How did homosexuality evolve?

[Strange]

18 minutes ago, zedrexvsyrex said:

I believe that sexuality is the link between nature and nurture.

Therefore it has a genetic component. Therefore it evolved.

18 minutes ago, zedrexvsyrex said:

And while it may not explain all, it may account for a significant amount.

You would need some good evidence for that. My understanding of the experiments you are referring to is that they put animals in situations of extreme overcrowding etc. That does not correspond to how most people live.

18 minutes ago, zedrexvsyrex said:

Interestingly, the rise of social media coincided with the rise of sexual deviancy (sexual deviancy being defined in this case as non-heterosexual and/or cross-species sexual intercourse), which very well could be increasing social pressure. 

That is such an extraordinary claim, you had better have some extraordinary evidence. I suspect it is complete and utter bilge.

(Ignoring, for the moment, the grossly offensive use of "deviancy" to describe non-heterosexual relations.)

[zedrexvsyrex]

3 minutes ago, Strange said:

Therefore it has a genetic component. Therefore it evolved.

Socialization/nurture evolved FROM nature because it increased our chances of survival. I think that homosexuality evolved (what an oxymoron!) just as a byproduct of how heavily influenced we are by socialization. So in reality, it's not that non-heterosexuality evolved per se, it's just that altruism evolved (along with a desire for altruism), which I believe is a better way of stating the evolutionary mechanism at play. Not to mention, it assumes that all homosexuals are feminine, maternal, and nurturing in behavior which is a gross generalization anyway.

15 minutes ago, Strange said:

My understanding of the experiments you are referring to is that they put animals in situations of extreme overcrowding etc. That does not correspond to how most people live.

Overcrowding in a social sense. The mouse farms never reached maximal capacity, nor were they even close to it either. This makes it all the more interesting. There were more rodents than social roles could fill, which gave rise to the chaos. I wonder how much can be attributed to humans as well, with Dunbar's Number and all that. 

[Strange]

9 minutes ago, zedrexvsyrex said:

I think that homosexuality evolved (what an oxymoron!)

Where is the oxymoron?

9 minutes ago, zedrexvsyrex said:

So in reality, it's not that non-heterosexuality evolved per se, it's just that altruism evolved (along with a desire for altruism), which I believe is a better way of stating the evolutionary mechanism at play.

What evidence do you have for a relationship between altruism and homosexuality?

10 minutes ago, zedrexvsyrex said:

Not to mention, it assumes that all homosexuals are feminine, maternal, and nurturing in behavior which is a gross generalization anyway.

As well as being wrong. 

10 minutes ago, zedrexvsyrex said:

Overcrowding in a social sense. The mouse farms never reached maximal capacity, nor were they even close to it either. This makes it all the more interesting. There were more rodents than social roles could fill, which gave rise to the chaos. 

As that doesn’t correspond to how most people live (and homosexuality has existed at all times in all sorts of cultures) it seems utterly irrelevant. 

But feel free to provide some actual evidence. 

[MonDie]

I really wanted to note: I recently learned that birds and mammals independently evolved their sex-linked chromosome systems.  Mammalian gender is only as old as mammalia and the mammary glands that distinguish mammals (if they're female).  That was a bombshell IMHO.

Anyway, I know about the sexually antagonistic selection and kin selection hypotheses, but the presentation does seem slightly PC.  I guess it's that they are trying to show that homosexual genes could be equally adaptive rather than being these subpar genes that still lead to a sufficient, though reduced, level of fecundity that allows the genes to persist in the gene pool at a stable, but low, gene frequency.

Moreover, there might be an assumption that homosexuality is 100% genetic/heritable, but it might be closer to two-thirds or three-quarters heritable.  AFAIK the best measure of sexual orientation is the penile plethysmography, which rarely identifies middle-of-the-road bisexuals but does seem to often show some, umm, measurement unreliable and/or low-level bisexuality.  This is speculation, but if the gay gene(s) don't always result in homosexualiy, then the non-homosexual counterparts might have their own advantages.  I read that both women and gay men are diagnosed with borderline personality disorder at a higher rate, and both women and BPD patients do statistically score slightly higher on the Reading The Mind In The Eyes Test, which I know isn't supposed to be a personality trait.  We also have the historical evidence of castrated men who lived into their eighties or so (and I wish the same for BPD sufferers).  Anyway, if the non-homosexual counterparts were healthier, more social, or even more appealing, then it could be another explanation for the persistence of these genes.  Out.

