Ok, here’s the 2 part question:
Is homosexuality truly genetic in some cases? (In some cases such behavior must be caused by the environment, I would doubt that everybody who is gay is born that way and that environment can cause deviant behavior).
What is the evolutionary advantage? Why was it not selected out when it would seem that the genetic propensity to try and mate with the same sex would lessen the chances of a specimens genes being passed on to the next generation.
The answer to the first part of #1 is that we truly don’t yet know. A study done around 1991-1994 showed that when two brothers are both homosexual, the rates were something like 7% for independent birth brothers, 22% for fraternal twins, and 52% for identical twins. (Numbers are from memory and may be off several points.)
This suggests a potential genetic component, but there has been nothing like proof shown to date.
There are a couple of other correlations between physical features and homosexuality, but they are not clearly indicative (and the observations have been challenged), so I will not bring them in, here.
(You might want to limit your use of deviant in this context. Granted its denotation of “differing from the norm,” it still carries a lot of connotation that we would probably want to avoid in a general discussion.)
The speculation for question #2 is that a member of a group that does not engage in child-rearing contributes to the welfare of the group as a whole, meaning that some portion of his genetic thread will be passed on by his siblings. IF genetics plays a part in this scenario, then a periodic recessive trait that would provide additional support to continue the genes of the group makes sense.
There are a couple of species of birds in which only one male sibling of a clutch will mate and the others help provide food for that bird, his female mate, and their hatchlings. A similar event occurs among wolves, in which not every member of a pack mates, although all provide food for the pups.
None of this is conclusive, but it addresses the technical issues raised by your questions. (At which point, we might have been able to deal with this in General Questions, although, like religious questions, many questions on sexuality do tend to migrate to this Forum.
Should have been:
“does not engage in breeding, but does engage in child-rearing contributes”
Thanks tomndebb, especial for your response to #2. That is not something I have thought of before, the evolution of a advantage for the group as oppose to an individual.
It’s also possible that there is no evolutionary advantage to homosexuality itself, but the genes that contribute to it might also do other advantageous things. Or it could be that if you have 2 copies of gene Z you’re homosexual, but if you only have 1 copy of the gene, something evolutionarily beneficial could happen.
Or it could have no advantage at all, but survives because it’s recessive. Tay Sachs, for example, which almost inevitably results in its sufferers dying before adulthood, survives because the gene is carried in a large enough population and having one copy of the gene doesn’t cause it to manifest.
Is it possible that homosexuality occurs more frequently as overpopulation gets worse? Maybe a kind of shut-off valve for reproduction…?
Just throwing the idea out that…
But why would it mater if peple staved, as long as the genes got passed?
Not really. This is a good example of the teleological fallacy, the (invalid) assumption that evolution has a purpose/direction.
Until recently, lots of gays probably just pretended and even fathered children. One the ways human beings stuff up evolution is by not always following their instincts and drives.
Rigidly homosexual behavior (that is, only mating with the same sex) might not last too long among a population of animals. (or it might persist, because of other factors listed in this thread.) A gay dog will not pass on his genes. A gay human can, because of closeting or, these days, artificial insemination.
Indeed, I’ve heard frequently of lesbian couples having a gay man be the ‘sperm donor’ for their child, which might, if homosexuality is genetic, lead to homosexuality running in a family. Or not, it depends on how exactly homosexuality is encoded for men and women.
–John
Perhaps it is 2 genes acting together that don’t often actually come together but have a benefit on their own.
i.e. perhaps each act against catching a certain disease.
How many families of ‘all gay’ children are they ?
It may be that it is part of a ‘won’t mate anyway’ scenario i.e. too feminine male or butch female
I suspect that to be honest, in the past gay people still got married and had children as it was socially acceptable and now they can ‘out’ it will slowly die away.
I don’t think it will die out, as I posted just before you, a lot of gay families are having children by artificial insemination, so their kid has at least half the genes of the parent. And as time goes by, genetic engineering may improve to the point that two people of the same gender could combine their gametes to have a child that partakes of genetid heritage from both sides. (I can see problems here, obviously… lesbians would only have female children, for instance)
–John
Mutation certainly doesn’t have a direction, but wouldn’t you say that natural selection at least gives the impression of purpose or direction? If that were not the case, then it would be a lot harder for proponents of the intelligent design arguments to dupe their followers into believing in their brand of creationism…not that the impression of purpose provides any real evidence for intelligent external direction (special creation) at all, mind you. Dolphins have many adaptations that combine to make the animals extremely well-adapted to the aquatic life; while the mutations that got it to this point may have been random, the forces that selected for various adaptations were certainly directed by the environment and the challenges that environment produced.
Think about this; aging and death due to old age are apparently either selected for, or apparently the right kind of mutation to counter them has not come along. As the biological clock tocks down, it’s a completely normal and natural function, and it results in the death of the organism. Pretty negative, no? Yet it is beneficial to the population on the whole because it limits the strain on resources for the upcoming generations.
