I think that the root cause is not the gender as it is the perceived weakness and the way many people want to feel superior by mistreating others. Also the mental baggage societies carry, where maybe few thousand years ago the families with a son could do better that a family with a daughter, since heavy work was the main way to get food. That got so ingrained in people's minds and society as a whole, that many still just accept it as common knowledge and don't question anything. I guess that's more apparent in developing countries, but I have noticed that it isn't absent in developed countries either. People really need to start thinking for themselves. I think it's getting better, or maybe its just my wishful thinking. Common sence may work fine locally(at the time), but its doesn't work at all in the long run.