Of course, humanity can be apportioned out in many different ways - male/female, old/young, hairy/bald and so on. Recently, I've discovered a new way.
When I tell someone one of my email addresses, it's about 20 letters, so I spell it out, there being no chance that they could guess the spelling. But I don't spell it out one letter at a time, that would be slow, tedious and, I think, insulting. So I give it to them in groups of four letters. Some people can't handle that, get muddled, confused, or get it wrong. So I drop down to give it to then in groups of two letters.
So that's the way that people divide - those that can handle four letters at a time, and those that can't.