Thursday, August 18, 2005

Evolution and Homosexuality: Does one prove the fallacy of the other?

Over at Big Cat Chronicles, Roaring Tiger takes on LaShawn Barber's obvious gay baiting post on abortion and Homosexuality. This got me to thinking about something that has been percolating in my head for a while. Before I begin, I want to say that I firmly believe that evolution is real, and is the source of all life on this planet. Secondly I firmly believe that homosexuality is not a choice but is the result of a heretofore unknown confluence of one or more genetic, developmental, or both, influences. I firmly believe that RT did not choose to be a lesbian any more than she chose to be female. She is what she is and is happy with that. I have no problem with that, if only all of us were as happy with ourselves. These two views however have been argued by others to be mutually incompatible. If homosexuality were genetic, and homosexuality tends to limit the number of offspring, who in turn would tend to be homosexual, then those who believe homosexuality to be a choice (and further, tend to believe evolution to be a lie as well) argue that evolution would have over the centuries removed those traits from the gene pool. At first blush, this would seem to be a logical thesis. I however have to ask: What if there is an evolutionary benefit conferred by homosexuality? Or more precisely, what if the same traits (be they genetic or developmental) that can give rise to homosexuality confers some benefit to the species and it is only when other factors intervene that homosexuality results?
Let me give you an example to explain what I mean.

Northern European people tend to be light skinned, blue eyed and blonde. These all result from a lower level of melanin created in thier bodies. In the northern climes where these traits originated, the much shorter daylight length gave those who could see in low light an advantage over those who could not. Blue eyes confer an advantage over darker colored eyes in this regard. Additionally since there was less sunlight and it was colder leading to more clothing being worn, these people did not need melanin to protect them from sunlight. These two influences lead to the physiotype we see today. The DNA sequence that gives rise to blonde hair and blue eyes however, when damaged by UV light is usually mis-repaired by the body's repair mechanisms and it leads to melanoma. This is why light skinned people get skin cancer more often than darker skinned people do. So does that mean that all Blonde and blue eyed people will die of skin cancer? Of course not. And even if that were true, by the time melanoma killed them they would have likely as not lived long enough to have kids, passing those genetic traits along to thier progeny. Evolution would basically be done with them.

Now, with that concept in mind, let us return to Homosexuality. There is a branch of biology called evolutionary biology in which researchers try to approach the issue of development backwards. They look for what benefits a given gene might confer to a species and then tries to answer "what went wrong?" in an effort to understand the original purpose of a genetic trait that may be causing other problems, such as the melanoma example above, or the sickle cell gene (it confers resistance to malaria BTW).

I have to conclude that had there not been evolutionary pressure for this trait to continue to exist, it would have been wiped out thousands of years ago. Therefore I think the evolutionary biology approach might help to answer the question of why. What advantage does being emotionally attached (not sexually so much as emotionally)to members of the same sex confer? Not in todays society which is evolutionally speaking far too new to have made much of an impact as yet, but in the hunter gatherer society that humans existed in for millions of years before the advent of technology. Perhaps as a team building trait amoungst male dominated hunting parties? Or to help maintain societal order amoung female dominated encampments? Is it even more primitive? Does it arise from pack hunting societies of predators like wolves and primates where an "alpha" male and female control the rest of the group? Or is it an even more primative genetic holdover from the ability that some fish and amphibians have to change thier own sex based on environmental factors? I obviously do not have the answer, but I do believe that if we start from that perspective, we may find ourselves with a much better underlying understanding of what homosexuality really is and it's genetic and developmental underpinnings.

25 Comments:

Blogger Pigilito said...

Interesting idea. There are many examples of things which were once beneficial to our species, but no longer serve any purpose (e.g. a pathway to synthesize vitamin C once worked but now is inoperable). These examples remain in our bodies, but don't help us one bit.

On the other hand, I'm not sure a trait needs to confer an evolutionary benefit to be present. It may be that any gene leading either directly or indirectly to homosexuality is simply a relatively common genetic mutation.

In the end I hope not, because many on the religious Right will then agitate for research to prevent this "horrible genetic defect".

August 19, 2005 4:49 AM  
Blogger Rorschach said...

