Homosexuality--An Evolutionary Attempt

The reason that Homosexuality exists is to expand the human genomic sequence, through adaptative changes towards hermaphroditism-- natural selection that will allow for pyhsical adaptations, that will subsequently allow for procreative events that will transmogrify the human species into a variant species and branch it's own path in the evolutionary tree.

The copulative desire must be a precursor to pysical adaptations to ensure that if and/or when natural selection occurs, the process will be successful.

In the evolutionary grand scale, not all species that are hermaphroditic started out that way. Earthworms for example, who are both male and female exhibit this characteristic.

Life is ever evolving. Look at how bacteria have evolved resistence to anti-biotics. Examine the current fear of avain flu. The fear is that an evolutionary adaptation is about to occur in which it will jump from animal to human host.

To believe that Homosexuality is not natural or not supposed to be, is likened to thinking you are in a geocentric universe, when really you are in a heliocentric universe.
http://www.phxnews.com/fullstory.php?article=28445

to think that Homosexuality is a conscious lifestyle choice, it's been around for thousands upon thousands of years...and marginalizing this group is another example of fundamental tactics...

they think that if it was genitic it would have weeded itself out since homosexuals cannot procreate. This is their best defense. LOL

Only if it were truly "polar". The fact is that most people are somewhere on that sliding scale, and therefore if there is a gene that codes for it, it will continue to pass along the human gene line since we ARE in fact reproducing.

Assuming that a large percentage of homosexuals would not be reproducing.

I only wish it could control the population growth of Repiglicans...


Then again, given enough time and enough guns, they will more than likely do it themselves.

Sorry to jump on that nice notion, but anyone who tries to find a future purpose to current phenotype seriously misunderstands evolution. Evolution doesn't anticipate. The current mix of features in a species is a result of its evolutionary history, and not an attempt by individuals or the species or some evolutionary purpose to achieve some future state. Sometimes adaptations serve future niches well. Sometimes they don't. Extinction is also part of evolution.

Yes, homosexuality is natural. It is observed plenty in nature, across a wide range of species.

My own convictions are that homosexuals should have the same political rights as heterosexuals, including to marry and adopt. But that is a normative statement of a particular political viewpoint, and is not and cannot be derived from science. Science doesn't and can't determine a moral outlook. Hume figured that out more than two centuries past.

The author is working hard to make "natural" or evolution into a normative statement. Homosexuality is indeed natural and at least as much a product of evolution as anything else, but that only means that IT IS, not that it is part of an evolutionary adaptation, and no inference from natural or evolution can be made with regard to rights.

the "should be's" of nature, and those are all anthropomorphizations of nature's "intent", tinged with contemporary social biases.

We look at gay men as feminine or weak today. The greeks did not look at gay soldiers as feminine OR weak, rather as something to be feared and honored in battle.

We look at lesbians as "masculine" or "flawed" women, because they're not what they "should be", according to 21st century sensibilities, bubble gum chewing booby bouncing male worshipping airheads. :hide:

Hermaphroditism? Huh? There's that stereotype thing about gay men not really being manly men . . . about lesbians not really being female girly women, and both perpetuated by a paternalistic society.

I think the premise of that study is fairly flawed.

If you're a guy or a gal and you can get your rocks off yourself, it stands to reason it's not such a big leap to do it with someone else of the same sex, or of the opposite sex.

It's not polar for everyone - it IS natural because we all have this drive to reproduce coupled with the feedback mechanism of orgasm, and that reinforcement also reinforces the sexual and emotional relationships we have with other humans.

All the bullshit about "them" and "us" that perpetuates the idea that you are either all one thing or all the other are learned behaviors, just like accepted "feminine" and "masculine" behaviors are. A lionness is just as efficient at killing as a lion.

Just doesn't exist there.

it's talking complete gibberish. It's not 'science' - it's gobbledygook.

...that explanation makes absolutely no sense.

The most persuasive (although not totally convincing) evolutionary explanation I have yet heard for homosexuality was in the book Adam's Curse by Bryan Sykes. It's been a while since I read the book, and I don't remember all the details, so I doubt I will do his explanation much justice here. I suggest that everyone read the book to get the full story. Still, I'll give it a try.

Homosexuality is very difficult to explain from an evolutionary standpoint, because of a very basic fact about evolution. If a particular gene decreases the reproductive success of the carrier, that gene will be removed from the gene pool fairly quickly. While it is true that homosexual men do often have sex with women, and it it is true that plenty of homosexual men have children, there should be little doubt that homosexual men as a group are unlikely to reproduce at the same rate as heterosexual men. This is a evolutionary conundrum.

