I am beginning to suspect that it is surprisingly common for intelligent, competent adults to somehow make it through the world for a few decades while missing some ordinary skill, like mailing a physical letter, folding a fitted sheet, depositing a check, or reading a bus schedule. Since these tasks are often presented atomically - or, worse, embedded implicitly into other instructions - and it is often possible to get around the need for them, this ignorance is not self-correcting. One can Google "how to deposit a check" and similar phrases, but the sorts of instructions that crop up are often misleading, rely on entangled and potentially similarly-deficient knowledge to be understandable, or are not so much instructions as they are tips and tricks and warnings for people who already know the basic procedure. Asking other people is more effective because they can respond to requests for clarification (and physically pointing at stuff is useful too), but embarrassing, since lacking these skills as an adult is stigmatized. (They are rarely even considered skills by people who have had them for a while.)
This seems like a bad situation. And - if I am correct and gaps like these are common - then it is something of a collective action problem to handle gap-filling without undue social drama. Supposedly, we're good at collective action problems, us rationalists, right? So I propose a thread for the purpose here, with the stipulation that all replies to gap announcements are to be constructive attempts at conveying the relevant procedural knowledge. No asking "how did you manage to be X years old without knowing that?" - if the gap-haver wishes to volunteer the information, that is fine, but asking is to be considered poor form.
(And yes, I have one. It's this: how in the world do people go about the supposedly atomic action of investing in the stock market? Here I am, sitting at my computer, and suppose I want a share of Apple - there isn't a button that says "Buy Our Stock" on their website. There goes my one idea. Where do I go and what do I do there?)
One theory is that there is a difference between sexual orientation and relationship orientation, so that there are men who prefer romance and relationships with women, but are sexually bi. Since our language and culture don't typically make this distinction, such people might just identify as straight.
Another is that sexuality is flexible, so in the desert island example, or in all-male environments, the men adapt over time to become capable of getting sexual satisfaction from other men in a way that they weren't before. This is similar, in a way, to the gradual-exposure techniques khafra talked about.
But -- and this was my main point -- before such a shift in sexuality occurs, a straight man would be out of luck even if he had 100 males to choose from. But once such a shift occurs, all he has to do is find one out of the 100 he's emotionally compatible with (assuming he's looking for emotional compatibility). This is why I said the sexual shift was the hard part: males are not an emotional monolith and out of 100, at least one should be more or less emotionally compatible.