It seems it has a lot to do with the amount of male/female hormones one was exposed to while still in their mother's womb. A study even suggests that the more older brothers a guy has, the more he is likely to be homosexual. This is because the mother's body tends to "see" the baby boys body as a foreign thing, and so tries to "feminize" it by pumping into it more female hormones. If that mother keeps having baby boys, her body becomes an "expert" in "hormone bombing", and so every new baby boy has a bigger chance of being homosexual than its older brother(s).

I read this somewhere, and I found it quite interesting, altough it doesn't explain female homosexuality. For a very long time people thought that homosexuality was all about the upbringing of the child. Then, with the boom in molecular biology and genetics, a lot of people started focusing on finding the "gay gene". Now it seems they are leaning towards investigating what happens during embryo development, since those 9 months have a far bigger impact in our personality and health conditions than we could have ever suspected. If this is the case of homosexuality, Darwin has nothing to do with it ;-)

PS - Homosexual behaviour is seen in a large number of animal species, including primates. In this case, it seems to be a social skill that allows to keep the peace in exchange for sex, so it can be quite useful in terms of survival ;-)

Answer 4

I read a research paper one time (recent past) that said if a man has a family of only sons, at least one of the sons will be gay. This is based on the supposition of supply and demand in relation to the human population. The paper went on to suggest that homosexuality is necessary to control population over crowding. In looking around, I have a hard time believing that angle. I thought it was an interesting argument, however, and can see some validity in the theory. Do I believe it to be gospel? No. Great question Jeff! Nana

Answer 5

There are many conditions which are not conducive to reproduction of offspring, such as Sickle cell disease and Cystic Fibrosis. But in their carrier states confer a selective advantage to the group/ village/ family as a whole. Perhaps homosexuality, although obviously not a disease, in some way contributes to society in this way. It certainly has been maintained in the gene pool, as you rightly point out. As to whether it is a genetic trait or not is still being debated, but it certainly acts like one. Perhaps, like Sickle Cell anaemia and Cystic Fibrosis, it is the homozygous form of a beneficial condition.

Just my thoughts.

Answer 6

There is no gay gene. And the problem in your question is that you're talking about Human like they were Animals: Human is probably the only species on Earth that doesn't follow Darwin's theory of Evolution.

There are a lot of genes that are transmitted and that make people die: myopathic diseases for example. The people who are born with these conditions don't survive until they get children but the genes subside anyway.
Thing is, homosexuality is not a disease, it is a personality trait who many people would like to put a gene on.

Answer 7

Read raquel's answer ... it is excellent.

There are many explanations that can explain the existence of homosexuality in many species (not just humans) ... and all of them are fully compatible with Darwinian evolution ... and the correct answer may be a combination of *all* of them (as they are not exclusive).

First, in a social species, survival often means survival of the *troop* as much as (or even more than) the *individual*. In other words, variation within a troop, where many members have different behaviors and roles, makes for an effectively surviving *group*. If all male genes produced alpha hetero males, the troop doesn't last very long ... and as a consequence, neither do those genes. Humans are an *extremely* social species ... and development of language, and thus of human intelligence itself, seems to be tied to social behavior ... and thus the frequency of homosexuality may be a side-consequence of the same social relationships that led to intelligence.

A second explanation is that a behavior can still be "innate" even if it's not genetic. As raquel explains nicely, many characteristics can be determined very early in childhood, or even by hormonal environment in the womb, even if there is nothing in the genetics of the baby itself. Even identical twins can have differrent hormonal environments (prenatal endochrinology is complex) or different formative experiences in very early childhood ... although twin boys are more likely to have the same sexual orientation, this is not always the case.

But the point is that sexual orientation, even if there is no 'gay gene', can still be quite fixed by the time a baby is born, or by the time a child is 5 or 6 years old, and even moreso by the time the child reaches puberty ... so forcing a person to change sexual orientation as an adult is as difficult as asking them to change their fingerprints (which are also determined prenatally, not by genetics).

