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    Gerhard Adam's picture
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    Just to kick things off, I'd be curious to know what people's thoughts are on the role of biological evolution on human behavior.

    There are so many quaint "just so" stories floating around, there's got to be someone willing to take this subject seriously.

    For starters, two questions come to mind.

    (1)  Evolutionary Psychology presumes that male behavior is based on the notion that there is a minimal investment in reproduction and therefore they will tend to mate with as many females as possible.  Of course, real world experience indicates otherwise, so why should this view be so prevalent?

    (2)  Another topic that came up in a discussion was whether our food choices/preferences are biologically determined or whether there is a equal or greater cultural influence at work.
    Mundus vult decipi

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    KRA5H's picture
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    "there's got to be someone willing to take this subject seriously."

    The only folks who take this seriously are those with advanced degrees in EP.


    "Evolutionary Psychology presumes that male behavior is based on the notion that there is a minimal investment in reproduction and therefore they will tend to mate with as many females as possible."


    As you point out: "Of course, real world experience indicates otherwise, so why should this view be so prevalent?"


    How would a EP practitioner demonstrate that this behavior is anything other than cultural?


    "Another topic that came up in a discussion was whether our food choices/preferences are biologically determined or whether there is a equal or greater cultural influence at work."


    I think this would be easier to tackle: compare human teeth (omnivore) to, say, goats teeth (herbivore)


    vegan, vegetarian, etc. are cultural.


    If the question is about, say, preference of chocolate over vanilla ice cream, chocolate wasn't available to Europe until the 1500s.








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    Gerhard Adam's picture
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    Regarding the food choice, the original issue was whether our concepts of disgust were biological or cultural.  In particular, one point was made that our specific tastes evolved so that we could select foods that were good for us.

    Yet, I have a problem in such simplistic judgements because there is no evidence to support the idea that our ideas of sweetness or sourness, etc. are indicative of "good" foods versus something that we are simply used to or have been culturally primed to eat.
    Mundus vult decipi
    KRA5H's picture
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    There is a claim (going from memory) that Lactase persistance developed about 30,000 years ago in humans, but was nonetheless cultural (evidently, that was when humans began herding cattle). 
    Those who are lactose intolerant would wish to avoid milk products.

    Foodies would have to argue good versus mediocre. 

    People who take survival training discover that there are all sorts of sources of food in the wilderness that urbanites, suburbaites would not even recognize as food or turn their noses up at it.
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    KRA5H's picture
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    Gerhard, 
    My previous post was a bit incomplete. the basic tastes Sweetness, Sourness, Saltiness, Bitterness, Umami along with smell don't actually seem to come into play when determining whether a unknown plant is edible. If I recall you are supposed to try a little of the plant and if after 24 hours you don't get sick, try a bigger portion (again from memory--I'm sure mother nature would kick my butt if I was in a survival situation, lol).
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    Gerhard Adam's picture
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    I agree, and I'm sure there are numerous such notions regarding how one can evaluate food safety.  However, I see you agree with the essence of my point which is that regardless of the particular taste, it doesn't appear that there is any evolutionary basis for presuming that the specific taste plays a role in determining what foods are edible or good for you.
    Mundus vult decipi
    KRA5H's picture
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    "it doesn't appear that there is any evolutionary basis for presuming that the specific taste plays a role in determining what foods are edible or good for you."

    Yup, we agree. There's no "evolutionary basis for presuming that the specific taste plays a role in determining what foods are edible or good for you."





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    scubapro25 (not verified)
    scubapro25's picture
    Hi, Gerhard:

    You said:


    (1)  Evolutionary Psychology presumes that male behavior is based on the notion that there is a minimal investment in reproduction and therefore they will tend to mate with as many females as possible, of course, real world experience indicates otherwise........



    I'm not meaning to be flip in my comment here, but why did you say 'of course, real world experience indicates otherwise" ? 


    What 'real world experience' are you referring to? 


    Not being a   sociologist, I've never done a proper scientific, sociological survey on the matter, but the last time I checked, to use a more generous term 'non-monogamous' males were running rampant in many cultures, with some cultures, such as French and Hispanic to name only two, presuppose married men having mistresses--to say nothing of the unfaithful single male of many cultures [I realize we are not exempt]. 


    So where are all these paragons of monogamy you seem to be referring to here? 







    Gerhard Adam's picture
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    Well, the evidence is clearly present when one considers that the majority of men will propose and get married [in most cultures].   Most evidence suggests that humans are serially monogamous, but nevertheless they tend to be monogamous.  [NOTE: To clarify, most men do not favor marrying promiscuous females with whom they wish to reproduce].

