Speaking for myself as a heterosexual male, I don't notice myself categorizing other men in terms of alpha/beta traits. When I meet people, I pay more attention to whether I have something in common with them (values, interests, etc.).
What I've read is that the alpha/beta distinction (although not necessarily the terminology) is created by women in the sense that they see certain men as being sexually attractive (these are called alphas) and other men as being attractive in more non-sexual ways, like stability, reliability, etc. (these are called betas). A man who's never or rarely regarded as attractive by women has some other Greek letter.
On your question about science, I know of no science behind this. It seems to be just a cultural understanding of sorts.
