Is the existence of homosexuality incompatible with evolution?

wellwisher said:
Darwin has the males competing for reproductive rights.
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No, he doesn't.

His theory explains it, when it occurs. It also explains the large fraction of species in which it does not occur, the large variety of ways other than contributing to direct competition between males in which a gene can gain selective advantage over another gene, and so forh.
 
Rhaedas said:
So people who preferred a gay life but due to societal prejudices took on a 'normal' hetero family role for many years, when they finally came out, they were lying? Your claim assumes that a person is sure of their preferences from the start AND can pursue them without any backlash. Which isn't true at all.
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No..self-identified gay people do not have heterosexual sex. That's why they call themselves "gay". Could there be alot of bi people confused about what they want or perhaps homosexuals who drifted into the whole "get married and have kids" program of their society and repressed their innate desires. Sure, but I wouldn't call these people "gay". I'd call them "confused".
 
Magical Realist said:
The Biological Basis of Homosexuality
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"A biological basis for human homosexuality is well established in the scientific community, but the exact mechanisms are unknown. It is believed to be a combination of genetic and hormonal factors.
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It seems to be a cause of both environmental and genetic inheritance.
 
Hercules Rockefeller said:
I just don’t get this rationale. It crops up semi-regularly and there is no need to invoke convoluted caretaker hypotheses to dismiss it (although such hypotheses may have merit). The premise that homosexuality is incompatible with the ToE because homosexuals do not produce offspring is demonstrably wrong because clearly homosexual people do procreate. Many homosexual people remain ‘in the closet’ while they pursue traditional marriage and have children. Additionally, many homosexual females utilise sperm donation to produce offspring.
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Homosexuality also may be due to some common error that occurs during reproduction like Down's syndrome which clearly offers no reproductive advantage (the males are usually infertile) yet persists in the population because the same error keeps popping up.
 
madanthonywayne said:
Homosexuality also may be due to some common error that occurs during reproduction like Down's syndrome which clearly offers no reproductive advantage (the males are usually infertile) yet persists in the population because the same error keeps popping up.
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Genetic mutations like Down's Syndrome are easily traceable to a chromosomal abnormality, particularly the duplication of an extra chromosome. If homosexuality were a genetic mutation it would be similarly traceable. It isn't. And the base rate of it's occurrence is way to high to attribute to random errors. It's definitely part of our normal DNA--like having blue eyes or being left-handed.
 
I just want to say I have no problems with gay people and I dont want my words misconstrued, I am only speaking from an evolutionary biology perspective.

Originally posted by Magical Realist
the survival of a population has more value than the survival of an individual animal
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Natural selection acts on the level of alleles, genes and individuals, not populations in most cases. "altruism" helps the individual reproduce, where it is observed, but It shouldnt be mistaken for some idea of the greater good. The unusual example of Hympenoptera et al., such as ants relates to an unusual scenario
of relatedness, as well as other complexities, and doesnt apply to humans.

A major issue here imo is not to view homosexuals and heterosexuals as separate forces in the evolutionary process. Its about the gene and/or genes involved. As pointed out earlier in the thread, heterosexuals clearly produce homosexual offspring. One potential explanation is spandrels, as someone has already proposed as side effects genes earlier in the thread.

spandrels, originally conceived by Gould and defined as in evolutionary biology to mean any biological feature of an organism that arises as a necessary side consequence of other features, which is not directly selected for by natural selection. So, certain human behaviour do not increase chances of survival, gain, and or reproduction, they are a result of a spandrel, whereby this behaviour exists due to biological constraints and was selected for in the first instance as it accompanied other advantages which has allowed us to survive, reproduce and flourish as a species, but more relevantly at the level of the individual (or in true terms at the level of the allelle).

A possible explanation? Its an interesting debate.
 
Magical Realist said:
No..self-identified gay people do not have heterosexual sex. That's why they call themselves "gay". Could there be alot of bi people confused about what they want or perhaps homosexuals who drifted into the whole "get married and have kids" program of their society and repressed their innate desires. Sure, but I wouldn't call these people "gay". I'd call them "confused".
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Well, you could also call gay people "confused" because normal people have sex with the other sex. But that's sort of a silly definition.