    While you mention "non-monogamous" males as running rampant, the problem with that argument is that it occurs with nearly as much frequency in females.  That is a strong argument against an evolutionary component.  Although men tend to cheat more, female infidelity is increasing as women gain more financial and social independence.  Again, this raises the question of opportunity and context rather than evolution.

    Even using your example of having a mistress is interesting, because the mere fact that we have a word like "mistress" still suggests a more long-term relationship rather than just blatant promiscuity.  In fact, this division also illustrates my point below, which is that one woman is there for reproduction, while the other is for sexual pleasure.  The point is made much more clear when observing a truly promiscuous species versus the relatively constrained behavior of humans.

    It is estimated that 2-3% of children are the product of infidelity, which clearly is derived from females.  In fact, this is one of the fundamental questions raised [and contradicted in evolutionary psychology discussions] while asserting that males are promiscuous, they correspondingly inject the problem of paternal uncertainty.  It should be obvious that males cannot be promiscuous without cooperating females, since the sex ratios are nearly equal.
    On average, males have to have as many mates as females, says Marlene Zuk, an evolutionary biologist at the University of California at Riverside.
    http://www.livescience.com/32684-why-are-most-animals-promiscuous.html

    In any case, all of these statistics and points miss the primary issue.  They are all about sex and not reproduction.  This is such a huge difference, that virtually everything we have ever studied about humans is suspect, in this regard, if we wish to invoke evolution.

    I can think of few instances of where the objective in promiscuous behavior is to increase the number of children.  In fact, if you were to examine most cultures, I think you would find little evidence to support males "rampaging" through society, fathering offspring.

    This is the primary argument against an evolutionary component, since without reproduction there is no means by which such behavioral traits [presuming they are genetic] would be passed along.

    Instead, I would argue that somewhere in our evolutionary past, sex and reproduction became separated in our behavioral traits.  The focus appears to have shifted to sexual pleasure as being a driving force in our biology, rather than the more general "heat" cycles that typically  announced fertility. 

    So while there are plenty of species that one could call promiscuous, invariably there is no problem in announcing fertility and then maximizing mating opportunities.  Yet that isn't what we observe in humans.  Instead we see more focus on the sexual, rather than reproductive, aspects and a much more influential trait towards longer term pair bonding, which I suggest is due to our obsession with sexual pleasure.

    I've been quite long-winded enough, but my point is simply that you will find little evidence for male promiscuity for the purposes of reproduction, which is what evolution would depend on.  Instead, we find that there is a tendency to be serially monogamous, and that such behaviors tend to be more evenly divided between the sexes, primarily motivated by the culture and opportunity rather than evolution.

    http://www.truthaboutdeception.com/cheating-and-infidelity/stats-about-infidelity.html
    Mundus vult decipi
    scubapro25 (not verified)
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    OK, well, fair enough then. Either you didn't specify that was what you meant, or you did and I missed it. Most likely that latter.
    You are correct: examples of promiscuity for the purposes of reproduction are rare and in fact, when they do occur, as I'm sure you know, are accidental due to the failure to use proper contraception. 

    And, I also agree with you that somewhere along the line with Homo sapiens, sexual pleasure and reproduction did fork off, hence the cultural predisposition towards having mistresses, who are clearly not for reproductive purposes--that's what the wife is for.

    I might also add, not that it's necessarily connected with our discussion, but only because as diver, I'm in the ocean a lot and happened to know otherwise useless factoids like this, but Homo sapiens is not the only species that has sex for pleasure: dolphins and some species of Beluga whale are well-known to have sex for pleasure--there are even cases of same sex sexual activity, what we might call homosexual activity with cetaceans, and even some species of monkeys. There is even one case I'm aware of that was documented on video, of a dolphin sexually harassing a diver underwater, sporting a huge erection. So, what would that be? Inter-species homosexuality (the diver in question was a male also)? Oh, god, who knows. But, again, I realize I have digressed from the main topic.

    However, perhaps no so much simply because it does show that sex for pleasure is not limited to our species, so your point is well taken.

    Gerhard Adam's picture
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    I think you bring up some good points, because the issue of a trait for sexual pleasure provides some clear answers to things which are always treated as ambiguous from an evolutionary perspective.

    For example, your point about interspecies homosexuality, or virtually any kind of sexual behavior is well explained by considering the role of the brain and sexual pleasure rather than trying to find some evolutionary reproductive explanation.

    In my view [just speculation], sexual pleasure provided a means of ensuring that no creature with higher cognitive abilities could "game" the system.  In other words, fertility periods are essentially hidden and by seeking the pleasure of sex, then it was a means of ensuring a relatively consistent means of promoting sexual interest and ensuring maximum reproductive coverage.

