My 10-year-old daughter and 40-something wife seem to be going through similar stages. I believe scientists call it the "boys are yucky" phase. My daughter's symptoms include never touching boys, unless it involves poking, going through the school yearbook to point out which boys are the ugliest and most annoying, and occasionally comparing notes with other girls about which boys they "like-like." A little unrequited flirtation adds some spice to an otherwise monolithic wall of gender disdain.
My wife's condition manifests similarly. It's evidenced by girls-only vacations and nights-out, going through lists of men to identify which are least interesting and most annoying, and practicing a platonic form of "safe sex" by including in the group at least one non-threatening but hilarious gay man. A little testosterone keeps things jumping. Just not too much.
Being on the male side of this divide, I'm left wondering if there's some evolutionary purpose to gender segregation. My daughter is at the beginning of puberty; my wife post-menopause. Perhaps an absence of fertility renders straight males useless. Or maybe there are periods in life when each of the genders can best decide who they want to be by learning from same-sex interactions. Divorce rates peak in the mid-40s, perhapst because that's when women need to drift back to their pre-pub roots, more interested in whatever it is that men previously had to offer.
Ten-year-old boys seem to go through a stage of their own, which might be termed the "what's a girl?" phase. They're too busy playing sports or poking one another to notice that virtually the entire girl population -- expect a few sporty, cross-over types -- don't give them no never-mind. And my mid-life male peers are mostly returning to their own boyhood behaviors, busily chasing balls, though the goal posts are mostly defined by bank account balances. Those who aren't are in the midst of their own pre-pubescent-like identify crises, except rather than staring at their face in the mirror in search of emerging pimples, they look for the next wrinkle. Either way, they're too absorbed in their own distractions to notice that the girls aren't paying attention to them anymore.
As for me, I grew up with three sisters, so I am used to being variously the object of spirited affection and neglectful abuse, and giving back the same. And anyways, I'm busy researching hair loss remedies.