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To oversimplify, one could posit a genetic set up where there are two genes contributing; each parent might be 40% influenced towards being gay, but function as heterosexuals. Their child might then get the characteristics of both and be 80% influenced towards being gay.

There’s absolutely no proof of this. In fact, the twins studies prove just the opposite. Identical twins have never had a 100% concurrence rate, at best only a 0-50+%.

If you look back at my posts, I was giving this as an example of how in some heritance schemes, there are multiple genes involved. A previous posted seemed to be under the impression that inheritance was based on single genes in an "on/off" scenario. I specifically said that I was not indicating that such inheritance was necessarily proven to occur in this case.

There's no possibility for a 100% concurrence rate in identical twins because you're ignoring the influence of environment on genes which is what I was talking about. In the womb even in identical twins one twin gets more of the nutrients because of where it's connected to the placenta. And once they get out--some will be exposed to different viruses, bacteria, they'll have different food tastes (even Siamese twins historically often have different food cravings). Genes are a big part of the picture but they don't operate like little widgets, they are influenced by the environment which is chemical, biological, hormonal, experiential, emotional etc etc

When you see a significantly higher than chance concordance (i.e. among identical twins, and higher than normal but not as high on fraternal/siblings, and less as you become less genetically allied)_....then you know genes are at work. It isn't 100%....

Yegads, freeps, get some of your science right!