Just a question that popped into my head and that Google doesn’t seem to have a quick answer to right now. Also I’m 99% I made a grammatical mistake in that title, so I apologize beforehand.
Not necessarily. There are cases of identical twins with different orientations
There appear to be genetic and developmental components to sexual orientation, so there’s no certainty. Identical twins are essentially clones and they don’t always have the same orientation.
From what I understand:
Identical twins are more highly correlated than fraternal twins.
Fraternal twins are more highly correlated than non-twin siblings.
Non-twin siblings are more highly correlated than unrelated individuals.
Which implies that there’s at least some component of sexuality that’s genetic, at least some component that’s due to the uterine environment (presumably hormone exposure), and at least some component that’s neither genetic nor uterine.
Of course, all of this has large error bars, because there’s no way to reliably and objectively determine someone’s sexual orientation. Most studies are based on self-reporting, but some people lie about their orientation, even in anonymous studies.
Thank you all for your information! I’m on a cloning kick right now and have more questions, but they’re more “Great Debates” than factual.
So, are you @Love_Rhombus or a clone of @Love_Rhombus? What is board policy for cases where a clone posts under the original’s user name?
For all you know, I could be a clone of you (or vice versa)!
I’m sure @Cecil_Adams has some sort of rule about clones posting.
My nephews are identical twins (or appear to be - I could never tell them apart when they were young). one is straight, one is gay.
One explanation I saw for orientation is to think of it like software. There’s a chunk of brain like a software module that recognizes “this is a hot female” and one that recognizes “this is a hot male” (along with all the associated physical desirability characteristics and urges that develop at puberty, etc.). Our minds are full of these “modules” like the ones that say “babies and puppies - cute” or the ones that say “eyes in the darkness out there - bad!” or “snakes and creepy things - bad”. They are part of our deep instinctive programming. The process of development should determine which module gets “connected” in the brain due to genetic makeup - but sometimes the opposite gets selected. Correlation - or the propensity to mix up the orientation vs genetics - is perhaps to some extent a genetic trait, so hence the different levels of correlation depending on relatedness. basically, it’s random but maybe genetics loads the dice in that connection randomness.
There’s a book (“Everyone Lies” by Davidovitch) where he examines anonymized Google searches. In one chapter, he mentions that based on other searches, they can guess who are male - and regardless of the social climate of openness or repressiveness, in private consistently about 5% of males search for gay porn. Implication, about 5% of males are gay regardless of cultural forces or environment. (Women are harder to figure because apparently straight women are more willing to search for lesbian porn also).
To make sure I’m understanding you correctly, the fraternal twins being more highly correlated than non-twin siblings is where the uterine environment component comes in, right? Because if it weren’t for the uterine environment, fraternal twins ought to have the same correlation as non-twin siblings?
How are they figuring that a man who googles gay porn is gay? Not sure how they’re concluding that a woman who googles lesbian porn isn’t necessarily gay, but a man that googles gay porn is necessarily gay.
“It was research for a book, I swear!”
Even assuming that straight men don’t ever search for gay porn, it seems extremely likely that bisexual men would do so. So that 5% number would at a minimum include gays and bisexuals.
Such numbers and inferences are by nature imprecise. I Have no idea what bi males will search for. Presumably, most times, people will search for that which most turns them on.
Well I do have an idea.
As you say, “most times, people will search for that which most turns them on”. Since bi men are turned on by both males and females, it’s a pretty good bet that they would search for both forms. (Sometimes for one, sometimes for the other, depending on their mood at that time.)
There are also tests based on monitoring the rapid movement of the eyes: You show the subject an array of pictures, and the pictures their eyes spend more time on are presumed to be the pictures they find more pleasing. But ultimately, any way of measuring sexual preference is going to be imprecise.
The same book also mentions that the biggest insecurity–related search for men is “is my penis too small?” So presumably every straight male will scan pictures of naked men if presented to them, to judge penis size, thus negating this test. 
(And the equivalent insecurity search by females is “why does my vagina smell?” Nothing to see here, until Google perfects smell-o-vision)