Pigilito, the idea that it is a somewhat common mutation of an otherwise beneficial (or at a minimum benign) gene I thought was implicit in my thesis, but perhaps I was unclear that was one possible explanation. I do not believe it is that simple however. I believe that, like we are now learning about most cancers, there are probably multiple pathways to the same end result and multiple changes/influences that are required to achieve it in each case.

You make a good point about those who would want to use this understanding to change, or as Ms Barber desires, selectively abort, children that MAY develop to be homosexual. However, I do not feel that possible outcome, however probable it may be, is reason enough to not try to understand the reasons behind it. That is like banning research into nuclear power because you can use some of the same knowledge and materials to build bombs.

I do not believe there is anything implicitly wrong with homosexuality. I do believe that society's viewpoint that it is wrong causes undue pain, anguish, and psycological problems for those people who are homosexual, whether they choose to admit it to themselves or not, and thier family and friends. And it can lead to self-destructive behaviors. Perhaps understanding it's biologic basis will move it more into the mainstream, much as understanding the biological basis for schitzophrenia or depression has over the centuries made society more willing to accept that it is not satan, it is biology at work.

August 19, 2005 9:31 AM  
Blogger Rorschach said...

Here is another thought. What if, in society's zeal to ostracize homosexuals, it is in actuality ensuring it's survival? Let me explain:

Many, perhaps even most homosexuals at first try to deny thier attraction to the same sex. Many try to "fit in" and get married and/or have children. Society's need to shame gays has then had the exact opposite effect than desired. People who might have realized thier same sex attraction and acted upon it at an earlier age had they not been ostracized, have now passed those traits on to the next generation. It might even be possible that as Homosexuality becomes more accepted, it may actually become less prevalent over time. This is assuming that there is at least some genetic component which I believe does exist.

August 19, 2005 9:52 AM  
Blogger Kathy Herrmann said...

Rorschach -- You've opened an interesting line of discussion. I'm going to give some time pondering your central question and may revisit with some other ideas but have a couple of ideas to add into the mix.

1) American Indian two-spirit tradition, sometimes called berdache tradition (This was a pre-European belief, which depending on the tribe morphed under Euro-influences): "Two Spirits" were believed to be people with two spirits occupying the same body (ie, having male and female traits). These folks were honored because the Amerindians believed them to be a go-between for males and females because of their ability to understand both sides of the gender divide. Before white influences, Two Spirits were often raised in the shamantic tradition and viewed as healers.

For those preferring it, strip out the spiritual connotations and what Two Spirits come down to are emissaries to smooth relations between men and women of the tribe. Also folks that help provide psychological or medical comfort on an individual basis as healers.

Also, I haven't seen it mentioned anywhere, but it would also make sense to me the Two Spirit men might have provided sexual services to warriors long away from home while traditional gender roles keep woman tending to homes.

2) The above idea is a spiritual view but another writer provided a mundane benefit of having homosexuals in a tribe. Can't remember which writer, though, but it might be discussed by Jamie Sams, a modern-day Seneca spiritual teacher.

As childless adults, homosexuals benefited the tribe because they could provide support to breeding adults, helping to shoulder some of the work needed to provide for a family, especially when the children were the youngest and most demanding. Help might come in the form of babysitting, hunting, gathering. That is, a variety of forms.

August 19, 2005 2:40 PM  
Blogger Kathy Herrmann said...

Just had another thought on the supporter idea of homosexuals. Wolves provide a similar example in nature.

The alpha mating pair are the only pair allowed to mate, unless the pair is weak and the lower ranks sneak in a mating or two. Granted the non-mating adults aren't gay but the significant point is only one set of pups is allowed birth at a time.

The lower ranked adults help in the distribution of labor to help ensure the pups reach adulthood. For example, the lowly omega is commonly the baby-sitter while alpha mom and dad get back to hunting.

August 19, 2005 2:56 PM  
Blogger Rorschach said...

The idea that childless homosexual individuals might serve as support individuals in primitive cultures is one possible reason why the trait has not died out. Much the same reason why humans tend to form extended families made up of grandparents and aunts and uncles etc.