    However, a consequence of that is that sexual desire is self-contained and can still manifest itself even without an appropriate reproductive target.  Everything from self-gratification, to the faux homosexuality of prison populations, to all manner of different sexual orientations.  Since they all originate in the mind, there is no basis for asserting that they have a direct evolutionary component that can be traced back to reproductive advantage [i.e. fitness].

    You're also right that I probably wasn't as specific as I should have been [merely wishing to kick start the forums].  In particular there was a recent article [and some papers] published that touched on this topic as well as a few others related to social monogamy.

    However, as you noted, my objection to the explanations from evolutionary psychology are because invariably these results are produced by taking surveys of college students, so because males seem more interested in many females, the conclusion becomes self-affirming.  Yet, this occurs precisely because the researchers keep confusing sexual pleasure with reproduction.
    Mundus vult decipi
    scubapro25 (not verified)
    scubapro25's picture
    Good points, all.
    Actually, since we're on the subject and you appear to better versed in recently EP literature than me, what *is* the EP explanation for homosexual behavior--if there is one?

    It's always struck me as odd--from an evolutionary perspective--that *any* trait that does *not* lead to offspring (at all), would have been weaned out long ago. Don't get me wrong: I'm not anti-gay, it's just that from an evolutionary perspective, homosexual sex is a dead end--literally nothing can be passed on--since no fertilization take place--obviously. Even 'desirable' traits obviously cannot be transmitted.

    You could say that masturbation does not lead to offspring either, which would be true, but there is nothing inherent in masturbation that precludes *later* not having sex with a fertile female--and, in fact could be construed as 'practice,' as well as letting off hormonal 'steam' so to speak. 

    But, nothing in homosexual sex could possible transmit genetic traits.

    So, is there an EP explanation for it? 

    Gerhard Adam's picture
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    One issue that needs to be dealt with is the notion that every trait must necessarily serve an evolutionary purpose.  As a result, we often find that there are numerous convoluted explanations to account for it, rather than simply acknowledging that traits don't need to be specifically selected to be maintained at some level within a population.

    One point that evolutionary psychology uses is the idea of "kin selection" where the argument goes that a "gay gene" would be propagated because these males tend to invest in their relatives [i.e. kin] and therefore ensure their survival more readily.  This is based on the idea that being gay is heritable and therefore requires some genetic component be transmitted.

    Again, I think this explanation attaches too much importance to genetics.  Unless these gay males involvement was instrumental in ensuring the survival of their relatives, then even if they did nothing a "gay gene" would continue to be present in the population, so I'm not convinced that this is that important an explanation.

    In addition, the concept of "kin selection" is often abused by being directly linked to genetic heritage when this is not necessarily how kin are viewed in other parts of the world, so the concept of supporting relatives has a wide range of interpretations depending on culture.  It is primarily from a European perspective that we have the notion of "blood" relations.

    If you look at the links at the bottom, you'll find all kinds of explanations and rationalizations, but the net of it is, that there doesn't have to be any particular benefit or cost to being gay from an evolutionary perspective.  The gene will persist all by itself, because of our primary purpose being social cohesion.  This view is also supported in highly social animals, where it is clear that many of the members don't reproduce.  In the eusocial insects this has gone to the extreme of turning reproductive "rights" over to a queen.  So, clearly there can be large populations and sophisticated social organizations without the need for every member to reproduce.  Consequently that is a strong argument against why it would be necessary for gay individuals to reproduce.

    The problem with most of the explanations is that they assume that humans are fundamentally isolated and compete with each other for reproductive rights and a presence in future generations.  In reality there is little real competition and the primary purpose of humans is to promote greater and greater social cohesion.  In other words, we live more like ants than grizzly bears [so I wouldn't expect to see many homosexual bears].

    http://www.psychologytoday.com/blog/sex-dawn/201002/explaining-the-gay-s...
    http://www.sciencedaily.com/releases/2010/02/100204144551.htm
    http://www.psychologytoday.com/blog/natural-history-the-modern-mind/2009...

    Another good book to read on the subject is:
    Social Bonding and Nurture Kinship by Maximilian Holland

    This book discusses all the issues from an anthropological, as well as biological point of view. 
    Mundus vult decipi
    Bonny Bonobo alias Brat's picture
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    According to this website  'over 1,500 different animal species practice homosexuality'.
    '9 out of 10 giraffe pairings occur between males, male bottlenose dolphins go through periods of being exclusively homosexual, female macaques form intense bonds with each other and are serially monogamous,&almost a quarter of black swan families are parented by homosexual couples.

    'There are even pairs of penguins that are gay at New York City's Central Park Zoo, the New York Aquarium, Germany's Bremerhaven Zoo and a pair of gay flamingos at the Wildfowl&Wetlands Trust in Gloucestershire, England.'


