Skip to content

An interesting number

The researchers found same-sex behaviour in males was 6.4 per cent heritable, the first evidence of homosexuality being genetic in primates.

Strict homosexuality is, of course, not directly heritable (although there’s always that argument aht gay uncles provides some benefit).

But this 6.4%. In this field is that a big number or not? Compared to, say, blue, brown eyes? Or height. Or, that thing we keep being told isn’t heritable, intelligence?

22 thoughts on “An interesting number”

  1. Errrrr
    We are talking about Imperial College (red flag).
    Doing research on (i.e. watching) a bunch of monkeys in Puerto Rico for more than half a century.
    Who weren’t even given the opportunity, via their lawyers, to dispel this vile slur.

    Still, Stonewall will be delighted. Just as long as a sufficient number of the macaques choose to wear makeup and enjoy watching the reboot of sex in the city.

  2. As a rule of thumb, if you don’t know whether a complex trait is genetic or environmental, presume 50:50. When you actually start gathering evidence things seem to mostly fall between 25:75 and 75:25, i.e. there’s nothing totally genetic and nothing totally environmental/cultural. 6.4% is very low.

  3. Suggest that being keen on sex is heritable.
    if the target of that enthusiastic interest very occasionally turns out to be the same sex ,that is of no consideration from the point of view of evolution and the species.

  4. Scientists claim the very common behaviour of ‘same-sex mountings’ leads to improved social bonds and relationships

    We can learn so much from disgusting little animals that fling their own poo.

  5. Personally, I reckon the concepts the whole thing’s based on are flawed.
    1) Sex is pleasurable
    2)It’s more pleasurable when another/more individuals are involved.
    3)As far as the pleasure’s concerned, it doesn’t matter what sex the other individual(s) are.

    So the norm for pleasurable sex should be bi-sex. Exclusive heterosexuality/homosexuality are aberrations.
    However, there is a lot more going on than just sexual pleasure. Territoriality, pair bonding, peer group hierarchy & domination/submission, female/male pheromone attractiveness/repulsion.
    So for the monkey’s in question, you’d have to look in amongst that list. (Humans, you might add societal pressures)
    So it’s never about whether some individual’s “gay”. It’s more about why they’re not.

  6. Re your post Apropos No Names, I believe the legal age for distributing porn is 18. That seems to be the crux of the problem. It looks like someone is trying on a shakedown by technicality

  7. Doing research on (i.e. watching) a bunch of monkeys in Puerto Rico for more than half a century.
    Wonder who paid the money for that? They’d want something for their money, wouldn’t they?

  8. Bloke in the Fourth Reich

    6.4% heritable (implausible accuracy red flag) is really not heritable at all. Likely the confidence interval includes 0%.

    Or perhaps even negative heritability, which would, as observed, be expected for such a behaviour.

  9. A decimal point – must be accurate, like the decimal point in global temperatures… reassuringly scientific.

  10. Sort of what BiS says..

    In mammals, especially the ones that do the social group thing, sexual behaviour is invariably tied heavily into the behavior that makes the group dynamic work.
    This is most noteable in behaviours like dominance and friendships/cooperative team-ups, but there’s a host of “sexual” behaviours that have been re/dual-purposed to make that group cohesion work.
    Most of which are, in fact, “unisex”.

    It’s a simple fact that sex, and the associated courting behaviour, triggers a ton of serotonins and opioids to be released in our mammal ( and not just mammal.. it’s built in from pretty far back down the evolution tree..) brains that are pleasurable to the point of being addictive.
    Great for not being attacked or eaten by your potential partner. Also works great to defuse stress between individuals in a group, which is why it’s been repurposed in that way: the system was already there, and Mother Nature is not a fan of re-inventing the wheel..

    Of course, in social animals that do not have a breeding season, this behaviour overlaps continuously, like those macaques, or us, or really any of our primate cousins. Basically anything (originally) predatory with a social structure in/from the (sub)tropical belt.
    With the Bonobo Chimps (actually the most psychopathically dangerous of our cousins..) having turned this into a fine art. To stop them from killing each other at the drop of a hat…

    As for that 6.4%.. Sounds about right.
    There is a hereditary component to this behaviour. After all, the basics of this behaviour are hardwired into our brains, in several places, with each their own probability distribution of “going wrong”, with varying expression levels, which overlap in causing the root behaviour, which can be modified/suppressed by group dynamics/experience…

    That 6.4% is smack in the middle of the 5-7% expression rate of homosexual and bisexual behaviour in humans combined if you add up the real numbers. And pretty close to what had been found in rough guesstimates in lions, hyenas, chimps… the list goes on..
    Thing is… This doesn’t prove any of this is hereditary, other than proving that general statistics works as intended: If you throw a stack of d6’s a lot of times, you get that lovely bell curve.
    You can work out the probability of a high/low result, but you cannot pinpoint any particular dice to cause this result.

