Debate:Does Darwinian natural selection suggest that homosexuality is bad for the survival of a species?
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Yes
This is an extremely complicated question, without a yes or no answer. First of all, if it were critical to the survival of the species for all members to be "genetically" hetero, then that trait would be gone by now. Obviously, sexual orientation is not a simple Mendelian trait...but if it were, posit the following..
First, many homosexuals reproduce, so fitness actually doesn't come into play. Second, there are several theories out there about how homosexual members of society help continue their own genes (nieces, nephews, etc) by helping the whole "tribe".
Anyway, there is NO simple yes/no answer.PalMDtalk 10:29, 31 March 2007 (EDT)
Well regardless of what Darwin has or has not suggested, clearly homosexuality is bad for the survival of a species. If we were all homosexual, we would all die. At least to my present knowledge two men or women for that matter cannot produce offspring. And until this is disproved, regardless of Darwin or anyone, a pure homosexual group and not survive.--JonL 12:13, 4 October 2007 (EDT)
- Yes, but, homosexuality is not passed on like eye color. Children of homosexuals are not exclusively, nor always homosexual. ChrisQ 20:16, 5 March 2008 (EST)
No
No, because otherwise how could homosexual penguins evolve in a New York Zoo?
No, because there is no such thing as a "specie". --Madonna 09:23, 3 April 2007 (EDT)
- Actually, there is. It just isn't the singular of 'species.' Tsumetai 09:44, 3 April 2007 (EDT)
- I guess I'd better clarify that. There is no such thing as 'a specie', because 'specie' is a mass noun. --Madonna 09:58, 3 April 2007 (EDT)
The question supposes that homosexuality is a genetic phenomenon, which isn't necessarily the case. However, if we make the assumption that there is a genetic basis to homosexuality then there are at least three mechanisms whereby there could be positive selection for homosexual genes: overdominance, antagonistic sexual selection and kin altruism
Overdominance: in this scenario homosexuality would require two copies of the homosexuality gene (hh), and someone with only one copy of the gene would be heterosexual (Hh). In the case of overdominance there would be a selective advantage for the Hh genotype for some reason. The classic case of overdominance is in sickle cell anemia where people with a single copy of the sickle cell allele are resistant to malaria, but people with two copies of the allele have a debilitating (and in some cases fatal) anemia. Thus, even though there is a strong fitness cost to having two copies of the allele, the allele is maintained in the genepool at high frequency because of the fitness advantage of having only one copy of it.
Antagonistic sexual selection: in this scenario the homosexuality gene would have different effects depending on the gender of the person carrying it. So, a male carrying the gene might be homosexual, whereas a female might not. If there is a strong selection pressure for females to carry the gene, this can counteract the adverse selection advantage of the gene in males.
Kin altruism: this was alluded to by PalMD. Ones siblings share, on average, the same number of genes as ones offspring. Therefore a gene which causes you to nurture your siblings will be selected for with the same pressure as one which causes you to nurture your offspring. It has been suggested that a homosexual gene may do this as instead of going off and getting married and having babies homosexuals would stay at home and care for thier siblings and other relatives.
Group selection: like the idea of kin altruism, an evolutionary explanation of homosexuality based on group selection would argue that a group of humans which includes some homosexuals has a higher probability of surviving, and passing on its genes, than one without. For example, if long ago humans lived in tribes, and those tribes competed to survive, then homosexuality might be favored by evolution if tribes with some homosexuals were more likely to survive. This might be the case if homosexuals helped care for heterosexual members of the tribe. Alternatively, a tribe might be more likely to survive if unattractive male heterosexual tribal members had a tendency to convert to homosexuality instead of causing chaos in the tribe by fighting against more attractive males.
For a short review discussing these scenarios see Sarolainen and Lehmann, Nature 445, 158-159. For further discussion and theoretical modelling of the various theories see Gavrilets and Rice, Proc. R. Soc. Lond. B 273, 3031-3038 and references therein.