Spandrels are an interesting concept in this regard.

But I might be proposing some kind of adaptively conflicted phenotype rather than a spandrel.

After all, that is why we have diversity, unless you're into eugenics.

[Ken Fabian]

On 12/7/2019 at 1:01 PM, MonDie said:

Spandrels are an interesting concept in this regard.

I'm not sure "spandrel" is the correct term for it, but I'm inclined to see the absence of a distinct fertile season as having favoured a stronger sex drive that is not clearly targeted.  The change enabled homosexuality as a side effect to increasing the overall urge for more frequent sex that is required to better ensure conception in a species with low fertility and fecundity.

Strong sex drives without a specific trigger or target may have led to raised rates of homosexuality, which might have been detrimental but because our ancestors were social - as per my previous comment - I think increased variability and flexibility for sexual attraction helped prevent that heightened sex drive from exacerbating conflict over mates by allowing other outlets for satisfying it.

Edited December 9, 2019 by Ken Fabian

[MonDie]

18 hours ago, Ken Fabian said:

I'm not sure "spandrel" is the correct term for it, but I'm inclined to see the absence of a distinct fertile season as having favoured a stronger sex drive that is not clearly targeted.  The change enabled homosexuality as a side effect to increasing the overall urge for more frequent sex that is required to better ensure conception in a species with low fertility and fecundity.

Strong sex drives without a specific trigger or target may have led to raised rates of homosexuality, which might have been detrimental but because our ancestors were social - as per my previous comment - I think increased variability and flexibility for sexual attraction helped prevent that heightened sex drive from exacerbating conflict over mates by allowing other outlets for satisfying it.

The problem is that both homosexuality and heterosexuality tend toward an exclusivity of preference.  Your hypothesis would imply a normal distribution or a skewed distribution, but penile plethysmographs show a U-shaped distribution.

I read Gould's paper years ago, but reviewing it I picked up the possible reference to Secret Mark via "St. Mark's Chapel".  If the structuralistic concept of a spandrel is theologically relevant, it might contradict the religiously conservative denial of the naturalness of homosexuality.  For you see, one could argue that Gould's structural approach emphasizes an opposite logical principle, namely the positive rather than the inverse (A so B, rather than not A so not B), which might give God a role in establishing these structuralistic principles which involve natural facilitators of organic structure (i.e. with any luck, A so B, B so C, C so D, ...) rather than a universal mechanism for overcoming the limitations (with natural selection and the anthropic principle, not A so not B becomes B so A).  Moreover, I would imagine that some structures which become contraining dead ends would be removed through group selection (A+...+D so no E (Dead End)).  If homosexuality and other trans-gender variations are a byproduct of human structure and human sexual dimorphism, then either these were part of God's perfect human plan or else the human plan was imperfect or even a dead end.  That is, if homosexuality is an inevitable manifestation of the human structural "plan", then either homosexuality is part of God's perfect plan or else the plan was imperfect or even a dead end.

In any case, I actually posted because I forgot to include a third interesting observation, which is that phermonal attraction is genetically synonymous with immune function (the major histocompatibility complex) and inflammation is exceptionally strongly correlated with the male-biased autistic disorder (https://www.google.com/search?rlz=1C1CHBF_enUS771US795&ei=fJ7uXcyhCJX_-gSxiKlg&q=inflammation+in+autistic+disorder+site%3Anih.gov).  I suppose trans-gender variations could maybe potentially be the byproduct of some kind of anti-autistic, anti-inflammatory adaption that coincidentally tends to flip the sexual preference.  I don't know, it's food for thought.  1:30 PM CST

