Medical innovations, India’s preference for male heirs, and China’s one-child policy have created an irreparable gender disparity in the world’s two biggest countries, where men outnumber women by 70 million. Many Chinese men have started buying brides from countries such as Russia, Vietnam and Cambodia. The imbalance has also led to an increase in prostitution, human trafficking and violence against women, but in some Indian villages, women have started fighting for equal rights.