Sykes notes that the gene or genes for male homosexuality seems to be passed along the female line, from mothers to their sons (and from mothers to their daughters, who are carriers of the gene). Studies have shown that gay men are *not* more likely to have gay fathers than heterosexual men, so it's unlikely that the gene came from the father. Studies have also shown that gay men *are* more likely than heterosexual men to have gay uncles on their mother's side of the family. This pattern strongly suggests that the gene comes from the mother.

This suggests two things: 1) The gene may actually exist in our mitochondrial DNA, which is passed exclusively from mother to child, and is not mixed with the father's DNA; and 2) it also suggests that the gene may increase the reproductive success for the women who carry it -- in the form of greater success for their daughters.

Sykes suggests a possible advantage for those daughters. Because gay brothers are less likely to have children of their own when they grow up, those gay brothers have extra time and extra resources to devote to helping their mothers raise their sisters. This additional nurturing that the sisters get from their gay brothers increases their chances of survival, and increases their reproductive success.

And of course, those daughters pass the gay gene on to their own daughters and sons, and the cycle continues.

Sykes provides a biochemical explanation for how this gene might work, but I don't remember any of the details.

Obviously, this is a highly controversial topic, and there is no scientific consensus at this time. But this is the only convincing evolutionary explanation I have yet heard.

The hypothesis would seem to fit with a number of facts, but it would be surprising to learn that mitochondrial DNA actually has behavioral consequences. mitochondria have evolved mostly for the purpose of effecting oxidation and the two membranes are selectively permeable. This would seem to limit the potential for this sort of thing, but molecular biology turns often on very subtle effects.

One can easily imagine selective pressure that favors gay people. The obvious merits of this strategy biologically is represented by the case of bees, ants and termites wherein the vast majority individuals do not engage in procreative behaviors so much as to provide for the survival of (rare) individuals who do.

I am not gay, but I note that as the world is experiencing a crisis definitively linked to largely uncontrolled population growth, it would be well for all cultures to celebrate our gay people rather than to vilify them.

Like all hatred, the hatred of gay people is outrageous.

My memory of the biochemical explanation is extremely fuzzy. I would strongly suggest you pick up the book for his full explanation. I'll try to explain what I remember...

It is possible that Sykes did not specifically finger the mDNA as the culprit. This is going to sound even stranger, but here goes. The actual culprit may have been something else in the chemical makeup of the cytoplasm in the egg. During fertilization, the father only contributes DNA. But the mother contributes more than her DNA. She also contributes the cell and everything in it (including the mitochondria). So -- as strange as this may sound -- the "gene" in this case may not necessarily be the mitochondira, but could even be something related to the chemical make-up of the cytoplasm, which is passed directly from mother to daughter without any contribution from the father, and through repeated cell division is present in all the cells of the body.

Whatever the culprit, he makes a very convincing case that the "gene" for male homosexuality is passed along the female line. Sykes makes a comparison to a type of "male-killer" gene, which seems to exist in some human female lines in which female children greatly outnumber male children. The gene actually tries to kill male embryos. For those of you familiar with "selfish gene" theory, this would be in the interest of the gene because the male-killer gene is passed along the female line. Giving birth to a male would be an evolutionary dead-end for a male-killer gene. And each male not born leaves room in the family for more daughters to be born, thus maximizing the spread of the gene.

Sykes sees the gay gene as a sort of delayed-action "male-killer" gene. But instead of keeping males from being born, it makes them so that they are more likely to contribute to the raising of daughters.

Sykes does not argue that this gene directly controls behavior throughout the lifetime of the gay male. Instead, he argues that if the gene (or the biochemical process it influences) is present at the appropriate moment during the development of the embryo, then the brain will develop differently, thus influencing sexual orientation later in life. For all we know, it could be a process that lasts for only a few hours or a few days during the development of the embryo. During the process of embryonic development, different genes are getting turned on and off all the time, and the brain is constantly being flooded with different chemical signals which lead it to develop in a certain way. Even though the critical moment for the development of a particular behavior may be very short and very early in development, the results can be profound and may not show up for years after the child is born.

Interestingly, Sykes notes that there are different rates of homosexuality in first-born males when compared to males with older brothers. He argues that this may indicate some sort of biochemical reaction similar to an immune response, where the mother's body reacts in one way the first time it encounters the process, but reacts differently each subsequent time because it is now primed to respond. I don't remember if first-born males or males with older brothers were more likely to be gay.