**synonymous or homophonic, or just, being literal, pleiotropy.**  Another consideration is that we humans are accumulating mutations in genes involved in odor detection, but the waning adaptiveness of odor detection would not render heterosexuality non-adaptive.  If anything, it is the reverse that waning heterosexuality would mean waning phermonal functioning to the extent that sexual preference depended on it, ... if it depended on it.  2:00

[Xeno]

this issue has been defeated by human kind. I work in the DNA field and have noticed that DNA isn't just HARD coded but is seriously effected by environmental factors. One reason homosexuality might exist and be prevalent is due to environmental over population and stress (tested and recreated using mice). However, Homosexuality no longer means your genes can't be passed on directly as we can use in vitro fertilization with a sperm donor or using Surrogacy. 'Further more, science has a controversial 3 parent technique. This means that a child can be born with the genes of 2 men and a woman 2 women and a man. so....yeah we can make genetic human chimeras so that both of the couples are genetic parents for the child. So in the modern day Homosexuality has evolved due to science, in the past possibly need. sexuality is still a fascinating concept because of biological functionality. sex went from "i need to preserve my species, genes etc" to "this feels good". I'm less curious about homosexuality and more interested in bi-sexual mind sets. In my opinion people who are bisexual are superior as they can choose to have children or choose not to depending on various factors. they're perfect compliments to environmental factors, such as over population, lack of resources, disease and stress that could potentially lead to the perfect balance of the human race. But i don't actually know for sure, this is just my opinion on the matter. 

[Strange]

3 minutes ago, Xeno said:

One reason homosexuality might exist and be prevalent is due to environmental over population and stress (tested and recreated using mice).

I am not aware thaIs there any evidence that levels of homosexuality are related to population density or stress? I suspect not, as it has always existed in all societies.

[Xeno]

In a 1962 edition of Scientific American, the ecologist John B Calhoun presented the results of a macabre series of experiments conducted at the National Institute of Mental Health (NIMH).¹ He had placed several rats in a laboratory in a converted barn where – protected from disease and predation and supplied with food, water and bedding – they bred rapidly. The one thing they were lacking was space, a fact that became increasingly problematic as what he liked to describe as his “rat city” and “rodent utopia” teemed with animals. Unwanted social contact occurred with increasing frequency, leading to increased stress and aggression. Following the work of the physiologist, Hans Selye, it seemed that the adrenal system offered the standard binary solution: fight or flight.² But in the sealed enclosure, flight was impossible. Violence quickly spiralled out of control. Cannibalism and infanticide followed. Males became hypersexual, pansexual and, an increasing proportion, homosexual. Calhoun called this vortex “a behavioural sink”. Their numbers fell into terminal decline and the population tailed off to extinction. At the experiments’ end, the only animals still alive had survived at an immense psychological cost: asexual and utterly withdrawn, they clustered in a vacant huddled mass. Even when reintroduced to normal rodent communities, these “socially autistic” animals remained isolated until death. In the words of one of Calhoun’s collaborators, rodent “utopia” had descended into “hell”. You can read more about such experiments here : https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2636191/

 

most of his findings were simplified and narrow focused, much to his dismay when he died. but there have been tests that show crazy effects of both overpopulation, low resources and a combination of environmental stress. Think about an  a-sexual where does this fit in with pleasure, DNA encodes us to survive, mental health perhaps? but again mental health is affected by both environmental factors and stress. 

Edited December 10, 2019 by Xeno

[Strange]

1 hour ago, Xeno said:

most of his findings were simplified and narrow focused, much to his dismay when he died. but there have been tests that show crazy effects of both overpopulation, low resources and a combination of environmental stress. Think about an  a-sexual where does this fit in with pleasure, DNA encodes us to survive, mental health perhaps? but again mental health is affected by both environmental factors and stress. 

But there is no reason to think that any of that is relevant. We are not rats. We do not live in conditions so crowded that we resort to cannibalism, etc.

And you have not shown any evidence that homosexuality (in humans) has increased over time, or with increasing population density.

[Ken Fabian]

9 hours ago, Xeno said:

However, Homosexuality no longer means your genes can't be passed on directly as we can use in vitro fertilization with a sperm donor or using Surrogacy.