There is another point that is somewhat related I'd like you to ponder and give me your opinion on. Is bisexuality the result of incomplete acceptance of an underlying homosexual nature or is it a completely different phenomena that merely mimics homosexuality? Perhaps as a form of non-gender specific nymphomania? Or something completely different? Or is it possible that one or more genetic or developmental triggers we have been discussing is either absent or attenuated inhibiting the "switch" per-se. Or is it possible that, for some bisexuals that the same sex attraction is a manifestation of thrill seeking behavior (doing something that is taboo, not because they perticularly enjoy the act itself but because they enjoy the thrill of doing something society frowns upon)

August 19, 2005 3:41 PM  
Blogger Rorschach said...

RT, also consider, that if homosexuality is hereditary (vs the result of a common mutation or due to developmental influences or a confluence of more than one of the above) then childless tribe members would not have the opportunity to pass that trait along. so while it might confer a benefit, I cannot see how evolution could select for it unless it is the result of two recessive genes that siblings with only one copy would continue to pass on.

August 19, 2005 4:54 PM  
Blogger Patrick said...

Hello, Roaring Tiger sent me your way. Considering the length of post I ended up with, she may regret that. Lol. It's a really interesting topic that I've thought about a great deal. But first:

For those preferring it, strip out the spiritual connotations and what Two Spirits come down to are emissaries to smooth relations between men and women of the tribe. Also folks that help provide psychological or medical comfort on an individual basis as healers.

Also, I haven't seen it mentioned anywhere, but it would also make sense to me the Two Spirit men might have provided sexual services to warriors long away from home while traditional gender roles keep woman tending to homes.


Native Americans had extremely diverse cultures. So the way a two-spirit was perceived and treated varied greatly. They were not always respected. Another thing, regarding "sexual services". Remember that they did not have the same concept of cut and dried "straight and gay" that our culture does. So straight men could and did have sex with each other pretty regularly. The gender of the person you had sex with did not determine ones identity. (It still really doesn't, but we don't see it that way.)
_________

Regarding gays, lesbians and evolution, what I've come to conclusion to over the years is that we are a genetic trait. Only it's not like having blue eyes, it's like having eyes in the first place.

Sometimes I think we sort of unconsciously assume that men and women evolved separately. Thats not correct, it's the human organism that evolved. That human being isn't necessarily male or female, but is simply human. And that human being, as an organism, has the ability, a survival trait, to break itself up into two or more kinds of variations on the basic human "type".

The evolutionary benefit passed down through the millennia is that capacity for two sexual sub-types.


This is bi-sexuality in the sense of having two different types of humans, each carrying half the genetic code for a new human, with in-built characteristics of stability AND mutation. Two or more copies of DNA information at conception help enforce that what is being created is a human. If one set is damaged, another set can correct the mistake. At the same time, the two or more sets of DNA create a new mix of genetic factors, some of which may be survival traits, a step forward in the evolutionary chain.

So these are some of the benefits of the human capacity for bi-sexual differentiation.


But what does that have to do with gay people?

Simple, the reason we exist is because of that bi- sexual capacity as I've defined it above.

We are the result of that purpose. Something to think about is that its becoming pretty clear that regardless of "nature vs nurture", that gay and lesbian brains possess both female and male characteristics in greater degrees than heterosexuals do.

Remember, every human has physical characteristics of both of male and female. To be blunt, this is why men still have tits and women have a clitoris.(Penile tissue).

Gender is determined at conception, however, for many weeks afterward the fetus is actually sort of blank, more resembling a female than male.

Only after the rush of hormones start kicking in do the male/female chromosomes really start coming into into play. And even after that, you are still rolling the dice as to what degree the child will have different male and female structures, especially in the brain.

So what I'm saying is that gays and lesbians are not an evolutionary trait in and of themselves, but that the reason we keep showing up, generation after generation, is because the survival trait that creates us is the human capacity for bi-sexuality as defined above.

That's why we don't breed out of the species, because in order for that to happen, you would have to remove the capacity for human bi-sexuality in the first place. And I don't see us becoming asexual organisms anytime soon.