    Wiki also has an article called 'List of animals displaying homosexual behavior' :-

    'For these animals, there is documented evidence of homosexual behavior of one or more of the following kinds: sex, courtship, affection, pair bonding, or parenting, as noted in researcher and author Bruce Bagemihl's 1999 book Biological Exuberance: Animal Homosexuality and Natural Diversity.'

    And guess what? The Brown Bear is on the list! I know that big hairy gay guys are often called 'bears' in the gay community but I didn't realise that brown bears could also be gay, as can koalas! Maybe gays call little, hairy, gay, Australian guys koalas?









    My article about researchers identifying a potential blue green algae cause & L-Serine treatment for Lou Gehrig's ALS, MND, Parkinsons & Alzheimers is at http://www.science20.com/forums/medicine
    Gerhard Adam's picture
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    According to this website  'over 1,500 different animal species practice homosexuality'.
    Hmmm ... so how long does it take them to practice before they get good at it?

    Obviously someone is confusing behavior with orientation.

    Mundus vult decipi
    Bonny Bonobo alias Brat's picture
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    Interesting how many animals can practice and exhibit homosexual behaviour though, isn't it? There are also a lot of fish and insects on that list.

    I once went to a gay club in London, with a girlfriend, by mistake. It used to be a pub in Clapham Junction that had bands for free on most nights. By the time we had walked up to the bar we realised things had changed a lot. Anyway, we ended up staying and having a great time. It was mainly gay men and transsexual men dressed as women, we were the only heterosexual women there and maybe the only women, so we felt very safe. 

    I was amazed at how ungay many of the men looked, I would never have guessed that most of them were gay though many of them were very handsome. Two guys who were a couple, were very friendly to us, bought us drinks and danced with us all night. One was a lawyer the other a doctor, both were in their thirties and had not 'come out' as it would have been bad for them professionally. They said that when they were about 40 years old, no one would want them anymore in the gay community, so they would probably get married to a heterosexual woman and have kids, like many other gays before them. 

    They walked us to our car and then amazed us by asking for goodnight kisses, maybe they were on the look out for future wives or needed some practice or they were just proving a point :)
    My article about researchers identifying a potential blue green algae cause & L-Serine treatment for Lou Gehrig's ALS, MND, Parkinsons & Alzheimers is at http://www.science20.com/forums/medicine
    scubapro25 (not verified)
    scubapro25's picture
    Excellent, Gerhard: thanks for your edifying reply--I clearly can learn a lot from your posts, so I will make a point of following them in the future. I shall also check out the links you gave. 
    EP is a subject that has fascinated me over the years, but the ocean has take a lot of my time lately, so I need to restart the process of self-education on the subject again. 


    Gerhard Adam's picture
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    I think we make too big a fuss over it.  It's obviously one aspect of a spectrum of sexual behaviors and orientations.  Basically, it doesn't really mean very much [obviously it means a lot to people that are denied rights] compared to the amount of attention we give to it.
    Mundus vult decipi
    Bonny Bonobo alias Brat's picture
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    I think we make too big a fuss over it.  It's obviously one aspect of a spectrum of sexual behaviors and orientations.  Basically, it doesn't really mean very much [obviously it means a lot to people that are denied rights] compared to the amount of attention we give to it.

    It might mean a lot to the women that the gay guys marry when they are in their forties though!
    I don't understand how the subject in the forums is supposed to work? When we reply to a post, why doesn't it take the default subject of the post we are replying to?
    My article about researchers identifying a potential blue green algae cause & L-Serine treatment for Lou Gehrig's ALS, MND, Parkinsons & Alzheimers is at http://www.science20.com/forums/medicine
    scubapro25 (not verified)
    scubapro25's picture
    Helen:
    Forgive me for jumping in here, but I found myself agreeing with you on two points: the first is the subject line above (ya think?) and the second is, I too, was wondering why I kept having to retype the subject line in each time myself. Perhaps someone will have an explanation for that. Most forums, the software automatically adds the subject line you were replying to. 

    Back to the subject line, as a straight male who has had and has gay friends, I still find myself ignorant about a lot. I was asking Gerhard how gay 'traits' can be passed on, when gays themselves cannot, obviously reproduce outside of having heterosexual sex (see his excellent answer to my question above) and, the other evolutionary intriguing phenomenon is bi-sexuality. Is that just called 'covering your bets'? I don't mean to be flip when I say that--in fact, it may be the 'only' way that traits associated with being gay *can* be passed on. 

