Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Will evolution eradicate homosexuality?

  1. Sep 26, 2011 #1
    I am an amateur studying physics on my own accord purely to satisfy my own curiosity and new to the forum , so please be gentle if i am stating something blatantly obvious or that has been discussed already.

    I was not studying this topic but had discussions with someone about DNA and then separately about homosexuality and homosexuality in history.

    Basically they questioned how many people were homosexual in the past.

    Well i thought that purely from a scientific and evolution point of view being homosexual is a genetic flaw , i mean our existence is down to humans reproducing and obviously if people of the same sex are together they are not reproducing.
    Evolution and natural selection tends to iron out a lot of flaws so i thought surely if flaws are generally being ironed out like this then it must have been more flawed in the past (a higher percentile of people could have been homosexual?).

    Then i thought about the social side of this and there are many points in the past where homosexuality was an outright taboo or illegal and is still illegal in many countries today.
    As a result people must have been feeling forced into trying to "act normal" and have partners of the opposite sex and have offspring which would be passing these "flawed" genes on to their offspring.

    As i said i understand homosexuality is still illegal in many countries today but it is vastly more acceptable on a global scale than it was say 50 years ago , You would expect if current trends continue that homosexuality is only going to be accepted more and more and people will feel free to be open about this and cohabit with members of the same sex instead of trying to "act normal" and have an opposite sex partner and produce offspring.

    In this scenario surely less homosexual people will have offspring and as a result these genes will decrease exponentially. I understand there are other ways for people to have offspring and IVF etc and as a result people in same sex relationships could still have offspring but obviously this is much harder to do than just having intercourse so surely a fewer percentage of offspring would have these genes?

    So basically im asking Will evolution eradicate homosexuality ?
    Will society openly accepting homosexuality mean there is no need for people in this situation to "live a lie" and basically mean they reproduce less and these genes start to disappear ?

    P.S. I'm neither homosexual or homophobic , i just found the subject interesting from an evolutionary standpoint.
     
  2. jcsd
  3. Sep 26, 2011 #2

    Ryan_m_b

    User Avatar

    Staff: Mentor

    Whilst we don't know the exact cause of sexuality we are certain that it isn't as simple as a gay gene. It is far more likely that homosexuality (along with every other sexual variant) is a by-product of our ability to possess a sexuality. Therefore it will not be "evolved out" unless our capacity to have a sexuality disappears.
     
  4. Sep 26, 2011 #3
    Thanks for the reply Ryan , I did not understand this and will go read up on some of this. Am i wrong is saying though that everyone has the ability to possess sexualities but only some people will be homosexual and therefor their genetic makeup could be a factor still in determining this?
     
  5. Sep 26, 2011 #4

    Ryan_m_b

    User Avatar

    Staff: Mentor

    Not everyone, some people are born asexual. The reasons for variation in sexuality are largely unknown but I doubt it is genetic as there are many cases of monozygotic twins that have different sexualities. There has been a lot of study on this topic ranging from examining the epigenetics (I.e. a list of which genes are on and which are off) of both the person and their mother, various factors of development such as hormone levels and social/psychological reasons. For a good summary I would advise you read this http://en.wikipedia.org/wiki/Biology_and_sexual_orientation" [Broken].
     
    Last edited by a moderator: May 5, 2017
  6. Sep 26, 2011 #5
    Exactly, it is not as simple as that. Phenotypes often have very complex relationships with their genotypes. A single gene may be responsible for multiple phenotypes and a single phenotype is almost never the result of a single gene. And when it comes to behavourial patterns, things can get complicated, since developing a one to one relation between behaviour and genes is pretty difficult. Homosexuality as a trait could be a byproduct of the various complex social interactions that our brain is made to cope with. It could also be influenced by epigenetics.
     
  7. Sep 26, 2011 #6
    I'd say that Hamilton's Rule applies here, for the same reasons that altruism remains a behavioral trait in humans. Should an organism reduce its own reproductive fitness, it nevertheless would pass on its genes (since relatives often share the same genes) if the benefit towards their immediate kin and increase in overall fitness outweighs the loss of individual fitness.

    At least this explains the behavior of some animals (e.g., the evolution of worker bees that do not reproduce). Humans tend to have complex confounding cultural aspects however.
     
  8. Sep 26, 2011 #7

    Evo

    User Avatar

    Staff: Mentor

    I think the OP doesn't quite understand how natural selection works, as well as not understanding that an individual's sexual preference is too random in the human population to be selected against.

    Also, from a historical perspective, homosexuality has gone in and out of acceptance socially. For example, it was widely accepted among the Celts.
     
  9. Sep 26, 2011 #8
    I probably could do with reading more into it and will do , as i said i really am an amateur who has/is developed an interest in science so i will have a lot of gaps.

