Ann Laura Stoler has published a series of reviews of half-caste people and ethnic intermixing during the colonial era of human history. She states that colonial control was predicated on identifying who was white and who was native, which children could become citizens of the empire while who remained the subjects of the empire, who had hereditary rights of a progeny and who did not. This was debated by colonial administrators, then triggered regulations by the authorities. At the start of colonial empires, mostly males from Europe and then males of indentured laborers from India, China and southeast Asia went on these distant trips; in these early times, intermixing was accepted, approved and encouraged. Over time, differences were emphasised, and the colonial authorities proceeded to restrict, then disapprove and finally forbid sexual relationships between groups of people to maintain so-called purity of blood and limit inheritable rights.