Lots of people who have "come out" as homosexual have had heterosexual relationships and borne children the traditional way. The notion that a preference one way means having it the other way is not possible and being homosexual means no children is false; I suspect a great many strictly hetero people are quite capable of having sex with their own gender if social mores and circumstances were different. And homosexuals can and do engage in hetero sex specifically for the making of children.

I think bi-sexuality is probably the majority, with hetero sex merely being the most popular as well as socially acceptable and ultimately, through engendering of children, the most satisfying. Those teenagers, as their sexual urges are emerging, that could feel no arousal through physical touch or aided by fantasizing - in either direction - will be the minority. Don't is not the same as cannot.

[Sensei]

8 hours ago, Strange said:

But there is no reason to think that any of that is relevant. We are not rats. We do not live in conditions so crowded that we resort to cannibalism, etc.

The reason for increased rate of homosexuality in the Calhoun's experiment is increased testosterone (or other hormone) level in the essential moment of embryo development. Overcrowded environment is just trigger of stress of mother during pregnancy. We can imagine limitless other sources of stress, like afraid of being single mother (unknown, unwilling to have children or dead partner) etc.

In other experiment, scientists working with farm animals, wanted to find reason of homosexuality of bulls (which rendered them useless). They ended up drilling holes in hundred chicken eggs and injected testosterone, and the all newly born birds were homosexual. They used chickens to have results faster (quicker reproduction). Experiment was repeated with other birds and they get the same results.

8 hours ago, Strange said:

And you have not shown any evidence that homosexuality (in humans) has increased over time, or with increasing population density.

To get such data scientists would have to live and work in environment were every homosexual person is revealing his or her preference without worrying about what people say or do (reminding you in some still primitive countries there is imprisonment or even death penalty for homosexual activity) for couple hundred years to be able to get meaningful statistical data. Working with animals is faster and they do not lie revealing true orientation.

[Strange]

1 hour ago, Sensei said:

The reason for increased rate of homosexuality in the Calhoun's experiment is increased testosterone (or other hormone) level in the essential moment of embryo development.

Still not relevant. 

1 hour ago, Sensei said:

To get such data scientists would have to live and work in environment were every homosexual person is revealing his or her preference without worrying about what people say or do

Nonsense. Apart from anything else, one could assume that the documented cases relate to a similar proportion of all cases throughout history. But there have been times and places where people have been open about homosexual relationships. Overall it seems that levels of homosexuality in history are roughly constant  

Anyway the implied claim by Xeno was that there was an increased level caused by massive overcrowding. With no evidence of an increased level of homosexuality (which you suggest is impossible to obtain anyway) and no evidence of that sort of overcrowding, it is a completely irrelevant argument. 

[MigL]

1 hour ago, Strange said:

Still not relevant. 

Why is it not relevant, Strange ?

Sensei implies that stress increases hormones which may result in homosexuality.
And that assertion seems plausible, as has been mentioned, causes for homosexuality could be genetic, hormonal ( in the womb ), environmental, or various combinations/degrees of the three. I certainly don't believe it's simply a mental ( preference ) issue, as in some people like 'sweet' and some others like 'savory'.
( It would be nice to see a source for the experiments you mention Sensei )
The fact that the stressor for the rats was overcrowding is the part that is irrelevant to humans ( although jails do seem to 'encourage' homosexual behavior, but that is probably attributed to other reasons ).
But as he mentions, stress can be caused by a multitude of factors, and that may be relevant.

[Strange]

7 hours ago, MigL said:

Why is it not relevant, Strange ?

Sensei implies that stress increases hormones which may result in homosexuality.

Because:

• We are not rats.
• We are not living (and have probably never lived) under those artificial levels of stress.
• If those experiments were relevant, we would see a correlation between levels of cannibalism and homosexuality. I am farily sure that isn't the case.
• As there is no evidence that levels of homosexuality have increased, we must always have lived under that level of stress, which is obviously nonsense.

That is not to deny that among the many factors that could affect someone's sexuality, stress could be one. But we would need to see evidence of that. Which is not what is being presented.