Gays and lesbians, and everything in-between or to the side are all just variations of the human organism. One big happy set of humans. ;-)
______

There's a spiritual side to this, but I think I've hijacked the thread enough. If your interested, then check out my post on "The Blood of Eden". I'm sorry I don't know my html well enough to leave a clean link.

http://www.gryphmon.com/2005/07/the_blood_of_ed.html

August 19, 2005 11:32 PM  
Blogger PZ Myers said...

You're trying too hard. There are a lot of assumptions you're making.

1. I very much doubt that homosexuality is genetic. I am very suspicious of attempts to pin complex behaviors and desires on simple genetic causes. The simplest explanation is that it is an epiphenomenon, a consequence of many subtle interactions during development pre- and post-natally.

2. Even if there were a genetic bias, that does not imply that homosexuality has a selective advantage. Even genetically deleterious traits can be fixed in a population.

3. There is no reason to think it deleterious to reproduction. Homosexuals are quite capable of having children--procreation does not require that sex be enjoyed. A great many heterosexuals are abstaining from having children, but we don't argue that heterosexuality is a detriment to reproduction.

4. There are adaptationist models (that I personally find unconvincing) that postulate selective reasons for homosexuality. There are inclusive fitness explanations--childless homosexual uncles and aunts invest effort in their nieces and nephews, for instance. There are explanations that involve sex differences; the hypothetical genes that induce homosexuality in sons promote greater fertility in daughters.

I favor the idea that it is a product of generic mechanisms that promote social behaviors. We have general, inborn preferences to interact with fellow human beings and to look for sexual interactions (more than just sexual release--if it were all about the orgasms, we'd all just masturbate our way to happiness). We have vaguely defined mechanisms to give us predilections, that most often lead people to fixate on members of the opposite sex. But our brains are highly plastic, and sometimes individuals will instead orient towards members of the same sex (or to shoes, or rubber wet suits, or plush toys...). It all doesn't matter. So long as we have an urge to love one another, society and the species benefits, even if individuals often miss the optimal reproductive target.

August 19, 2005 11:32 PM  
Blogger Cynicus Prime said...

I was going to suggest that your questions ignore the existence of bisexuality and ignore its importance, but then you went right ahead and brought it up in the comments. Drats, foiled again! But though you did bring up bisexuality and its confounding of the questions here, you didn't really put forth a theory. I will.
There are a hell of a lot more bisexuals than anyone thinks. My own personal theory is that everyone is bisexual on some level, whether they know it or admit it. But I will compromise and accept that closer to 50% of the population counts. This doesn't mean that everyone is equally attracted to men and women (as I am), but I think everyone (or almost everyone) has to have at some point contemplated or engaged in or toyed with same sex relations or even attractions. But anyway. Back to genetics...
I think the (unacknowledged) widespread nature of bisexuality helps to propogate alternasexuality. If there is a "gay gene", then I see it as more of a dimmer than a toggle switch. If a mother and father are both 90% straight and 10% gay, then their children are some genetic potential to also be non-heterosexual.
Assuming that sexual orientation is on some level genetic, and given the fact that not everyone is 100% gay or straight (and as I imagine, no one really is), then it makes sense that some level of homosexuality will continue to propogate itself in human evolution. Anyone who procreates and is not 100% heterosexual passes on a potential alternasexuality trait.

August 20, 2005 12:02 AM  
Blogger Pigilito said...

Rorschach and RT,

Really nice discussion you started here. I had completely forgotten the idea of chemical and hormonal influences while in the womb. Thanks to PZ for bringing it up.

Of all the explanations, which is currently the most favored (perhaps it should be which has the most evidence)?

August 20, 2005 8:06 AM  
Blogger North Dallas Thirty said...

From a strictly biological standpoint, I could see homosexuality as having value if it were somehow beneficial for an organism to limit their population and the chosen means was to divert members into non-procreative intercourse.

However, I tend to agree with the wisdom that homosexuality is the result of a complex interaction of environment and genetic precursors. Moreover, I think it important that homosexuality is as much an attraction as it is a carried-out behavior; i.e., one may be attracted to men, but marry a woman and sire a child.