ON EDIT: With regard to bees, ants, and termites, the fact that most members of the community do not actually participate directly in reproduction is explaned by the consequences of their reproductive system. I can't remember which book I read about this -- It was either "The Selfish Gene" by Richard Dawkins (amazing book), or "The Diversity of Life" by Edward O. Wilson. Anyway, the point is that due to the whole single-reproducing-queen organization of ants, termites, and bees, the resulting children are actually more closely related to the non-producing workers in the colony (they share 2/3 of their genes) than if they had directly participated in reproduction (where they would only share 1/2 of their genes). This is also a closer level of relatedness than mothers and their children of other species that use the more traditional "everybody reproduces" model (where they share only 1/2 of their genes). I couldn't possibly explain how it works out this way without cracking open a book. But the explanation was very sound in terms of mathematics and game theory. Since Humans use the "everybody reproduces" model, there really isn't any obvious evolutionary advantage to any individual that reproduces less than any other.

hypothesis about selection pressure.

I recall reading somewhere that gay behaviors are actually observed in many species. If so, then the co-incidence of this behavior in species that devote large efforts in the rearing of the young would support this idea.

It is difficult for me to imagine a mechanism by which the composition of cytoplasm - which is mostly a function of genetics in any case - could be involved in such a complex behavioral outcome as is represented by sexuality - particularly human sexuality. This is not to say that such a mechanism does not exist - I am no expert - but it does seem unlikely to me, at least without some kind of mechanism for amplification. The most common means of biochemical amplification is itself genetic of course.

If it is true that the propensity for being gay is in fact genetic, and further that this phenotype is carried mostly through matrilineal inheritance, yet another mechanism suggests itself besides mDNA or cytoplasm, that being the presence of this gene being found on the portion of the X chromosome that is unpartnered on the shorter (and largely degenerate) Y chromosome. This should not be surprising since this gene is obviously involved in all sexuality. This is precisely the mechanism that accounts for the predominantly male genetic syndrome hemophilia, as is well known, the most famous person to have carried this gene being Queen Victoria. Were this the case, however, the outcome should be measurable by statistical means - one would suspect that the incidence of lesbianism would be some fraction of the incidence of gay males (if in fact lesbianism and gay male sexuality have the same origins and are in any way related). I have no idea about the relative incidence of gay male sexuality and lesbianism. I'm not sure that anyone does.

I think that there as been many attempts to identify sexuality with brain or other morphology - but if I remember well - these attempts have been the subject of some scientific controversy and have largely been inconclusive. Probably such a study is a very difficult thing to quantify objectively - particularly because of the cultural imperatives that often obscure sexual identification: The true incidence of being gay is almost certainly higher than is self reported.

For most of my life I have been very suspicious of behavioral genetic reductionism, and to some extent this is still true. My position on this matter has been somewhat relaxed by the fact that I am now a father. In particular my sons have certain behavioral characteristics that I strongly identify with my own father - even though the boys unfortunately never met my old man, as he died before they were born. Although my own personality represents one mechanism for the transmittance of these behaviors - I have my reasons for believing that genetics represents a better explanation. This impression is however anecdotal and highly subjective, as opposed to systematic, as well I know.

That is a really interesting point that homosexuality might be more prevalent in species that devote large efforts to rearing young. Someone should do a study to see if homosexuality is more common in such species.

Anecdotally, I have heard that homosexuality is common in Chimps and Bonobos, who devote large amounts of time and effort to rearing their young (and who are the two species most closely related to humans).

ON EDIT: Regarding behavioral genetic reductionism -- the nature v. nurture debate has been going on for a long time, and will likely go on forever. I believe that genes do not entirely determine behavior, but the more I read about the topic, the more I am convinced that genes play a powerful role. I kind of like the metaphor that Robert Wright uses in his book "The Moral Animal." He compares genes to a set of pre-set dials indicating an individual's inclination to a particular behavior. If your "dial" is pre-set to "one" or "two" then you are less inclined to a particular behavior than if your "dial" is pre-set to "seven" or "ten." Through nurture or free will or both, an individual is able to choose their own behavior -- but different individuals have a stronger inclination to certain behaviors.

I should have made it clear that when I said homosexuality is "obviously" genetic, I was stating my own opinion. It will not be "obvious" until/unless someone actually finds a gay gene, and even then there will be plenty of room to argue that nurture plays a powerful role.