Chrysogonus 12:16, 31 March 2007 (EDT)
First of all: Overdominance? While I will admit that your application of genetic principles is sound, you miss a crucial point in your argument here. What, exactly, would be the genetic benefit of having but one h gene? You make a clear case for why this is the case for sickle cell anemia, but leave out any reason why this would be the case for homosexuality.
- Scientists haven't figured out the function for numerous genes, and the phenotype of HH and hH could appear entirely unrelated, like sickle cell anemia and malaria, which are wholly unrelated. Scientists only figured out the connection because it's very simple, involving one gene, and easily testable. Gregory
Also, on the point of group selection, you state that "unattractive" males might convert to homosexuality as a means of avoiding confrontation with stronger rivals. This makes no sense. Nowhere do you state homosexuality is a choice (an idea I don't advocate as the sole reason for homosexuality, but one which must be mentioned in such an argument). How would this work, genetically, if we presuppose purely genetic factors as the cause of homosexuality?
- "Unattractive" males might not make a "choice" per se. It is possible that the increased stress of finding a mate (or lack of sexual release or something else entirely) when you are a poor choice for the opposite sex can trigger a gene that was previously inactive. Many genes are turned on or off at different times in a person's life. It could occur in childhood (or during pregnancy) too - if there are not enough eligible women for all the men, for example, the relative over-exposure to male pheremones in childhood could trigger a gene, or the stress of a woman being pursued by multiple men could cause a gene to be triggered in utero. Gregory
Thirdly, Darwinian selection covers far more than genetics. Social systems are on the chopping block as well. There needs to be consideration of social factors in this debate. Does the society allow for other outlets of pent up frustration? Is homosexuality taboo? Wouldn't homosexuality evolve itself out(excuse my poor phrasing) in such a system as you propose? Or are you suggesting that all males possess the "gene" for homosexuality, and like certain "lower" creatures can adapt their sexual presentation at need? I refer, or course, to the tendency for frogs to alter their sex based on mate availability. Or are you stating other factors? Please be more careful in your statements.
- I'm not really sure what you are asking here, and of course, I don't know what the original poster was referring to. But he was giving a few means by which homosexuality could have an evolutionary advantage in a tribal society. Obviously, other factors of the tribal society can override this (if homosexuality is a taboo and homosexuals are slaughtered as soon as they're identified). The point is that it is a way that homosexuality could evolve. Gregory
Lastly, Darwinism is as much about survival of the fittest individual as it is the species as a whole. How adaptive is it to through out a complete genetic loss like a homosexual in such sparse numbers as a means of caring for the "genetically superior" hetero population? Look at the central nervous system of our body. For every functioning neuron, there are several dozen cells providing support. Even the neurons at infancy reproduce far beyond the eventual number of functioning neurons in the infant's brain. That's because billions of neurons die because they weren't fit enough. Homosexuality doesn't fit so well with pure genetic Darwinism.
- But a homosexual's genes are just as successful if he or she has five children as if he or she contributes to the reproduction of five brothers or sisters. That's how vast quantities of bees are totally incapable of reproduction, for example - the genes that cause sterility occur along with genes that promote the species' survival. If the hypothetical "kind gay uncle" devotes his time and energy to helping his siblings raise their children, he has done just as much to promote his genetic survival as if he had children himself. Gregory
One final point. The Kinsey scale is a measurment of how "gay" a person is based on the number of heterosexual sexual encounters to the number of homosexual sexual encounters one has. Gayness isn't a pure thing. There are levels of variation in the strength of expression. This lessens the strength of the idea of the gay gene, for me at least. Perhaps gayness is simply a social construct, one constructed through behavioral imperatives forced upon our culture by a lack of mates. Who knows? Genetics is not an end all answer for gayness yet. We have to see what the research says.
- I agree that genetics is not an "end all answer" for homosexuality, but many genes features variation in the strength of expression. That's (in part) why people do not uniformly fit into "tall" and "short" categories, or "blond" and "not blond". Some people are kinda tall or "dusky blond". Gregory
--I Corinthianians xiii 14:29, 5 April 2007 (EDT)
What kind of a question is this? Our species is no more in danger of extinction
- we are always in danger of extinction.Jaques 03:55, 3 April 2007 (EDT)
- Speaking for myself, I think the question is related to arguments about whether the Theory of Evolution can be true, or is contradicted by something. Like, if ToE is true, how did homosexuals 'evolve'? Wouldn't they tend to die out since they don't reproduce?
