Crying: Totatly unnatural (it's true)

Crying, I've heard something really interesting tears have evolved to simply moisten the eye ball, there is no psyiological reason to cry, so how's it happen? Is it a evolutionary mutation, could some people literally be unable to cry? Why does this psyiological response occur based on mostly psychological situations? My totally unscientific un researched thought is if it's not a natural function, when the first person cried did it invoke some visceral response which was seen as special, ergo they were protected, and as time and genetic evolution passed our protective urge, and crying itself became a part of the societal pattern? We know that the genes leading to survival tended to make it into the next generations, those that failed haven't made it into our genome as a dominant factor. IDk but if know anything about this or theory making sense of this please post, I'd love to include people thoughts on this in my dissertation.