    And, don't forget, back in the 'bad old days' before gays 'came out' of the closet, many *did* in fact, marry straight women and have children with them, long before the wife ever found out--but, they say women 'always' know--or, at least suspect, when a husband or mate is gay--the finding of gay porn in the the back of the closet  not withstanding. Well, obviously, not being a woman, I am not qualified to address that issue. Perhaps you are. 
    Bonny Bonobo alias Brat's picture
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    Thanks for replying Michael. The guys we met were a doctor and a lawyer, there are many professions in which being openly gay would be quite a significant career disadvantage. These very intelligent and well-educated gay guys told us that one in five men are gay and many of them will marry in their forties and have children. If they are right then that explains how the genes for homosexuality are passed on. Of the one in five men who are gay, many will not ever openly admit this or even practice homosexuality (yes practice Gerhard :) and a significant percentage will suicide in their late teens and early twenties because they are unable to cope with their own homosexuality and the stigma.

    So as far as the 'bad old days' before gays 'came out' is concerned, there are still millions of women marrying gay men in their forties and having children with them. Those days are not over. Many of these women enter these relationships thinking that love will be enough, I saw a documentary in which the wives were being very long suffering with their gay husbands, I guess that it is either that or divorce? As far as women knowing when a guy is gay, I wouldn't know, I've been with my husband for over 30 years and he is definitely not gay. 

    I'm a counsellor and quite often my female clients are wanting to have boob implants, my advice to them is to not do this specifically to attract men, as from my experience with the many women I know who have boob implants or already have very large breasts, this tends to attract men with very low sex drives, who need a lot of stimulation to get turned on. Better to have small boobs and attract highly sexed heterosexual guys in my opinion! Not sure where homosexual guys would fit into the equation, though, maybe they would prefer small breasts on the women they eventually marry? It would be an interesting psychological study to do.

    My article about researchers identifying a potential blue green algae cause & L-Serine treatment for Lou Gehrig's ALS, MND, Parkinsons & Alzheimers is at http://www.science20.com/forums/medicine
    Gerhard Adam's picture
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    Helen, there are a couple of problems with your explanation.  Your premise is based on the assumption that being gay is directly inherited, such that gay men would produce other gay men.  There is no direct evidence that such a situation is exists.

    Similarly, there are numerous situations of where straight men produce gay offspring, so again, there is no direct inherited evidence.

    The second problem is that you're presuming that a "gay" trait would be passed on by the father, but that also hasn't been established, since it could quite readily be passed on by the mother [which would clearly account for its persistence in the population].

    Thirdly, without evidence for an actual "gay" gene, one can't exclude possible epigenetic effects that give rise to such a trait.

    However, as stated previously, there is no need for gay men to directly reproduce anyway.  Any siblings would be just as prone to carry such a gene, and therefore their reproduction would be sufficient to ensure such a gene's persistence in the population.  Also, as stated previously, unless a gay sibling's contribution was instrumental in ensuring the survival of such siblings, then it isn't even necessary for a gay individual to contribute to the family to ensure the perpetuation of such a trait.

    So, in a nutshell, there's not any evidence that homosexuality has any evolutionary component at all.   Beyond that fact that it appears to be genetic, there is no indication that it is a selectable trait, nor that there is a clear inheritance pattern.

    In fact, if one wanted to engage in purely speculative terms then, if we consider the stereotype of gay men as being more creative/artistic, then one might form a hypothesis that "gayness" was a function of brain development and not directly genetic as a particular trait.  Since we also considered that humans split between the sexual pleasure [i.e. cognitive] versus reproductive [physical] aspects of their evolution, then may be quite reasonable to argue that differences in brain development that result in such higher creativity may also be responsible for influencing the sexual orientation of the individual.

