This is basically the "you throw like a girl" phenomenon. With a sister who played NCAA Division I varsity softball, I can assure you that girls can learn to "throw like a boy", and then some. And yet, many more girls than boys "throw like a girl" (hence the stereotype). The reason is simple: throwing well takes practice, and boys throw more than girls.

But why do boys throw more? Boys and girls have different preferences, and many of these preferences have biological as well as cultural roots. (Indeed, are there any cultures where athletic prowess is more valued in women than in men?) And so we're right back on the African savannah, where men who liked to throw learned to throw well, and thus killed more game.

It seems that, even with a "cultural" explanation, you can't escape nature.