There are people who have sex with only the opposite sex, and people who only have sex with people of the same sex. There are people who have sex with both. There are people who do one of the above three for a while, then do another. It doesn't mean any of them are confused. They may be doing exactly what they want to do, for reasons that are important to them.
 
tantalus said:
I just want to say I have no problems with gay people and I dont want my words misconstrued, I am only speaking from an evolutionary biology perspective.


Natural selection acts on the level of alleles, genes and individuals, not populations in most cases. "altruism" helps the individual reproduce, where it is observed, but It shouldnt be mistaken for some idea of the greater good. The unusual example of Hympenoptera et al., such as ants relates to an unusual scenario
of relatedness, as well as other complexities, and doesnt apply to humans.

A major issue here imo is not to view homosexuals and heterosexuals as separate forces in the evolutionary process. Its about the gene and/or genes involved. As pointed out earlier in the thread, heterosexuals clearly produce homosexual offspring. One potential explanation is spandrels, as someone has already proposed as side effects genes earlier in the thread.

spandrels, originally conceived by Gould and defined as in evolutionary biology to mean any biological feature of an organism that arises as a necessary side consequence of other features, which is not directly selected for by natural selection. So, certain human behaviour do not increase chances of survival, gain, and or reproduction, they are a result of a spandrel, whereby this behaviour exists due to biological constraints and was selected for in the first instance as it accompanied other advantages which has allowed us to survive, reproduce and flourish as a species, but more relevantly at the level of the individual (or in true terms at the level of the allelle).

A possible explanation? Its an interesting debate.
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So which is it? The gene complex causing homosexuality IS advantageous for survival? Or it isn't? I think the idea that the gene complex could contribute to the fertility of heterosexual siblings has been mentioned several times. Is that what you are proposing? I find that a sound argument.
 
billvon said:
Well, you could also call gay people "confused" because normal people have sex with the other sex. But that's sort of a silly definition.

There are people who have sex with only the opposite sex, and people who only have sex with people of the same sex. There are people who have sex with both. There are people who do one of the above three for a while, then do another. It doesn't mean any of them are confused. They may be doing exactly what they want to do, for reasons that are important to them.
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A gay person who has sex with and is attracted to the same sex wouldn't be any more confused in their orientation than a straight person is. They know exactly what they want and get it. A person who practices one kind of sex while preferring another instead otoh? That would be my definition of "confused."
 
Is that what you are proposing?
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no, I am proposing that homosexuality is tied to other traits at the genetic level, that enhance survival and/or reproduction, and that the gains of such outweigh the accompanying homosexuality genes (which offers no benefit) in terms of the survival of the fittest. That homosexuality is a spandrel.

For example it has been worth while for humans to evolve big brains and intelligence despite the fact that it leads to complex disorders and actions such as suicide. edit. This is not meant to be a comparison, just an example of how a spandrel could arise.

think the idea that the gene complex could contribute to the fertility of heterosexual siblings ..... I find that a sound argument
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that also sounds plausible, I just offering another potential explantion
 
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tantalus said:
no, I am proposing that homosexuality is tied to other traits at the genetic level, that enhance survival and/or reproduction, and that the gains of such outweigh the accompanying homosexuality genes (which offers no benefit) in terms of the survival of the fittest. That homosexuality is a spandrel.

For example it has been worth while for humans to evolve big brains and intelligence despite the fact that it leads to complex disorders and actions such as suicide.
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So what would these other traits be that outweigh this hypothetical deficit for survival that homosexuality would cause?
 
So what would these other traits be that outweigh this hypothetical deficit for survival that homosexuality would cause?
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I have no idea, but the question is is it a credible theory? The traits could be entirely unrelated to sexuality I imagine (purely speculation on my part), it relates to biological constraints that we have little notion of as of yet. Spandrels are now a readily accepted phenomenon, proving a spandrel is a spandrel is an entirely different matter. Tradeoffs at a genetic level are however a clear reality in evolution.
 