From a metaphysical standpoint, out of the Christian tradition, I would argue that homosexuality is a blurring as a result sin of whatever cut-and-dried reality existed within the Garden of Eden. That does not make of homosexuality a sin, inasmuch as heterosexuality as we know it would also qualify as a blurring, but it does explain some of the Bible's attitudes towards it.

August 20, 2005 9:03 AM  
Blogger Rorschach said...

North Dallas, I was consciously trying not to make a distinction between attraction and acting. For the purposes of the discussion one is as good as the other.There is another level of influence that I do not feel is getting the level of research it deserves and it has been touched upon a little earlier. Biologists are learning now that the genome has been mapped that genetics are not the only purely biochemical influences. There is a whole other level of influences called the proteome, protiens that influence the way genes are expressed. One protien may affect multiple genes depending on which genes are being expressed at any given time/place. This could be yet another place where the process might branch.

August 20, 2005 2:07 PM  
Blogger Kathy Herrmann said...

What a great discussion Rorschach initiated. My computer went down this weekend so I missed some great comments until now.

Regarding the bisexuality issue that several folks have brought up. Rita Mae Brown, author, has an interesting..ummm...metaphor/description for sexuality that she uses in several of her fiction books (Bingo comes to mind).

Suppose everyone has a blue dot on their forehead to signal their sexuality. Folks that are 100% hetero will have a dot that so blue as to be white. People who have had a stray homoerotic thought but no action with have increasing blue pigments until you "cross the line" to folks who take homosexual action, who will have quite a lot of blue pigment in their dot. Finally, folks who are 100% gay will have a dot so blue as to be black.

In Rita Mae's metaphor, most folks will have some blue in their dot.

August 22, 2005 8:32 AM  
Blogger Rorschach said...

Oh agreed! there is a complete spectrum of sexuality out there. I have one more thing to throw into the gender blender here. That is the issue of gender dysphoria. Conventional thinking is that gender identity and sexuality are different things. But I have to wonder are they really? If sexuality is a result of multiple developmental processes that can follow alternate paths, and gender identity is driven by similar alternate developmental paths, is it possible that they are different outcomes from the same processes that branch at different places in the process tree? Are they merely different manifestations of a single underlying process map? I.E. I wonder if it might be possible to treat it as a boolean logic problem were every possible known outcome appears in the thruth table, might it be possible to treat the process as a black box algorhythm with a known truth table and reverse engineer it? What could we learn about how human sexuality arises in this manner?

August 22, 2005 8:08 PM  
Blogger Rorschach said...

I also wonder if the "color map" RT mentioned would follow the statistical bell curve.... if not, why not?

August 22, 2005 8:11 PM  
Blogger Rorschach said...

If gender dysphoria is truly more complex than currently thought, perhaps that would explain the number of post-op transexuals that find that after all the carving is complete, they do not find themselves any happier than before. Perhaps the "gatekeeping" process is getting caught in it's own biases and is mis-diagnosing the "syndrome" as a result.

August 22, 2005 8:21 PM  
Blogger Kathy Herrmann said...

Couple of thoughts....

Bell curve: Anecdotally, I think Rita Mae's idea makes a lot of sense. If you believe it, then I suspect the true 100%-ers are in the minority and the bulk of the people fall in the middle ranges. Put the 100%-ers on the far ends of the bell curve and the fatter mid-ranges of blue dots in the highest part of the curve.

The Eastern and indigenous spiritual traditions tend to view people as having both masculine and feminine energies (the yin and the yang in Chinese traditions) which lends itself to diverse gender identities (and this is the more typical view in the Amerindian traditions). It seems to be mainly the Western, and I suppose Islamic, traditions that view masculinity and femininity in polar opposite terms of one or the other.

Which brings up the interesting question...How much is the religious right's opposition to homosexuality to do with a need to cling to the polarities (that is, put aside what "the bible says" and look at the issue as a deeper more complex issue related to the nature of the faith.)

August 23, 2005 8:42 AM  
Blogger Rorschach said...