Third, there are many reasons why a "gay gene" *would* exist, that do not violate Darwinian evolution. Under sources I've includes a link to a discussion of the 'gay gene' by Richard Dawkins, and he mentions a few of these. E.g. a gene produces advantages (to the troop) when it occurs in some (but not all) females, and produce homosexuality when it occurs in some (but not all) males ... and thus there is good reason the gene will just propagate indefinitely in some (but not all) individuals, regardless of gender. There is also the 'sterile worker' hypothesis, and the 'sneaky male' hypothesis (see my source ... it's really interesting).

And finally, it's important to remember that *variation* is not only an *ESSENTIAL* ingredient of natural selection (it could not occur without it) ... but variation is itself a complex thing. For example, a minority of humans are left-handed, and this seems to be genetic ... but it is a myth to imagine that all humans are *either* strictly left-handed or right-handed. Most of us are somewhere in some range in between ... some are quite ambidextrous ... competent with both hands ... while other people (like me) are completely useless with our left (or our right). Sexual orientation seems to work the same way ... there is natural variation in sexual orientation, most people are somewhere in between, while some tend strongly to either one of the poles.

[Unscientific aside: homophobia, it seems, often appears in men who turn out to be slightly or strongly inclined towards homosexuality ... it appears to be a defense mechanism against their own homosexual urges, to be *extra* hostile to it, while *strongly* heterosexual men feel that homosexuals pose *less* of a threat, not more ... less competition. I say this is unscientific, because the evidence for this is anecdotal (since few homophobic men will admit to having latent homosexual urges) ... but as a straight guy, I'm always happy to have less competition for the ladies ... and every time it's the most homophobic, gay-bashing preacher or politician getting caught in a men's room or chasing young male pages, I am reminded of this.]

But the bottom line is that that there are a number of mechanisms ... all fully compatible with Darwinian evolution, by which sexual orientation of all kinds *does* seem to be established by the time a child is 5 or 6 ... and even more strongly by puberty.

Asking a person to change this sexual orientation is about as fair and realistic as trying to change their eye color or fingerprints ... or saying that left-handed people are obviously immoral and "unnatural" because they are a minority, and should simply "choose" the moral path of being right-handed like the rest of us.

[P.S. ... please stop using words like 'homos'. Treat people with respect.]

Answer 8

It could be that either homosexuality is a muitation-just like color-blindness,is in some way a recesive gene,or is caused by hormonal imbalances that occure durring pregnancy.

Answer 9

this is going to insult some human beings i'm useful, yet for my section, homosexuality is obviously a psychological illness. don't get me incorrect, i'm no longer homophobic, Im fairly especially liberal approximately it, I beleive comparable intercourse marriage could be allowed, and prejudice in direction of gay adult males and ladies shouldnt be universal. in spite of if because you advance darwin and evolution, in case you think of roughly it, there is not any way that being gay would be genetic or inherited. It does not determine survival of the fittest, and this is no longer in any way useful to a species. each and every organism from an evolutionary viewpoint is created with a view to procreate and subsequently be sure the continuance of the species. If someone is gay, then they gained't reproduce and could be weeded out by survival of the fittest, in spite of in the event that they for sure are not. in case you evaluate being gay to melancholy or schizophrenia you will discover the similarities. those psychological themes will certainly shrink the probabilities that someone will procreate, in spite of if this doesnt supply up extra persons from turning out to be depressed or schizophrenic in spite of if the trait isnt surpassed on. human beings will advance animals yet in reality human beings are the only species which will "elect" to be strictly gay, and could abstain from intercourse with participants of the different intercourse. (I say elect for loss of extra suitable terminology, after all noone chooses to be depressed or have any psychological illness. this is why that's a illness) Male dogs will hump different male dogs, yet once you place a woman dogs into the mixture, that comparable dogs will attempt to reproduce with the female to, human beings arent so elementary. Our brains artwork like super complicated computers, and it doesnt take plenty to alter the way the recommendations works, annoying experiances, loss of love, or maybe previous psychological ailment are all issues which could impression the recommendations and reason someone to advance into gay. we don't comprehend how the recommendations works that's a long thank you to complicated, each and every from time to time someone with a likely applicable existence will turn gay. yet those comparable those with applicable lives are additionally liable to suicide melancholy or any psychological ailment. to respond to your question, confident. in case you think approximately homosexuality as a psychological illness than they do coexist.

Answer 10

To the above - Yes .. it does contribute to society as a whole. We will all eventually be well dressed and have fabulous window treatments!