Eye-dominance is a critical thing with bows: right-eye-dominant is recommended to do the aiming on the right eye here otherwise inaccuracy. This made me think whether all people are even able to do this. I have seen people who can only close one eye or two eyes at the same time but not two eyes separately. What is the factor determining this? Is this determined by genes, learning or by something else? Is it possible that the other side of the eye muscles are missing because they have not been needed for the survival? I discussed missing muscles with my medical friends and they mentioned that there are muscles that some people do miss such as in hands because they are not essential for survival. I don't know whether certain muscles in face could be missing with some people or is this just learning thing?