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Identical twin studies point away from genetics very hard. Pretty much all genetic anomalies will affect both identical twins 100% of the time. The fact that i

by hajile 6y ago

Identical twin studies point away from genetics very hard. Pretty much all genetic anomalies will affect both identical twins 100% of the time. The fact that it's less than 40% points much more to environmental effects rather than genes.

mr_overalls 6y ago
A concordance rate of 40% actually points to a near-even split between heritable and non-heritable factors.
drocer88 6y ago
From the link: "Research from the 1990s2 showed that identical twins are more likely to share a sexual orientation than are fraternal twins or adopted siblings." Study here : https://pubmed.ncbi.nlm.nih.gov/9549243/ https://pubmed.ncbi.nlm.nih.gov/9549243/ "We present an overview of behavioral genetics research on homosexual and heterosexual orientation. Family, twin, and adoptee studies indicate that homosexuality and thus heterosexuality run in families. "
- jdgoesmarching 6y ago
  This thread seems very insistent on pushing the environmental case when presented with evidence to the contrary. It’s like I stumbled into a Republican convention in the 90s. Baseless theories: people do this to feel better about LGBT discrimination or the idea of sexuality being out of our control is too scary for dudes who haven’t come to terms with their own masculinity. The latter isn’t necessarily shade, I’m not sure I figured it out until my mid-20s.
  - coldtea 6y ago
    Hello, 1990 called. It's 2021, gender (including sexuality) is fluid. And yet, it's the other commenters who seem backwards to you?
    - ravi-delia 6y ago
      I'm really not seeing anything in the above comment that indicates they don't see gender as fluid.
      - coldtea 6y ago
        "pushing the environmental case when presented with evidence to the contrary" Parent wants to push the "fixed gender" case instead.
  - Itsdijital 6y ago
    It goes beyond that. The fear is that genetics will show that people are in fact not blank slates, and even further that there advantageous and disadvantageous traits common to groups of people. I'm sure you can surmise the implications of this. Evolutionary biology has been making steady gains in the "nature not nurture" department and it has become an absolute lighting rod to discuss.
  - arp242 6y ago
    You can believe that homosexuality is at least partly environmental while also believing that people should have the freedom to be as gay as they want to be. I don't really like these appeals to motive; this is quite an interesting empirical question that's disconnected from discrimination. Even if it would turn out that homosexuality is a choice (I don't think it is, but let's assume it would be) then this wouldn't change my position one iota. People choose whether to smoke weed or not, and I also think people should have the freedom to choose to do so. I'm not so sure what the evidence says on this, but it appears it's less of clear-cut "it's 100% genetic" than it seems to be. These things are notoriously hard to study. The real problem seems to be that people are afraid that the "God hates fags" people will run with these kind of things, but these people will do their thing anyway no matter what the science says on account of being homophobic twats.
    - Neeek 6y ago
      I'm a little confused, you seem to be using choice and environment like they are synonymous here. It's a small nitpick but, even if this is environmental or epigenetic it doesn't necessarily mean that people get to choose the environment they exist in, at least in their formative years.
      - supercheetah 6y ago
        That's not at all what was being said. The question of what causes homosexuality or heterosexuality is an interesting scientific question. Even if it were purely by choice, that doesn't reflect on any other characteristic of a person, and any fear that homophobes might try to use some hypothesis or another for their propaganda doesn't matter because they don't care about science anyway.
      - arp242 6y ago