Since men get their only X chromosome from their mother, while women can pass it on to all their children.

Placement of the "gay gene" on the X chromosome would provide a possible explanation for the (apparently) different incidence of homosexuality in men and woman. I don't know what the percentages are, but my understanding is that homosexuality is significantly more common among men than women. In other sex-linked traits, like hemophelia, the gene is expressed much more often in men than women because men have only one X chromosome, whereas women have two and the gene must be present in both in order to show (which is very unlikely unless you are of inbreeding royal lineage).

I can't really think of any reason why the X chromosome wouldn't work. The X chromosome is not pass entirely down the maternal line. But in my (extremely non-expert) opinion it comes close, since it can't be passed from fathers to sons. Pure speculation here: I suppose it is possible that some mechanism could arise in (some but not all) men to somehow influence the mixing of genes from his two X chromosomse or to favor the passing of Y over X if there is an evolutionary pressure to do so -- pressure that might exist in the presence of a gay gene on the X chromosome.

I don't think Sykes discusses the possibility of X-chromosome inheritance in his book, but my memory could be wrong on that. It is entirely possible that Sykes chooses mDNA as the possible location for the gene simply because that is the area of his study. (He does a lot of work using mDNA and the Y chromosome, both of which are very useful for tracking mutation rates and paterns of heredity because they are passed exclusively along single-gender lines and are not mixed at any point in reproduction.)

Is that there are kinship patterns in which the sister's children are viewed as a brother's responsibility. These patterns were prevelant in the Melanesian islands, and can be found in pre-Mycean cultures in the Mediterranean.

It does not, by the way, seem to me completely evident that the matter is wholly or even mostly genetic. At this stage in our knowledge, tracing any particular complex behavior in humans to genetic roots has a "just so stories" air about it to me.

My view is that it is simply an essentially random variation in sexual socialization. Sexuality serves human beings for much more than procreation. It is an essential element in bonding a mating pair through time. It serves as a social lubricant and anodyn for many emotional conditions. Humans operate by symbols representing reality in their minds, rather than through direct experience of reality, and everything humans do, no matter how basic the urge the action satisfies, comes to be laden with symbology: the transformation of hunger into gourmandizing is a good example. The essential quality of symbols is that they stand for things, and what stands for one thing may well be perceived as standing for something else in another mind, and what is symbolized by one thing to one may well be symbolized by something else to another. Such sexual symbologies are refered to as fetishes when they are not particularly common, or are seperated from things that are obviously sexual in themselves, but that is too limited a view of the phenomenon. Heterosexual persons simply fetishize the sexual elements of the opposite sex, and because this is the most common usage of the sexual "language", their doing so excites no particular comment. But not everyone will seize on the same usages in any language, and that is as true of this one as of any other. Some will seize instead on a particular object, or on a particular activity, or on just about anything the mind can conceive, and among these things will be persons of their own sex, or genitals and body-parts similar to their own, rather than opposite to them. It does not need to serve any particular purpose, any more than a deep feeling that, say, maroon or steel-grey is just the most beautiful color in the world has to serve any purpose. It will simply occur to some number of humans that that is the case, and as long as humans continue to be born and raised, it will continue to occur to some of them. These are not concious choices, but felt things that impose themselves on people quite independently: no one decides conciously what strikes them as beautiful, anymore than anyone decides conciously what strikes them as tasty.

I was not aware of that.

Regarding the question of whether homosexuality is wholly or even mostly genetic, I have clarified above (Post 19) that that was a statement of my own opinion. It is certainly possible that it is a random variation of sexual socialization, but personally I do not find that to be a compelling explanation. Sexual preferences are more intense and more directly linked to reproduction (and evolution) than other preferences, so it seems to me that orientation would be more hard-wired in us than our preferences in color or food.

is the societal disdain for 'gay' children. Evolution, in this case, may provide a 'neat' explanation for gay children, but society, through religion, can and will suppress that thought, even in scientific circles where that thought should be free and intellectual.

Religion has been used as an excuse to suppress all sorts of perfectly normal behaviors. I would argue that deliberate suppression of those who are "different" or behaviors that are "different" is a common trait of human society in general, and is not unique to religion or to the religious. But it is true that religion is very often the excuse that is given for this type of suppression -- in fact, in many societies (including our own) it seems to be the most popular excuse by far.