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tantalus said:
I have no idea, but the question is is it a credible theory? The traits could be entirely unrelated to sexuality I imagine (purely speculation on my part), it relates to biological constraints that we have little notion of as of yet. Spandrels are now a readily accepted phenomenon, proving a spandrel is a spandrel is an entirely different matter. Tradeoffs at a genetic level are however a clear reality in evolution.
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So you're saying someone born gay may have special traits that make them so superior in survival that it counteracts their disadvantage in breeding? What could that be? Intelligence? But even with intelligence, if you're not breeding you're not going to pass that trait on. This is the problem in limiting survival advantage to the individual. There doesn't seem to be ANY trait that could counteract the disadvantage of not breeding. OTOH, on the family and tribe level such traits COULD make having the gay gene complex advantagous, as the article made clear.
 
So you're saying someone born gay may have special traits that make them so superior in survival that it counteracts their disadvantage in breeding
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no what I am saying is that the process results in heterosexual individuals retaining homosexual genes over evolutionary time, which they pass onto some of their offspring and that this disadvantage of producing offspring that will not pass on their genes (as they are gay) is due to some other related and tied beneficial traits which outweigh such a negative (in Lifetime reproductive success).The focus is not on why gay people continue in the evolutionary process as a distinct entity but why heterosexuals retain the gene over evolutionary time
 
Magical Realist said:
So you're saying someone born gay may have special traits that make them so superior in survival that it counteracts their disadvantage in breeding? What could that be? Intelligence? But even with intelligence, if you're not breeding you're not going to pass that trait on.
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What traits can one person possibly posses that need to be passed on?

...but doesnt answer the title of the thread?
 
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tantalus said:
no what I am saying is that the process results in heterosexual individuals retaining homosexual genes over evolutionary time, which they pass onto some of their offspring and that this disadvantage of producing offspring that will not pass on their genes (as they are gay) is due to some other related and tied beneficial traits which outweigh such a negative (in Lifetime reproductive success).The focus is not on why gay people continue in the evolutionary process as a distinct entity but why heterosexuals retain the gene over evolutionary time
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But how do offspring born with a gay gene, and thus I assume born gay, pass on ANY trait if they don't breed? And if gay people don't pass on their genes, how do heterosexuals end up having it? No trait will ever confer a selective adavantage if it is never reproduced thru heterosexual sex. And gay people don't have that kind of sex. Therefore they'd be wiped out, as well as the gene causing homosexuality.
 
There are a number of theories as to how homosexuality (or traits related to it) were adaptive in early human populations. I'm not expert on it, but all one has to do is Google "evolutionary biology of homosexuality" and you can find several hypotheses quickly.

For example: http://www.tcs.cam.ac.uk/uncategorized/homosexual-sapiens/

There are numerous hypotheses to explain the origins and maintenance of homosexuality which rest on a different aspect of evolution. There are also many that integrate different ideas and place them in the context of an ancestral human population. For example Rahman and Wilson proposed that feminine behavioural traits became adaptive in males as they would mediate aggression, aiding same-sex affiliation and the maintenance of alliances. Such behaviour was then selected for by females as it would reduce infanticide and facilitate paternal care. This perhaps resulted in a period of 'runaway sexual selection' allowing the spread of genes promoting homosexual behaviour maintained by balanced polymorphism, in the same way as sickle-cell anaemia alleles are maintained in malaria regions. Similarly selection for masculinising alleles in females may have aided intra-female alliances with "powerful females". This is just one of many suggested scenarios. Can evolutionary biology incorporate homosexual behaviour? There is a plethora of biological hypotheses to explain the origin of homosexuality which have a sound theoretical basis.
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Not that anyone can say for certain which, if any, is right.

The most common theory that I have seen is a version of the one above: that strong same-sex bonding is useful in a social species because it enhances group cohesiveness, and that homosexuality is the result when those traits become over expressed. That is to say, they liken it to malaria. Having one "gay gene" is good because it enhances the social bonds around you, but having two copies means you will prefer same-sex relations exclusively.
 
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