        Reading my post again, I probably could have chosen some better wording here and there. However, the point is that it doesn't matter if homosexuality is either environmental or a choice: the effects people having gay sex remains the same: people have gay sex with no negative consequences to anyone at all. Nothing more. And therefore they should have the freedom to have as much gay sex as they damn well please. Everything else is, quite frankly, just bullshit. As I pointed out in my other comment[1], I definitely chose to have gay sex at some point and certainly could have chosen not to. I don't think it's so black/white. [1]: https://news.ycombinator.com/item?id=26073364 https://news.ycombinator.com/item?id=26073364
  - mehwoot 6y ago
    "environmental" doesn't mean it's a choice or that it can be effectively changed. For example environmental factors during pregnancy could have influence, but once someone is born it could be mostly determined. That would be entirely consistent with sexuality being somewhat genetic, mostly environmental, but unable to be changed after birth.
  - hn_throwaway_99 6y ago
    To be honest, as a gay man, I find the opposite is often true: that somehow insisting on homosexuality being genetically preordained is needed in order to argue against sexual-orientation-based discrimination. That is, if it is an inborn trait then gay people shouldn't be discriminated against because they "can't help it". I've always found that somewhat offensive, because it somehow takes the sub/unconscious opinion that being gay is defective: "You wouldn't discriminate against someone with a severe birth defect, well gay people can't control it either." Fuck that. Whether it comes about from the genes, or through the environment, or most likely through some combination of the two, it is completely illogical for anyone who has ever felt sexual attraction of any kind to argue that it can "controlled", so I don't need some appeal to "it must be in my genes" to make me feel better.
    - MaxBarraclough 6y ago
      Also, there are already protected classes that are partly or wholly matters of choice. Religion, pregnancy, familial status, veteran status. On a related note, I don't see that the is it a choice? question is even meaningful in the first place. Preferences aren't generally something we get to choose. I could probably learn to like some unfamiliar genre of music simply by listening to a lot of it, but you could offer me a heap of money to like the PHP programming language and I'd still be unable to do so. My opinion of it isn't something I can so easily will to change.
rootusrootus 6y ago
My nephews are monozygotic twins. One is very straight, and the other is very gay. They happen to be mirror image twins. This points towards genetics.
- deleted 6y ago
  [deleted]
- xvedejas 6y ago
  By "mirror image", do you mean very identical looking, or do they also have different handedness or something? I could go 50/50 on this being some term for twins I haven't heard before.
  - rootusrootus 6y ago
    I mean mirror image twins. Approximately 25% of all identical twins are mirror image twins. Or mirror twins, or opposite twins. There are a few different terms for the same phenomenon. The exact cause is unknown but it's theorized that mirror image twins happen when the zygote splits a few days later than 'normal'.
- makeworld 6y ago
  This is an anecdote.
onlyrealcuzzo 6y ago
Is handed-ness environmental or is it genetic? It doesn't seem likely to be environmental... 21% of Monozygotic twins are left-handed when the other is right-handed. This is higher than the general population. Aren't there plenty of genes that just lead to higher causes of something? There are identical albino and non-albino twins. I'm really skeptical that albinism is environmental. But stranger things have happened, I suppose.
monkeypizza 6y ago
When the population base rate is low, and being genetically identical increases the rate to 40%, that is a strong argument that it's highly genetic. The effect only gets stronger to the extent the 40% is from environments where people would be reluctant to admit to homosexual experiences.
ravi-delia 6y ago
I'd say that that's probably more than a little bit of a simplification. Sexuality is almost certainly extremely polygenetic, interacting with the environment in all sorts of miserably complicated ways. Plus, the standard twin study design winds up counting pretty much all error as environmental.