I'm not so sure the distribution is Gaussian. After all, Homosexuals (at least the admitted ones) are in the minority. Something like 2-3% of the population if my memory serves (Which more and more often it does not! Man I hate getting older...). Even if we assume that there are 10 times more of y'all out there than is estimated, that still is only a quarter of the population. That would argue that the process of sexuality and gender identity, while it can be influenced to result other than "normal" (for lack of better words at the moment) outcomes, tends to result in heterosexuality, at least to some extent, more often than not. Now I admit, getting a good statistical count is frustrated by sociological factors. The ingrained bias against homosexuality in any form makes the reporting of the frequency of it suspect. I have a hard time believing a full half of the population is more than 50% homosexual.

August 23, 2005 1:21 PM  
Blogger Kathy Herrmann said...

No, I miscommunicated. I don't mean to imply half the population is homosexual. And you're right, a bell-shaped curve is probably skewed to the wrong shape for this discussion.

That said, I do think there are a lot more folks who have had homoerotic thoughts than the 5-10% who self-identify as gay.

As to how many? As you've pointed out, it's hard to determine based on folks self-identifying because of societal stigmas associated with doing so, especially for men.

Hmmmm. That raises an interesting science/sociology experiment. Take prisons, for example, where homosexual acts occur in higher percentages of the population than in society at large. It be interesting if someone could determine how much prison-inspired homosexuality is solely opportunisitic (no opposite gender partners) and what percentage results from prisoners giving themselves more permission to act on what might be normal impulses for them (but otherwise suppressed on the "outside"). I think I conveyed my question.

August 23, 2005 3:15 PM  
Blogger Rorschach said...

But again, if that person won't admit it to him or herself, how could we reasonably expect them to admit it to a complete stranger? I think I may have an answer to that question. fMRI can actually "see" thoughts taking place (to massively over-simplify the issue). I believe that if a large enough statistical sample of the population, gay and straight, and including those individuals that consider themselves transgendered and individuals that enjoy participating in any number of fetishes. Put them in the machine and show them pictures of attractive and nude men and women, both individually and mutually engaging in sexual behavior of all types. I believe it may be possible to at least on statistical levels to develop a data set that will help define what parts of the brain are involved with each type of attraction. Not just in what parts of the brain fire off when different images appear, but what structural differences there are as well. There have been some small limited studies in this vein, but I do not believe the studies have been large or thorough enough to give a good cross-sectional statistical image. What I believe is needed is a study on the scale of the original Kinsey reports. Or perhaps even larger.

August 23, 2005 8:37 PM  
Blogger Kathy Herrmann said...

There's been some attempt to study bisexuality that way and the studies to date are flawed.

August 24, 2005 12:14 PM  
Blogger Rorschach said...

That is my point. A.)the studies are too small, B.) there may be more than one way to result in bisexuality or homosexuality depending on which influences occur and when in the development cycle. and C.) the studies were too narrowly focused.

August 25, 2005 11:54 AM  
Blogger Rorschach said...

Clayton Cramer tries to address this on his blog too:

http://www.claytoncramer.com/weblog/2005_08_21_archive.html#112507073945813847

I sometimes disagree with him on things, but I still respect him. He points up some studies that tend to indicate there is something biological involved, and other studies that might contradict that. Sadly, he does not have comments on his blog, feel free to bring your comments back here to discuss.

August 29, 2005 12:53 PM  
Anonymous Anonymous said...

What if bisexuality helped men to travel greater distances in ancient times during a hunt? The men would be able to be sexually satisfied with each other and so they could hunt for longer times if necessary but because they would be bisexual they'd still have sex with women and propagate the species.

Female bisexuality would also be selected for because while the men were away hunting the women would still want sex and completely heterosexual women would have been more likely to nag their husbands not to go hunting for too long.

But bisexuality could be caused by not having some genes for homosexuality and some for heterosexuality, so in some cases a person would receive only the gay genes from both parents.

As a result there would be evolutionary pressure for bisexuality, which would sometimes give rise to homosexuality due to how things paired up.

If you think about this this kind of fits how some of the great male leaders in history, Alexander the Great, Claudius, Napoleon, and some people think Lincoln were bisexual. In hunter/gather days better hunters would be more likely to lead the tribe, so if bisexuality benefited hunting it would also select for a closer relationship between leadership qualities and bisexuality.

March 09, 2009 2:58 AM  

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