    Now I want to be clear, that I'm only using a gay stereotype and that this is purely SPECULATIVE.  However, I'm stating it simply to demonstrate that there may be significantly more factors at work than merely a gene's expression of a particular trait.
    Mundus vult decipi
    scubapro25 (not verified)
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    I wish there was a 'Like' button here for all the great comments..... :)
    Gerhard Adam's picture
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    Thanks Mike, it's appreciated. :)
    Mundus vult decipi
    Bonny Bonobo alias Brat's picture
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    "Helen, there are a couple of problems with your explanation.  Your premise is based on the assumption that being gay is directly inherited, such that gay men would produce other gay men.  There is no direct evidence that such a situation is exists."
    I never said that, I just said that there is plenty of evidence that gay men can and do reproduce heterosexually.
    "Similarly, there are numerous situations of where straight men produce gay offspring, so again, there is no direct inherited evidence."
    Who said there was? Not me.
    "The second problem is that you're presuming that a "gay" trait would be passed on by the father, but that also hasn't been established, since it could quite readily be passed on by the mother [which would clearly account for its persistence in the population]."
    I'm not presuming that at all. I think that gay mothers can also reproduce heterosexually.
    "Thirdly, without evidence for an actual "gay" gene, one can't exclude possible epigenetic effects that give rise to such a trait."
    Who said I was? There is plenty of evidence now that in utero hormone levels have a profound effect upon the sexual preferences of the baby.
    "However, as stated previously, there is no need for gay men to directly reproduce anyway.  Any siblings would be just as prone to carry such a gene, and therefore their reproduction would be sufficient to ensure such a gene's persistence in the population.  Also, as stated previously, unless a gay sibling's contribution was instrumental in ensuring the survival of such siblings, then it isn't even necessary for a gay individual to contribute to the family to ensure the perpetuation of such a trait."
    Totally agree.
    "So, in a nutshell, there's not any evidence that homosexuality has any evolutionary component at all.   Beyond that fact that it appears to be genetic, there is no indication that it is a selectable trait, nor that there is a clear inheritance pattern."
    What nutshell? Of course there has to be an evolutionary component to every trait of a living being.
    "In fact, if one wanted to engage in purely speculative terms then, if we consider the stereotype of gay men as being more creative/artistic, then one might form a hypothesis that "gayness" was a function of brain development and not directly genetic as a particular trait.  Since we also considered that humans split between the sexual pleasure [i.e. cognitive] versus reproductive [physical] aspects of their evolution, then may be quite reasonable to argue that differences in brain development that result in such higher creativity may also be responsible for influencing the sexual orientation of the individual."
    I'm not engaging in purely speculative terms, I'm saying there is plenty of evidence that homosexuals reproduce heterosexually and that there may well be genes and environmental factors involved in the continued evolution of homosexuality.
    "Now I want to be clear, that I'm only using a gay stereotype and that this is purely SPECULATIVE.  However, I'm stating it simply to demonstrate that there may be significantly more factors at work than merely a gene's expression of a particular trait."
    I totally agree, there are obviously many more factors at work than just a gene's expression but to say that homosexual men don't reproduce heterosexually is obviously a very wrong assumption that a lot of people make. Glad we've cleared that up :)
    My article about researchers identifying a potential blue green algae cause & L-Serine treatment for Lou Gehrig's ALS, MND, Parkinsons & Alzheimers is at http://www.science20.com/forums/medicine
    Gerhard Adam's picture
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    I think that gay mothers can also reproduce heterosexually.
    You're attaching to much significance to one of the parent's being gay and I'm saying that has nothing to do with anything.
    Of course there has to be an evolutionary component to every trait of a living being.
    No there doesn't.  You're taking the position of "adaptionism" and there's no requirement that any given trait be selectable or adaptive.  In fact, some traits that may be adaptive may be coincident with other traits that aren't.  These latter are effectively "free riders" that contribute nothing but may persist anyway.

    An example of such a trait may be lactose intolerance [in modern times].  While it may convey an advantage in specific environments, it is not really a selectable trait in the absence of such environmental pressures.  Yet, it may persist in the population.  The mere fact that some portion of the population is lactose-tolerant, suggests that this trait was already present [to some degree] in the population and when those individuals adopted milk for nutrition, the trait was selected.

    However, milk is not a sufficiently strong requirement as to exert a fitness result, so consequently it is a trait that may or may not be present because there is no strong selection criteria associated with it.  The same could be said of numerous phenotypic traits that humans have [i.e. hair color, eye color, etc.].  If there is no fitness advantage it is not subject to selection and yet can persist in a portion of the population indefinitely.  Not being selectable also means it isn't likely to be "selected out".
    I'm saying there is plenty of evidence that homosexuals reproduce heterosexually ...
    My point is that there is no such requirement.
    Mundus vult decipi
    Bonny Bonobo alias Brat's picture
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    "I think that gay mothers can also reproduce heterosexually."
    "You're attaching to much significance to one of the parent's being gay and I'm saying that has nothing to do with anything."
    Of course it has something to do with the evolution of human behaviour. If gay men and women didn't reproduce heterosexually, then the likelihood is that there would probably be less gay people born in the world. 

