Essentially without science we can define women and men by saying women make babies and feed infants and men do not make babies or feed infants freeing them up to do other things with their time.
In my opinion, men are unique because they can impregnate a woman and not slow down, not get tired, need naps in the day or be short of breathe from holding something heavy. Men are unique because they do not have to nurse newborns every 2 to 3 hours, and lose sleep or mobility because of it. They are unique because they do not get pregnant and have to care for very young children and that uniqueness frees them up to explore the world in a way that women cannot without either abstinence or the use of science (ie. birth-control and formula). It frees them up to focus on bringing home the bacon while we focus on kids and the home.
That does not mean that women cannot bring home any bacon or that men can give no attention or nurturing to kids; but it does mean that we naturally have different focuses. And we can choose to acknowledge this and work together with this knowledge or we can ignore it and try to work against it; but in the end I think our biology does not change as quickly as science has or as quickly as mainstream feminism would like it to change.