Just for perspective: I am a man in my mid-40s and for as long as i can remember i had this question… is it normal that i can shut my nose close just with some muscles?
I always wondered why some people hold their nose shut with their fingers while jumping into a pool or when exposed to some horrible smell… i never had this need. Changing my sons diapers? No problem! Cleaning the latrines while in the army? Just a breeze!
Ehm… yeah… just thought about this…
I think some of those are genetic.
Might be, but all of these are things I was not able to do at some point and that I conciously learned. So while having the “wrong” genetics might preclude you from doing them, you still need to learn these things if you have the “right” genetics.