    It may simply be that whatever makes someone gay, also has a significant genetic effect upon the in utero hormonal conditions that have been linked with the babies subsequent homosexuality. Maybe some babies are genetically more susceptible to in utero hormonal fluctuations or maybe the gay mothers themselves (whether they are in or out of the closet) are genetically more susceptible to creating the hormonal in utero fluctuations that have been linked with homosexuality? The number of factors involved both from nurture and nature are always very difficult to pin down, there might even be social factors, dietary factors, age factors, health factors, however you cannot remove the high possibility of genetic factors from homosexual parents too.
    "Of course there has to be an evolutionary component to every trait of a living being."
    "No there doesn't.  You're taking the position of "adaptionism" and there's no requirement that any given trait be selectable or adaptive.  In fact, some traits that may be adaptive may be coincident with other traits that aren't.  These latter are effectively "free riders" that contribute nothing but may persist anyway."
    I'm not saying that every trait is selectable or adaptive but I am saying that every genetic trait has evolved. If it hadn't then it wouldn't and couldn't exist. I don't think that the homosexual genes are necessarily selectable or adaptive, they have evolved to just exist and they keep reproducing like many other genes that also have evolved to just exist and keep evolving and existing, probably more by chance than anything.
    "An example of such a trait may be lactose intolerance [in modern times].  While it may convey an advantage in specific environments, it is not really a selectable trait in the absence of such environmental pressures.  Yet, it may persist in the population.  The mere fact that some portion of the population is lactose-tolerant, suggests that this trait was already present [to some degree] in the population and when those individuals adopted milk for nutrition, the trait was selected."
    "However, milk is not a sufficiently strong requirement as to exert a fitness result, so consequently it is a trait that may or may not be present because there is no strong selection criteria associated with it.  The same could be said of numerous phenotypic traits that humans have [i.e. hair color, eye color, etc.].  If there is no fitness advantage it is not subject to selection and yet can persist in a portion of the population indefinitely.  Not being selectable also means it isn't likely to be "selected out"."
    Yes I agree. Homosexuality is probably like eye colour or hair colour, it doesn't give any fitness advantage and it is not subject to selection, so it will just persist and continue to evolve within the population indefinitely.
    "I'm saying there is plenty of evidence that homosexuals reproduce heterosexually ..."
    "My point is that there is no such requirement."
    Well if people with brown eyes or brown hair stopped reproducing there would eventually be less people with brown hair and eyes in the population, I think the same applies to homosexual men and women, if they stopped reproducing heterosexually there would eventually be less homosexual people in the population. But its not going to happen anytime soon :)
    My article about researchers identifying a potential blue green algae cause & L-Serine treatment for Lou Gehrig's ALS, MND, Parkinsons & Alzheimers is at http://www.science20.com/forums/medicine
    Gerhard Adam's picture
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    I think you're using the word "evolve" in a strange way. 

    In any case, your statement:
    Well if people with brown eyes or brown hair stopped reproducing there would eventually be less people with brown hair and eyes in the population...
    Yes, since you have now redefined it to be a selectable trait with some environmental element that would select against brown coloring.  Eventually such a trait could disappear but it doesn't need to, it might just become increasingly rare.

    It's like the example of the peppered moth, where the dark variety dominated in polluted areas, whereas the light variety dominated in pollution-free areas.  The point is that this characteristic indicates that the trait never fully disappeared, although as the environment changed certain varieties would come to dominate the population.  Yet, this interpretation is incomplete.
    http://www.millerandlevine.com/km/evol/Moths/moths.html

    In other words, for a diploid species, the genotype would have to be homozygous to completely eliminate a trait, which doesn't seem likely in this case.  In other words, if there is a "gay gene", then it would be just as readily propagated by "straight" individuals since it has no impact on their fitness, the gene would persist within the population.  Since there is nothing that would render the gene selectable, it can't be selected out.  In other words, there is neither advantage nor disadvantage to the carrier of this gene.

    Given the large human population, it is unlikely that a few individuals that don't reproduce would be enough to affect the distribution of a genotype for these traits [homosexual or heterosexual].  In fact, given the low or non-existent fitness cost associated with this [in modern society with its large population],  an increase of this trait could occur without negatively impacting fitness in humans.

    Mundus vult decipi
    Bonny Bonobo alias Brat's picture
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    OK, so what's the point in all of this? You kicked this forum off by saying :-
    "Just to kick things off, I'd be curious to know what people's thoughts are on the role of biological evolution on human behavior.
    There are so many quaint "just so" stories floating around, there's got to be someone willing to take this subject seriously.
    For starters, two questions come to mind."
    (1)  Evolutionary Psychology presumes that male behavior is based on the notion that there is a minimal investment in reproduction and therefore they will tend to mate with as many females as possible.  Of course, real world experience indicates otherwise, so why should this view be so prevalent?
    So why are we talking about homosexual behaviour and its possible genetic evolution? Maybe its valid to point out that if the majority of the one in five men who are homosexual, then go on to father children in their forties, maybe their average reproduction rate is as high as the average heterosexual man and is that relevant at all? 


