Separate but equal still alive in Hollywood

My wife and I caught about ten minutes of the Golden Globe Awards last night, and I came away wondering:

Why are the best acting awards divided along gender lines? 

While there are competitive endeavors in which the division of the sexes seems reasonable (basketball, soccer, and similar athletic events, at least for now), there is no discernable reason why actors and actresses cannot compete against one another, and I can't imagine why they would not want to vie for the same award.

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