[Xeno]

2 hours ago, Strange said:

Because:

• We are not rats.
• We are not living (and have probably never lived) under those artificial levels of stress.
• If those experiments were relevant, we would see a correlation between levels of cannibalism and homosexuality. I am farily sure that isn't the case.
• As there is no evidence that levels of homosexuality have increased, we must always have lived under that level of stress, which is obviously nonsense.

That is not to deny that among the many factors that could affect someone's sexuality, stress could be one. But we would need to see evidence of that. Which is not what is being presented.

one thing you're doing is what the original creator of the experiment died regretting "narrowing your focus" you're dismissing ALL of the experiment by focusing on "over crowding" 

• you stated "we are not rats" that's like stating humans can't get stressed and "feel" overcrowded, while suffering some of the same conditions. while its true we are not rats,  the thought process of a human is vastly different. There are people who choose to be homosexual and people who state they can't help it , its just how they are. There are some people who put themselves through torture thinking they need to reprogram themselves because they're homosexual. My point being while I agree that this test wouldn't be exactly proportional to human causes in its entirety, its not so easy to dismiss just because "we're not rats"  we do share at least 1/4th of our DNA with rats. (just a fun fact) 
• You stated we're not and have never lived under those artificial levels of stress. my counter- War, Famine, disease, slavery = yes we have, and in some parts of the world still do. There are land disputes by native tribes in different parts of the world over resources all the time. which actually usually involve cannibalism. Secondly - prison.  
• Why would there necessarily have to be a correlation between levels of cannibalism and homosexuality? humans don't have to eat each other to sleep with each other, most of us have a moral compass that wouldn't allow cannibalism. Although it is still practiced in some parts of the world, mostly over resource disputes between tribes when food and other resources were/are scarce. Such as the pygmies being eaten by Congo rebels. 
• you stated there is no evidence that levels of homosexuality have increased, we must always have lived under that level of stress. Actually i think levels of homosexuality has probably decreased due to our modern advancements. We have so much less stress now. We have vaccinations and cures for sicknesses and diseases that killed hundreds of thousands. We don't have to go stab our neighbors in the neck with a spear because we suffered a crop failure in our kingdom. We're no longer eat up with parasites, cold, wet, and generally starving because we might or might not get to eat and living in a cave. 
• My last point, and the actual point and the point John B. Calhoun tried to make. Was the fact that it was a combination of things that caused the increased homosexuality. 1: yes over crowding was a factor, but there was competition for food, for sex with females to reproduce, for nesting grounds, for property. In crowded conditions disease and sickness spreads like wildfire. Just interacting with a female could have possibly meant having to fight your way past 6 other rodents. Not all builds are equal - the bigger and meaner the better (alpha  and beta). If you have to fight Hercules to get some booty from Sarah and you know you're going to die, a solution might be to just bang Jim. The testosterone levels must have been insane not to mention the flood of adrenaline and dopamine. This experience left many rats asexual <- this is the most interesting outcome for me personally. The surviving rats were so traumatized that they turned into anti social a-sexual's that could no longer integrate with society. This made me think, WAR. these rats must have went through something akin to literal war.
• An interesting study which includes the use of dopamine and Oxytocin https://www.iflscience.com/brain/sexual-preference-rats-influenced-oxytocin-and-dopamine/.
• Amazingly, the effects of the hormones and drugs were not just limited to behavioral responses, but also changed the physiology of the rats' brains. It has long been thought that a region of the hypothalamus in the brain, the sexually dimorphic nucleus of the medial preoptic area (SDN-POA), is related to sexual preference. For all species of mammals so far investigated, it has been shown to be sexually dimorphic, with the male SDN 5-7 times larger than the females. This is thought to be related to the amount of testosterone experienced during the first postnatal days. During the experiment, the researchers found that those rats treated with oxytocin saw their SDN shrink. This specifically can tie Us as humans in with this experience as we are mammals, and we have testosterone. 
• One reason your research may present the fact that homosexuality has been constant even with a rise in population is due to reduced stress and a gain in resources. Which was explained above. Everyone is looking for increases without taking the fact of what we as modern day people have achieved.