    Thanks Ryan i will read this.
     
    Last edited by a moderator: May 5, 2017
  10. Sep 26, 2011 #9

    Evo

    User Avatar

    Staff: Mentor

    Try this video, so simple, explains natural selection.

     
    Last edited by a moderator: Sep 25, 2014
  11. Sep 26, 2011 #10
    Thanks Evo :)
     
  12. Sep 26, 2011 #11

    Evo

    User Avatar

    Staff: Mentor

    Posts have been deleted that were not scientifically accurate and responses to those posts.
     
  13. Sep 26, 2011 #12
    I agree that something like a gay gene doesn't exist, and probably homosexuality is a byproduct of the complex human geno- and phenotype.

    Still, if you look at it from a Darwinistic perspective, there's one possible thing overlooked in the question. No doubt, homosexuality is bad for the survival of the DNA of an individual. But why couldn't a limited degree of homosexuality in a society be good for the survival of that society?
     
  14. Sep 26, 2011 #13

    Ryan_m_b

    User Avatar

    Staff: Mentor

    I'd like to echo Evo's post and ask everyone to stick to researched science rather than personal speculation. I'm sure everyone can appreciate that this is a topic that attracts a lot of armchair evolutionary biologists.
    MarcoD if you have any scientific backing from that please provide it, otherwise it is far too speculative.
    Look up genetic drift, gene flow and mutation as well ;)
     
    Last edited: Sep 26, 2011
  15. Sep 27, 2011 #14
    I am not speculating, I am pointing out a weakness in the argument that homosexuality should eradicate itself.

    The scientific evidence is an ant society. Lots of ants are not involved in procreation, but that doesn't hurt the survival of that society.

    I.e., Darwinism doesn't always apply to the survival of the individual solely.
     
  16. Sep 27, 2011 #15

    Ryan_m_b

    User Avatar

    Staff: Mentor

    This is an example of http://en.wikipedia.org/wiki/Kin_selection" [Broken] for which there is little evidence in human sexuality. When I asked for evidence it was along the lines of "where is the evidence for how this phenomenon applies to homosexuality" rather than evidence of the phenomenon.
     
    Last edited by a moderator: May 5, 2017
  17. Sep 27, 2011 #16
    I also doubt that there have been many studies on that regarding homosexuality. But the burden of proof is on the original poster since he makes an assumption. He has the obligation to show that that assumption, which presupposes no kin-selection, is correct.

    In an odd twist, one might claim that homosexuality might be exactly that, since it didn't eradicate itself in the last couple of thousand years.
     
    Last edited by a moderator: May 5, 2017
  18. Sep 27, 2011 #17

    Ryan_m_b

    User Avatar

    Staff: Mentor

    This is something that has been studied, just type in "Kin-selection AND homosexuality" into pubmed, webofsci or google scholar. The evidence isn't there that there homosexuality is a product of kin-selection.
     
  19. Sep 27, 2011 #18
    In order to be eradicated by natural selection, homosexuality needs to be an heritable trait. But we don't exactly know how much of it is genetic.
     
  20. Sep 27, 2011 #19
    I stand corrected, it has been studied. At the same time, I googled it -as you suggested- and found evidence which also claim the contrary. So, I would say the evidence is out, either way.

    (http://www.news-medical.net/news/20100205/Kin-selection-hypothesis-may-explain-homosexuality-from-an-evolutionary-point-of-view.aspx" [Broken])

    Moreover, these are not the studies I expected. If I think about it, with a glass of wine, I would postulate an hypothesis that homosexuality gives an advantage to a society because of a) an added unique perspective to that society, b) lives dedicated to art and/or science, c) the manner in which a society learns to deal with 'others.' (I.e., not because it gives the direct relatives a Darwinistic advantage.)

    In short, maybe the Romans chopped off other people's heads because the other society never reached the advantage of having learned how to deal with puzzling other-beings. (The other society stood still in becoming more complex.)

    I personally believe it is just a result of the complex pheno- and genotype, but the above hypothesis might be true.
     
    Last edited by a moderator: May 5, 2017
  21. Sep 27, 2011 #20

    Ryan_m_b

    User Avatar

    Staff: Mentor

    Whilst there are studies that claim to support the kin-selection hypothesis I would say the case has not been made to consider it a candidate. As for your musings how would you explain homosexual behaviour in animals?

    EDIT: Actually don't answer that, we should keep conversation to mainstream science. Not personal theories.
    Judging by what we know now I would tentatively accept the hypothesis that the evolution of homosexuality is as a by-product of our capacity to have a sexuality and it hasn't been selected against because the advantage strongly outweighs the disadvantage.
     
    Last edited by a moderator: May 5, 2017
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Will evolution eradicate homosexuality?
  1. Human Evolution (Replies: 5)

Loading...