    BTW, somewhere I remember you said something about 2 to 3% of offspring are conceived through infidelity by the woman. Well I can't be bothered to find it now but I watched a documentary several years ago that quoted a much higher figure of between 20 and 30% of children in partnerships being conceived through infidelity, so where did you get that 2 to 3% from?
    My article about researchers identifying a potential blue green algae cause & L-Serine treatment for Lou Gehrig's ALS, MND, Parkinsons & Alzheimers is at http://www.science20.com/forums/medicine
    Gerhard Adam's picture
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    So, you didn't read any of the earlier links I provided :)
    So why are we talking about homosexual behaviour and its possible genetic evolution?
    Don't know ... you brought it up.
    Mundus vult decipi
    Bonny Bonobo alias Brat's picture
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    Actually Michael Bear did and now maybe he has gone into hibernation :)
    My article about researchers identifying a potential blue green algae cause & L-Serine treatment for Lou Gehrig's ALS, MND, Parkinsons & Alzheimers is at http://www.science20.com/forums/medicine
    scubapro25 (not verified)
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    Helen:
    No, I didn't actually to into hibernation (even though my last name *is* Bear).......I just went away for a day or two and when I came back, I noticed that the discussion of genetic 'traits' and characteristics' for homosexuality (and lactose intolerance) has gone waaay over my head and now I feel intimidated by you two smarties. :)

    Seriously, did *I* really bring it up? I guess I did.....mea maxima culpa! 
    Bonny Bonobo alias Brat's picture
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    "I just went away for a day or two and when I came back, I noticed that the discussion of genetic 'traits' and characteristics' for homosexuality (and lactose intolerance) has gone waaay over my head and now I feel intimidated by you two smarties. :)"
    Gosh, that's not good Michael, you must never feel intimidated by Gerhard and especially me, that's the last thing either of us would ever want! It must be great having the surname Bear, I would love to be called Helen Bear, though I imagine there are no end of comments about your name. What did they call you at school and college?

    My article about researchers identifying a potential blue green algae cause & L-Serine treatment for Lou Gehrig's ALS, MND, Parkinsons & Alzheimers is at http://www.science20.com/forums/medicine
    scubapro25 (not verified)
    scubapro25's picture
    Helen:
    Well, I was sort of joking--I mean, I just admire the way you two go at 'hammer and tongs' like that......and, Gerhard is no pushover, either, so you hold your own well also. 

    They didn't really call me anything weird in college--now, everyone just calls me Mikey--which is sort of funny, because I'm over 50. Go figure......anyway, don't worry, I'm not quitting.....I still enjoy talking with you and Gerhard. :)
    KRA5H's picture
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    Here's a study that might shed some light on the subject: http://www.pnas.org/content/103/28/10531.full<p>
    It's kind of old (2006) and I don't know if there have been any followup studies.
    "This page intentionally left blank." --Gödel
    Bonny Bonobo alias Brat's picture
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    That's a really interesting link and study Steve, that demonstrates the much higher incidence of male babies becoming gay, if their mothers had already given birth to sons and the likelihood of being gay increasing with the number of older brothers the male baby has :-
    'Maternal immunization hypothesis. When a mother is carrying her first son, the placental barrier protects each from exposure to the other’s proteins. But inevitable mixing of blood upon delivery will expose the mother for the first time to male-specific proteins (blue triangles), including those encoded on the Y chromosome. If her immune system produces antibodies to these proteins, then the placenta may actively transport those antibodies (indeed, all IgGs) to subsequent offspring in utero, potentially affecting development of later-born sons, but not later-born daughters.'
    I didn't know that the same doesn't apply to male, left handed babies though. It doesn't matter how many older brothers they have, if they are left handed it doesn't increase their likelihood of subsequently being gay, isn't that amazing?

    'Most recently, Blanchard et al. (15) collated several data sets and found another surprise: older brothers increase the probability of a boy becoming gay only if that boy is right-handed. Among left-handed men, there’s no difference in the incidence of homosexuality no matter how many brothers they have. What’s curious about this finding is that, by itself, left-handedness makes males and females slightly more likely to be gay (16). So left-handedness makes males slightly more likely to be gay but also negates the effects of older brothers on orientation.'
    My article about researchers identifying a potential blue green algae cause & L-Serine treatment for Lou Gehrig's ALS, MND, Parkinsons & Alzheimers is at http://www.science20.com/forums/medicine
    Gerhard Adam's picture
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    I didn't know that the same doesn't apply to male, left handed babies though. It doesn't matter how many older brothers they have, if they are left handed it doesn't increase their likelihood of subsequently being gay, isn't that amazing?
    I suspect it may have something to do with the fact that most gay rights issues are considered liberal or "left-wing" agendas, so if a baby is born left-handed, then it may already be as far left as it needs to be to form its political orientation.  :)

    Mundus vult decipi
    KRA5H's picture
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    Here's the Lactase persistence article: http://www.nature.com/ejhg/journal/v13/n3/full/5201297a.html
    "This page intentionally left blank." --Gödel
    Gerhard Adam's picture
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    It is also important to keep the microbial element in mind.  In other words, the ability to process milk may not be purely genetic.  While there may certainly be a genetic component to it, it could also be adaptively accelerated in those that pick up the proper gut bacteria to assist in its digestion.
    http://genetics.thetech.org/ask/ask135
    Mundus vult decipi

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