If a mother rat engages in behaviors like eating her offspring as a result of overcrowded conditions, she’s improving the chance that her other offspring will survive, and thus pass her baby-eating genes on further.
I don’t see why being gay would work that way at all. Say a little baby rat has the gene that causes him to go gay if his cage is too crowded. He grows up. His cage is too crowded. Whoops, he’s gay. He doesn’t pass his genes on. Poof! So much for those gay genes. Since his hetero brothers and sisters (ones who lacked the gene) are still more likely to survive and reproduce - even considering the diminished likelihood within the overcrowded environment - their genes are the ones that will be propogated.
The popularity of this idea, that overcrowded conditions lead to homosexuality, is just a sign of how poor most people’s understanding of evolution is. Evolution is not a magical force that creates organisms perfectly suited to their environments. All evolution is is selection by the environment that causes some genes to be passed on and others not to. It’s certainly the case that some genes that limit reproductive ability get passed on - menopause is often cited as a phenomenon mostly limited to humans that seems counterintuitive from that perspective. But since the function of menopause - as with the function of baby-eating - is to ensure that the mother’s other children survive and thus that her menopause genes get passed on, it makes perfect sense. Genes that turn a person gay in response to their environment wouldn’t be very likely to get passed on, since gay people are less likely to have children.
If a reasonable evolutionary mechanism that accounts for homosexuality is discovered, rest assured it will be much more complicated than this one.
There are bacteria films that have a propensity to “commit suicide” when faced with adversarial environmental conditions, ostensibly to make it easier for their brethren to live on. I don’t see why it’s impossible that humans have a similar setup, especially since the human individuals would not commit suicide but rather still be able to help transmit their relatives’ genes.
Now, when the negative environmental conditions continue, it is true that the bacteria that survive are much less likely to autoapoptose due to selective pressure as you mentioned (even though it returns quickly if the pressure is let off.) I suspect that if crowded conditions genetically encourage homosexuality and if the pressure continues, in several hundred to a thousand years we will see a reduced homosexuality, especially if it continues to cease to confer sociobiological genetic advantage due to the continuity of the nuclear family as the most important social unit. But any such change would take lots of time, especially as whatever genes that might lead to homosexuality do not appear to be triggered anything close to %100 of the time.
It would if it would increase the survival of the gay people’s siblings. The Selfish Gene is all about this. Sometimes other members of the population sacrifice themselves, intentionally or not, in order to help their siblings survive. Nature does this in a wide variety of ways. I do not believe stress is the only factor that contributes to homosexuality - it seems to be polygenetic. But it’s perfectly good evolutionary theory.
No, the “overcrowded” thing doesn’t deal with genes at all. It’s an environmental theory. As you know, our bodies produce different hormones based on the environment we’re in. For example, when we’re scared, we produce more adrenaline, which sets up a “fight or flight” response.
So, lets say that when a rat is overcrowded or stressed out, it produces more of a certain hormone as a response to that stress…let’s call it “Hormone X”. So, a stressed rat has more of Hormone X in her body than an unstressed rat. Now, lets say that rat is pregnant. Because momma rat is pregnant, she’s sharing her blood, and everything in it, with the little fetal rats…that’s how they get the nutrients they need to grow and develop. That means, though, she’s not just sharing oxygen and nutrients with tbe little fetal rats…she’s also sharing Hormone X with them.
Now the little fetal rats are developing, which means that, among other things, their brains are developing. So, it’s possible, say the people that subscribe to the theory, that, if the fetal rat is exposed to a certain elevated level of Hormone X at a certain time in its development, its brain will develop differently than if it were exposed to normal levels, and if this part of the brain that’s affected is the part that determines sexual desire, then you’ll have a “gay rat”…one that’s sexually attracted to its own sex.
Either the siblings share the genetic predisposition to become gay - in which they’re also likely to sacrifice reproduction - or else they don’t. In the first case, it’s hard to see how the gay gene ends up being perpetuated, since the only time it’s being actively selected, it’s likely being selected against. In the second case, it makes a bit more sense - except that the gay genes then inevitably end up pulled out of the market.
They wouldn’t be removed if the trait was advantageous when it is heterozygous. Sickle cell anema is perpetuated genetically because it confers an advantage to those with the heterozygous genotype. They are able to contact malaria without getting sick and dying. These individuals have a risk of giving birth to babies that will die, but they also give birth to individuals that have a greater chance of survival.
Mom x has a mutation which causes her to give birth to babies with a same sex attraction during times of stress. IIRC, homosexuality has an incident rate of 50% in indentical twins which suggests that it is polygenetic, which means that not all kids are equally effected by it. Not all of mom x’s kids reproduce, but a higher percentage of them do and those that do carry the gene. Since it is polygenetic, it isn’t always turned on. All of the kids may have the ability to turn gay if the right factors are in place, but because so many factors are involved, only a few actually do.
Mom y does not have the mutation. She gives to kids who give birth to many more kids and the population grows out of control and all her grandchildren die off.
Of course, homosexuality is caused by many more things than just prenatal stress. But I think it would be bad science to dismiss this theory as not contributing anything to the biological cause of homosexuality.
Only if it doesn’t actually weed itself out of the gene pool on first appearance; elements of the population that respond to overcrowding by dying out aren’t going to pass this useful ability on. I realise that’s a bit of a simplistic view though.
Oooooh, that reminds me of something. There are theories that homosexuality is caused by relative overcrowding. There are other theories that homosexuality is a side effect of an otherwise genetically pro-reproductive trait (such as the sickle cell example.)
Why can’t it be both (like the late Earl Warren? :D) The same genes that provide an increased chance of homosexuality might give an evolutionary advantage totally separate from sexual orientation, and might cause an increased rate of homosexuality only during stress/overcrowding.
Not nessesarily.It seems that in some species a brother male stays single sometimes in areas of high stress, and becomes an “uncle” and hels insure his brothers offspring make it. Thus, he helps pass on part of his genetic make-up. This isn’t well understood mind you. More or less what **kimera **has said.
BWAHAHAHAHAHA! Obviously this guy has never been to a monastery,
or a rectory,
or a seminary.
Truthfully, there is a pretty good reason for large gay populations in port cities. During and after WWII, there was a significant increase in the gay population of most major port cities. Most gay men and women in the military who were discharged for homosexual activity did not go home. They stayed where they were discharged, and made a life for themselves there. Dishonorary discharges did not go over well in small town America.
Huh. I originally opened this thread expecting something about mechanisms for normalizing sex ratios in a population. Maybe a little bit on kin selection, things like that.
Instead, it’s some guy conflating homosexuality and AIDS.