Whale Rider

Just saw Whale Rider on DVD. It is set in a Maori tribe, where traditionally the first-born male child becomes the new chief. Pai is born into this line of heritage, but she is a girl. The rest of the movie is about her struggle to earn the love of her grandfather, who believes that everything went wrong the moment she was born.

After watching this movie, I have this question in my mind: Why is most part of the world dominated by male? How did that happen?