I know that naturalist E. O. Wilson puts forth the kin-selection theory of homosexuality.
Basically, a homosexual (let’s just say the homosexual gene is recessive) being does not procreate, but his heterosexual siblings do. He helps take care of his nieces and nephews, ensuring their survival, and the homosexual gene is passed along from generation to generation.
That’s kin selection in a nutshell. It might be a viable theory…I really don’t know.
Not known- I will say that the use of “genetic” to mean congenital is different from the use of “genetic” to mean heritable.
Individuals don’t evolve, populations do. Why should homosexuality have a survival advantage? It doesn’t matter what any individual or subgroup does, unless in the aggregate it lowers the population’s “fitness-” its reproductive advantage- below the level of that advantage.
We have to remember that our drive toward sex is just that: a drive toward sex. It is not a drive toward reproduction. As it happens, sex leads to reproduction, but evolution has developed a rather twisted path to get there. A more useful question is: what’s the evolutionary advantage of a sex drive over no sex drive? But then, why shouldn’t the sex drive have a spectrum of variations? If it were purely a drive to reproduce, it wouldn’t have variation, but it’s not. It’s just a drive to do fun things with our genitals (and other parts), with partners who feel and smell and look and sound and taste right to us individually. It works out that enough of the population will want to have sex with a partner with whom reproduction is possible, but WARNING- QUANTUM MECHANICS ANALOGY it also works out that when we fire a cannon at a wall, enough of the fields from the particles in the cannonball will be repelled by the fields from the particles in the wall for the cannonball to bounce off the wall, rather than pass through with no effect. This has no bearing on any individual particle, just as the “fitness” of bisexual reproduction has no bearing on individual members of a population.
I just had this great fantasy of Duane Gish saying: “Homosexuality proves Darwin was wrong. Gays are God’s Messengers!!!” Maybe I should apply to ICR for funding? JDM
I somehow doubt that said followers weigh out the scientific understanding of evolutionary principles before making their decision.
I think the problem is that your suggestion makes “nature” out to be a force with a will of its own that seeks to preserve itself. While its true that populations die off when they overpopulate an area, this isn’t because some “suicide gene” suddenly appears(lemmings are weird), or because anything changed at all. Instead, the same metabolic need for food and resources simply can’t be distributed widely enough. It’s not as though a mysterious force can say “its too crowded here, some of you guys need to be gay”
The death of the organism in one sense, but assuming that organisms had children, it’s no more dead than the prokaryote that just split in two (ie, genetic material still circulating). That said, the death of the individual results less from the triggering of some genetic population control device and more because of the degradation of material in our cells, which are specialized to the point where they don’t take care of themselves the same way a unicellular organism would.
Weird analogy, but picture two groups of people who all work together to build something. Members of the first group are constantly making sure their own bodies are in perfect working order and members of the second group just keep on working. Which group does the job better? So as long as the product is more important that the individual (communism anyone?), the second group will prosper.
One thing to keep in mind when reading that analogy is that I’m going by richard dawkin’s “selfish gene” theory of evolution: the gene is what needs to be kept “alive”, not the individual carrying it. So then you can see how the product of this aggregation of cells (reproduction and in the ideal case, multiple reproduction, leading to more copies of the gene) would be more important with respect to the gene than the body carrying that gene, so death by aging is fine.
In modern open countries with liberal gay laws how many people are gay and in the opposite cultures, how many get married and have kids ?
The previous poster is correct, they will not die out if they use insemination BUT how many gay men got married and had kids in the 50s and how many lived with another gay man ?
I am using non-statistical ‘gut’ on this, anyone got some data ?
Does it matter?
Esprix
Just because we can’t yet explain every force in the universe doesen’t mean they don’t exist. Some “mysterious” force says “hey there is food here, you should eat”. Likewise everyone could have a %3 chance of being gay and if the same impulse acts on 100 people 3 of them will be gay. The populations that overpopulate an area die off while the ones that don’t continue to live on.
Don’t wish to make this that kind of debate…
When cells don’t have material to much on, they don’t have the resources/engery to do what they’re supposed to do. When cells don’t do what they’re supposed to in a complicated system in which every cell depends on every other cell, that system doesn’t function properly. The same way pain functions as a way to say “don’t do that, we need that toe”, not eating results in a “we need food” situation. Obviously its not as active as all that, but hopefully it demystifies the “urge to eat”. THen of course there’s the more obvious urge when your stomach acid has nothing to digest so it starts to burn whatever it can find (hunger pains)… obviously we learn that eating avoids these pains.
All those statements are true, but what do they have to do with each other or the argument at hand?
Does it give that impression? Definitely. Does that mean things must be that way? No way.