by hajile 6y ago

mr_overalls 6y ago

A concordance rate of 40% actually points to a near-even split between heritable and non-heritable factors.

drocer88 6y ago

From the link: "Research from the 1990s2 showed that identical twins are more likely to share a sexual orientation than are fraternal twins or adopted siblings." Study here : https://pubmed.ncbi.nlm.nih.gov/9549243/ https://pubmed.ncbi.nlm.nih.gov/9549243/ "We present an overview of behavioral genetics research on homosexual and heterosexual orientation. Family, twin, and adoptee studies indicate that homosexuality and thus heterosexuality run in families. "

jdgoesmarching 6y ago
This thread seems very insistent on pushing the environmental case when presented with evidence to the contrary. It’s like I stumbled into a Republican convention in the 90s. Baseless theories: people do this to feel better about LGBT discrimination or the idea of sexuality being out of our control is too scary for dudes who haven’t come to terms with their own masculinity. The latter isn’t necessarily shade, I’m not sure I figured it out until my mid-20s.
- coldtea 6y ago
  Hello, 1990 called. It's 2021, gender (including sexuality) is fluid. And yet, it's the other commenters who seem backwards to you?
  - ravi-delia 6y ago
    I'm really not seeing anything in the above comment that indicates they don't see gender as fluid.
    - coldtea 6y ago
      "pushing the environmental case when presented with evidence to the contrary" Parent wants to push the "fixed gender" case instead.
- Itsdijital 6y ago
  It goes beyond that. The fear is that genetics will show that people are in fact not blank slates, and even further that there advantageous and disadvantageous traits common to groups of people. I'm sure you can surmise the implications of this. Evolutionary biology has been making steady gains in the "nature not nurture" department and it has become an absolute lighting rod to discuss.
- arp242 6y ago
  You can believe that homosexuality is at least partly environmental while also believing that people should have the freedom to be as gay as they want to be. I don't really like these appeals to motive; this is quite an interesting empirical question that's disconnected from discrimination. Even if it would turn out that homosexuality is a choice (I don't think it is, but let's assume it would be) then this wouldn't change my position one iota. People choose whether to smoke weed or not, and I also think people should have the freedom to choose to do so. I'm not so sure what the evidence says on this, but it appears it's less of clear-cut "it's 100% genetic" than it seems to be. These things are notoriously hard to study. The real problem seems to be that people are afraid that the "God hates fags" people will run with these kind of things, but these people will do their thing anyway no matter what the science says on account of being homophobic twats.
  - Neeek 6y ago
    I'm a little confused, you seem to be using choice and environment like they are synonymous here. It's a small nitpick but, even if this is environmental or epigenetic it doesn't necessarily mean that people get to choose the environment they exist in, at least in their formative years.
    - supercheetah 6y ago
      That's not at all what was being said. The question of what causes homosexuality or heterosexuality is an interesting scientific question. Even if it were purely by choice, that doesn't reflect on any other characteristic of a person, and any fear that homophobes might try to use some hypothesis or another for their propaganda doesn't matter because they don't care about science anyway.
    - arp242 6y ago
      Reading my post again, I probably could have chosen some better wording here and there. However, the point is that it doesn't matter if homosexuality is either environmental or a choice: the effects people having gay sex remains the same: people have gay sex with no negative consequences to anyone at all. Nothing more. And therefore they should have the freedom to have as much gay sex as they damn well please. Everything else is, quite frankly, just bullshit. As I pointed out in my other comment[1], I definitely chose to have gay sex at some point and certainly could have chosen not to. I don't think it's so black/white. [1]: https://news.ycombinator.com/item?id=26073364 https://news.ycombinator.com/item?id=26073364
- mehwoot 6y ago
  "environmental" doesn't mean it's a choice or that it can be effectively changed. For example environmental factors during pregnancy could have influence, but once someone is born it could be mostly determined. That would be entirely consistent with sexuality being somewhat genetic, mostly environmental, but unable to be changed after birth.
- hn_throwaway_99 6y ago
  To be honest, as a gay man, I find the opposite is often true: that somehow insisting on homosexuality being genetically preordained is needed in order to argue against sexual-orientation-based discrimination. That is, if it is an inborn trait then gay people shouldn't be discriminated against because they "can't help it". I've always found that somewhat offensive, because it somehow takes the sub/unconscious opinion that being gay is defective: "You wouldn't discriminate against someone with a severe birth defect, well gay people can't control it either." Fuck that. Whether it comes about from the genes, or through the environment, or most likely through some combination of the two, it is completely illogical for anyone who has ever felt sexual attraction of any kind to argue that it can "controlled", so I don't need some appeal to "it must be in my genes" to make me feel better.
  - MaxBarraclough 6y ago
    Also, there are already protected classes that are partly or wholly matters of choice. Religion, pregnancy, familial status, veteran status. On a related note, I don't see that the is it a choice? question is even meaningful in the first place. Preferences aren't generally something we get to choose. I could probably learn to like some unfamiliar genre of music simply by listening to a lot of it, but you could offer me a heap of money to like the PHP programming language and I'd still be unable to do so. My opinion of it isn't something I can so easily will to change.

rootusrootus 6y ago

My nephews are monozygotic twins. One is very straight, and the other is very gay. They happen to be mirror image twins. This points towards genetics.

deleted 6y ago
[deleted]
xvedejas 6y ago
By "mirror image", do you mean very identical looking, or do they also have different handedness or something? I could go 50/50 on this being some term for twins I haven't heard before.
- rootusrootus 6y ago
  I mean mirror image twins. Approximately 25% of all identical twins are mirror image twins. Or mirror twins, or opposite twins. There are a few different terms for the same phenomenon. The exact cause is unknown but it's theorized that mirror image twins happen when the zygote splits a few days later than 'normal'.
makeworld 6y ago
This is an anecdote.

onlyrealcuzzo 6y ago

Is handed-ness environmental or is it genetic? It doesn't seem likely to be environmental... 21% of Monozygotic twins are left-handed when the other is right-handed. This is higher than the general population. Aren't there plenty of genes that just lead to higher causes of something? There are identical albino and non-albino twins. I'm really skeptical that albinism is environmental. But stranger things have happened, I suppose.

monkeypizza 6y ago

When the population base rate is low, and being genetically identical increases the rate to 40%, that is a strong argument that it's highly genetic. The effect only gets stronger to the extent the 40% is from environments where people would be reluctant to admit to homosexual experiences.

ravi-delia 6y ago

I'd say that that's probably more than a little bit of a simplification. Sexuality is almost certainly extremely polygenetic, interacting with the environment in all sorts of miserably complicated ways. Plus, the standard twin study design winds up counting pretty much all error as environmental.