How about you cut to the chase and say what you actually mean rather than asking a bunch of questions to try and tease me towards your point of view?

Save us all some time!
I answered this above anyway.
The main point of your answer was:
Because we have lived in a patriarchal society for a very long time.
Yes we have, however it didn't start that way, at some point society must have become patriarchal. Someone didn't just wake up in their cave at some point and think "you know what, I think a male's role is A, B, C, and a female's role is X, Y, Z" so there must be a reason for it.
"What I actually mean" as you put it, is that gender roles and social conventions aren't just there for the sake of it - there are reasons for it, and while you can say things like "there are women who are stronger than most men", that's the exception rather than the norm.
Again you can argue that that's purely down to nurture or enforced gender roles, but the fact is that men are genetically disposed to be physically stronger than women. This is
reinforced by society, and I'm not going to argue that point at all, but society is not the root cause.
There are other differences as well, for example women's superior ability to discern colour/shade - how is this caused by socially enforced gender roles?
Men and women are physically different - there's no arguing against that, and like it or not, it does mean they are better suited for different roles.
That doesn't mean that men can't do roles women are better suited to, and that women can't do roles that men are better suited to, it just means that the average woman will be better able to do a job they are better suited to than the average man, and vice versa.
I'm not sure why you're so intent on arguing that men and women are the same?
Different does not mean less equal. For example I like pizza, I also like sushi. Both are very different, however I like them both equally.
There's a whole wealth of information available on the web about gender role theory and it's origins. I'm not a sociologist so I'll let you do your own research to answer your question.
If you're not going to bother backing up your opinion, then why bother posting it all?