How do people who were born blind know how to have sex?
Think about it. For me sex is very visual, I know I have a sex organ that is male and I know I like other humans with sex organs that are female.
If you're born blind, you've never even seen a female, so theoretically you could just as easily be homosexual as you've never seen anything.... You can only touch, smell, taste and hear.
Beyond all of that, how do you know where to put your sex organ and how to behave during sex.
Is it instinctual?