Women's best marathon times are about 10 minutes behind men's. However, records for women have only been kept since 1964. The best times for men have improved by a yearly increment of 66 seconds, whereas the best times for women have improved by a yearly increment of 2 minutes and 47 seconds. It would seem as though women are racing to catch up with the men. Another change that has occurred recently is that women are now frequently participating in sports that were previously thought to be only for men, such as ice hockey and boxing.
Women are probably capable of excelling in all sports that require skill as opposed to pure brawn.
Some women are even excelling in sports that emphasize muscle strength over skill. The most likely explanation is that women are just lagging behind because they have not had as much practice or as much time to improve in these areas as men have. Given enough time, support, and encouragement, women may be able to compete equally with men in many sports.