@Garadox That was kind of straying into a different topic since the other poster was consistently denying that there are no problems with those kinds of relationships. I personally don't care if people want to do that sort of thing, it's their business how they live their own lives, but I wanted to point out that it simply is not the case that it's the same as more traditional relationships. Whatever the cause for it, something must be going wrong because it ends in divorce much more frequently.
As to the other part about what it means to be a man, I think we can't really get a concrete scientific definition of what a man is given that it's a more cultural and ideological idea, but what we can do is look back at the history of the idea of masculinity and what the great writers of old said on the subject to see if there's anything that stands out as consistently appearing, and among the cultural noise you do tend to get things like "providing for the family," among other things. I don't know that I'd say that's the only way to be a "real man" - after all, I think a single man who isn't married and has no children can also be a "real man" - but the idea that a man that does nothing to provide for at least himself is a failure is something that seems to be prevalent in most every culture across all of human history as far as I can tell.
I would also like to point out that I wasn't the one who made the original post, I was responding to somebody who posted something I found to be completely inaccurate.