I guess the easy answer is what some have said, which is PEDs. There has got to be some truth to that becasue a woman can take relatively small amounts of male harmones and get a significant boost. I use to work out with a female bodybuilder who had more muscle than me as she brough her PEDs from the local drug store.
In America, I think we are seeing the effects of title 9. A high school girl who can run a 5 minute mile can get a D1 scholarship. While that is only equal to about a 4:25 mile for boys, yet a boy would have to 4:15 to get a D1 scholarship. I have actually known H.S. girls who did other sports and started running track in their Jr year to get money for college and ended up getting scholarship money. The other thing, there is a female running boom going on in America. There are now more women who run road races than men and these women are getting there daugthers into running.