    And given that we know Mother Nature uses a huge pile of dice, shaken very hard, using a couple of tricks to prevent/suppress parental behavioral ( and physical ) traits to express in their offspring…
    (This is why you “take after” your (great)grandparents/uncles/aunts/cousins xremoved, but rarely ever one of your parents…)
    Good luck pinpointing any gene/gene complex that causes Behaviour X…
    That’s still a bit of a Holy Grail in biology.. And one we’re not going to find pretty soon..

  11. @Grikath.
    I don’t think you’re ever going to find a gene for homosexuality. You’d have more luck looking for the genes result in the behaviour that suppresses it. But since there’s so many factors…

  12. @BiS A gene for “homosexuality”? Nope. Not ever.

    Actually proven to be impossible, simply because actual science has already roughly identified several areas of the brain that govern sexual attraction/sexual identification.
    Some of which are “unrelated” when it comes to development.

    So when it comes to genes ( and genetic inheritance ) you’re already talking about multiple genes which may or may not be related/commonly controlled, of which several cannot share any common control, because their potential activation happens in a different stage of development.

    Actual suppression… Just my opinion, but that would actually mostly be on the Nurture side of things.
    The suppression of “Unwanted Behaviour” and the promotion of “Wanted Behaviour” by the group/society at large.
    The finetuning of those basic/blueprint neurological networks of the infant into a functioning member of the group.

    Which, as history proves through the Greeks and Romans ( and the Nordic Tribes before christianity, and the Mongol Hordes, and the Huns, and, not forgetting, the Ottomans…) , can and does include “homosexual behaviour”.
    Clearly tied to dominance behaviour and warrior cultism, but very much homosexual behaviour nonetheless.. Even though they all, very much, despised effeminate gays/trans at the same time..

    But yeah… so many factors.. Which makes it an insanely interesting multidisciplinary field to keep a toe in.
    Now if we just could feed the Woo crowd to the Lions, we might actually make some progress in this..

  13. Any observation that homosexuality cannot be inherited is nonsense. Consider two individuals. One is strictly heterosexual and has hetersexual sex once every two years, while the other is homosexual and has homosexual sex daily, but once a year also has heterosexual sex. Clearly the latter will have a better chance of leaving descendants. Evolution does not penalise homosexual sex – it encourages heterosexual sex. But in many animals the amount required to breed is far, far below the amount of sex actually performed (even if it is heterosexual).

  14. that would actually mostly be on the Nurture side of things.
    There’s a whole lot of factors like territoriality & hierarchical behaviour seem to be hardwired in on the genetic level. Since they’re common across so many different species. There are baehavious that are connected to them that are homosexual in some species. But that’s more about establishing dominant/submissive relationships in hierarchies than mutual pleasure. Again likely hardwired in rather than nurtured. The dog humping your leg thing. I can assure you, they don’t have to learn it from other dogs.

  15. Incidentally, you cure that by grabbing the dog by the neck & putting it on its back on the floor. Shouting & the odd slap help. It’s the dog trying to achieve dominance, so you put it in a submissive posture. Pushing it off & saying “naughty boy” achieves the opposite.

  16. If it is a genetically heritable trait, it might be a recessive one. That is, a child would have to inherit the tendency from both parents. And if they only inherited the gene from one parent, they could still have the tendency lurking within them, ready to pass on to their own offspring.

    In fact, if it involves two genes from each parent, the way inheritance of blue eyes does, you’d get roughly the same proportion of homosexuals in the population as you do in reality. And recessive genes would explain why such an evolutionary disadvantageous behaviour doesn’t disappear.

    As ever on this blog, I’m happy for people who do actually understand this stuff to point out my errors.

  17. Charles… As usual you come up with stuff that sounds really smart in Debating Club, but is actually complete and utter bovine exhaust product if you look at the actual engineering inside what to you is obviously a Black Box you can ventilate your views on.