- It is related, at least tangentially, to the debate topics, "Is homosexuality a perversion?" and "Is there in homosexuality an element of rebellion against God?" --Ed Poor 09:30, 3 April 2007 (EDT)
I would say no since the competition for resources are reduced by the population not over breeding. This has been seen in mice populations. When the mice population density is to a certain level there are higher cases of homosexual behavior. Some scientists believe that this is due to a switch in the genetic make up of the mice to induce population control.--TimS 11:15, 3 April 2007 (EDT)
Absolutely Not=
I would refute this claim, and refer anyone interested in this topic to read "Sperm Wars." It is a book written by a scientist who spent years researching men and women in their sexual relationships, examining their behavior and evolutionary reasons behind it. He postulated that homosexuality is actually beneficial to for the propagation of one's genes, provided that a man (or a woman) reproduces before adopting a homosexual lifestyle. The more this person reproduces before engaging in a monogamous homosexual relationship, the better. In doing so, he or she effectively sequesters another member of society from reproducing themselves. When primitive humans lived in smaller groups, this was a very effective way of ensuring that your offpspring were in greater numbers than your counterparts in subsequent generations.
Certainly, if the entire species engaged in only homosexual behavior, it would be bad. But there will always be an unbreedable portion of a species. Some humans are sterile, some beat their children to death, and some simply choose not to breed. Homosexuality is a way for a part of the species to NOT breed, so the population doesn't grow wildly out of control. In fact, it suggests that Darwinism is correct, and actions bad for an individual's genes might be good for a species.
The question is nonsensical. It presupposes that homosexuality has a genetic component (which is fine as an assumption for this discussion) but if that is true, then Darwinian natural selection would suggest that homosexuality (by its very existence) is good, or at least neutral, for the survival of the species. I think the person who titled this page really wanted to ask "Does the existence of homosexuality disprove Darwinian natural selection?". (Which, of course, it does not - even if we assumed that homosexuality always had a negative fitness cost, so does having an appendix. Neither one is evidence for or against natural selection in and of itself) Gregory
If anything, it's beneficial to have a gay segment of the population for humans. For one, we're overpopulated as it is, so gay couples who can't reproduce and as such may adopt is an advantage, allowing for better survival overall. Also, it creates another diverse group, which is something humans as a whole thrive on.
With regards to other species, the aforementioned group selection applies, in that gay noncompeting members may help with protection and raising of others. falco1029 23:43, 3 April 2009 (EDT)
Maybe Not
Maybe it's a response to overpopulation. We need to be in relationships to maintain our own happiness, but with 6 billion of us on a planet already struggling to support our needs, we don't need more kids!!!! Maybe more homosexual relationships are the way forwards!
lol i suppose so, if 80% of the worlds population was homosexual than their wouldn't be a population crisis in a few decades, but thats only in the case of humans and not in the case of animals, which don't have overpopulation Greenmeanie 23:57, 12 May 2008 (EDT)
How about you are all wrong?
Evolution does not act on the species level, it acts within species. A gene or cluster of genes which encourage there own survival will be more likely to be passed on to the next generation. Since homosexuality exists in such prevalence and is so obviously hindering to direct gene progression there must be some other reason for it. It could be demonic in nature (although if demons exist and are possessing things why bother with animals?) or more likely it has to do with other factors, like the immune system of the mother attacking male fetuses, or the higher fecundity observed in sisters of homosexual men. --Brendanw 15:56, 9 October 2008 (EDT)
natural selection works ONLY on individuals. A homosexual or in fact anyone who does not produce children is removed from the gene pool and becomes irrelevant to the species. Markr 14:08, 11 October 2008 (EDT)
- No, Natural Selection works only on Genes, not the bodies that the genes build. --Brendanw 20:05, 11 October 2008 (EDT)