But in the context of an evolutionary discussion, I don't think that suppression by Religion, or even by the enforcement of arbitrary norms or taboos by human society would have had a significant impact. Evolution works on extremely large timescales -- hundreds of thousands or millions of years. Based on the fact that Chimps and Bonobos also engage in homosexual behavior, I think it's fair to assume that homosexuality existed in our common ancestor 7 million years ago or more. So my best guess is that homosexuality predates religion by millions of years, and (IMHO) will likely outlast religion as well.

While I know we have some real religious extremists in charge of our country right now, and there are plenty of reasons for pessimism, my impression is that the long-term trends quite clearly show adherence to religion is going down while acceptance of homosexuality is going up. In fact, these trends are moving extremely fast when compared to evolutionary timescales.

bothers me.

It's great that people are looking into the hereditary aspects of same-sex attraction, and I love learning about how or bodies work. However ... there is often and undercurrent of implication that same-sex attraction needs to be justified.

Sure, if a gene can be found for it, then it is provably wrong for gays to be discriminated against.

But gay people should not have to be justified. They are not evil, they are not harming anyone. Quite the opposite, by working and not having children, they are contributing to the country's prosperity, their taxes are helping fund other peoples' children, and they are not contributing to overpopulation.

I believe it is my right to have a relationship with a girl or a guy, provided it is a situation unlikely to lead to hurting anyone, and that my choices are my own business. I consider myself heterosexual, as a rule, but I once fell in love with another woman and we had a wonderful, and for me, very educational relationship. And baby jesus didn't cry, no puppies died, and I still have not been struck by lightning.

Underneath, we are all just people, and what is important is how we treat our partners, not what orifice gets fucked with what.

There is no need to justify people's likes and dislikes. Whether homosexuality is nature or nurture or even a choice should not matter. Discrimination is wrong, period. And it is the right of any person to engage in whatever presonal relationship they please, provided that it does not harm anyone else.

But I must admit a fascination with the broad question of why things are the way they are. It's why I love science. It's why I am more likely to read non-fiction than fiction. I have no particular interest in this specific topic. But I do enjoy (to borrow a phrase from Richard Feinman), "The Pleasure of Finding Things Out."

I admire you and how you handle this web site. Like I said, you are one cool dude.

Now, this issue of homosexuality will politically kill you. It requires you to take a side. I would encourage you to take the side that is popular, as that's what's most likely to win elections. On the down side, that position is likely to kick me right in the face, but that is what may get the most Democrats elected!

Can I say that this will start any true change towards minorities? I don't know. What I do know is that the party for change has to be for all the people to change.

Only heritable characteristics could partake in evolution. This is not to say that homosexuality (or heterosexuality or bisexuality or what-have-you) is an "acquired" characteristic. You will always have gays and straights and everything in between and beyond.
My two cents.

I have always prefered long-term monogamous relationships. I enjoy football and beer, and I adore Golden Labs.

Did I somehow get a Lesbian gene? And is it contagious? My friends are worried...

For animals with complex social behavior, homosexuality may provide a number of different advantages depending on expression. Sexual and emotional alliances are the basis of many group dynamics, so any variation introduced into those dynamics is going to have multiple repercussions.

Just recently I've been pondering the ways in which male dominance is affected by homosexual behavior because of the behavior of two males dogs in my household.

Our adult Lab has always been a most reluctant alpha male in the pack. By virtue of being the only male for the last five years, he was "it", and you could tell he tried to live up to that role, but it made him very anxious indeed. Our two female dogs adore him and he's always loved the attention, but he'd much rather hide under the kitchen table than meet strangers. He'll bark for as long as his nerves can stand it, then he bolts to safety and lets the girls do the scary stuff, like getting petted.

Enter young male puppy some two months ago. The Lab fell like a ton of bricks for this stocky, strutting macho boy. Aside from drooling all over him and play wrestling with him, the Lab also... ahem...services him. Constantly. And the puppy does not object, let me tell you. At the same time, though, the puppy shows considerable interest in the female dogs, so he's willing to swing any way available to him.

Which got me to thinking about how "extra" males manage to cement their position in a pack ruled by an alpha male. Pack membership increases a male's chance for survival while providing the pack with an extra useful hunter. So a homosexual bond with the young dog who will assume the alpha role gives the Lab a protected position. He isn't competition for the top dog dominance spot -- he never wanted it anyway. And he's sexually uninterested in the female dogs, so he's not competition in that arena. The girls like him, the alpha dog likes him -- and the pack is all the stronger for this non-threatening member.

That's a pretty good survival tactic for the pack as a whole, even though the individual dog may not pass on his genes.