    Paul, there have been cases (more or less voluntarily in the US, less so behind the Iron Curtain when it still stood.. And no-one dares mention the late 19th, early 20thC, or the post-War era, where … Things were Tried… that were deemed “acceptable” at the time…) where the heredity of homosexuality was actually tested.
    Specifically the recessive-factor theory.

    And yes… You need to hook up a confirmed gay with a confirmed dyke, and have them have offspring to test that one. Guess what the techniques used in artificial insemination were trialled on in many places..
    At least the modern cases in the US revolve around lesbian women choosing to be knocked up by confirmed gay donors ( with a little help from a syringe..) to “maximise the chance” to get a homosexual child… ( hopeless, because, but still, it’s self-inflicted Free Choice..)

    And guess what… The traits, if any, do not inherit according to the Mendelian model.
    In fact, the first generation is less likely to be homosexual, to almost the point of exclusivity for heterosexual behaviour.
    Which stumped people until the actual mechanism behind it was figured out in the late 1980’s: Meiotic Editing.
    Those skip-a-generation traits that can even suppress a Dominant gene, allowing the recessive counterpart free reign in an individual if present.

    Because this vastly complicates the math around “will (s)he/won’t (s)he”, there’s several models around guesstimating the factors involved ( we haven’t actually found any..), of which one likely candidate actually revolves around a Dominant gene (with coupled, recessive “satellites”) with low incidence that gets preferentially shut down during meiosis in the male.
    This one has the Woo Crowd in offended tremors, since it assumes that there’s a different genetic basis for male and female homosexuality to begin with.
    Which may well be the case, but tell that to the Woo Crowd…

    All it shows is that “genetics” very much isn’t the stuff peeps get taught in highschool, and that the shenanigans Mother Nature gets up to to maximise genetic diversity are varied and many.
    There’s a solid reason molecular genetics is a specialism not many people care to tackle…
    It’s damn hard, extremely complicated, and being well into the Fundamental Research territory, has lousy pay and career opportunities.
    Especially since there isn’t much chance of new breakthroughs (and fancy science awards/eternal fame), but an overdose of tons and tons of actuarial work counting, labelling, and categorising the various bits and their interactions/dependencies.

  18. Straight porn mags, which is basically porn for straight blokes, have pictorials – the first two shots are of a real woman in a dress, then a negligee perhaps or just a nipple, then knickers then not much.
    The gay porn pictorials, and I’m assuming the winning publications used to satisfy a certain market before the internet, didn’t do any visual foreplay, not even for half a page, it was just bang in.
    Can’t explain it, no suits or uniforms, just straight at it.
    Probably linked to promiscuity but the underlying cause, what is it.

    But never mind that – do societies that are the most permissive or the ones that are the most repressive have the most gayers at the 2nd and 3rd generations. Geneticists and sociologists need to step up and figure it out. Grant funded trip to Zimbabwe available surely.

  19. Thanks for that, Grikath. My knowledge of biology was zero before, but at least now I know a bit more about what nobody else knows.

    The only reason I know anything at all about dominant and recessive genes is because I once put a racemare in foal, and I was curious about how two bays occasionally produce a chestnut. (Thoroughbred coat colour is about as simple as it gets – one gene from each parent, bay dominant, chestnut recessive).But I’d never come across the notion that it might not be an even money shot which of the two genes gets passed on, nor that the odds vary by sex.

    As you say, it makes the calculations hideously complicated.

  20. Bongo:

    do societies that are the most permissive or the ones that are the most repressive have the most gayers at the 2nd and 3rd generations. Geneticists and sociologists need to step up and figure it out. Grant funded trip to Zimbabwe available surely.

    Don’t need trips to Zimbabwe for that.. The most repressive societies regarding homosexuality in any measureable way that have been going on long enough to have a chance of actually measureable/traceable numbers and incidences, followed by a “renaissance” which swung the pendulum the Other Way are….

    The UK and the US , late 19thC to early 1960’s.. And then the 1960’s on to current…

    Pretty good to excellent records on pedigree and parentage, plenty of court records regarding incarceration and other Nasty Things We’d Rather Not Talk About, and more than sufficient people to do Statistics on..

    And plenty of Literature where people have crunched those numbers..
    Of course.. Requesting those in the UK might get you Looked At, quite disapprovingly. Possibly followed by a Sternly Worded Letter.
    Good thing other national libraries have full copies of the Proceedings of the Royal Society… And less anal retention when it comes to scientific gaffes perpetrated by the British..

Leave a Reply

Your email address will not be published. Required fields are marked *