The police in China are collecting blood samples from men and boys from across the country to build a genetic map of its roughly 700 million males, giving the authorities a powerful new tool for their emerging high-tech surveillance state. They have swept across the country since late 2017 to collect enough samples to build a vast DNA database, according to a new study published on Wednesday by the Australian Strategic Policy Institute, a research organization, based on documents also reviewed by The New York Times. With this database, the authorities would be able to track down a man’s male...