Human sacrifice is the act of killing one or more human beings, usually as an offering to a deity, as part of a religious ritual. Human sacrifice has been practiced in various cultures throughout history. Victims were typically ritually killed in a manner that was supposed to please or appease gods, spirits or the deceased, for example as a propitiatory offering, or as a retainer sacrifice when the King's servants are killed in order for them to continue to serve their master in the next life. Closely related practices found in some tribal societies are cannibalism and headhunting. By the Iron Age, with the associated developments in religion (the Axial Age), human sacrifice was becoming less common throughout the Old World, and came to be looked down upon as barbaric in pre-modern times (Classical Antiquity). In the New World, however, human sacrifice continued to be widespread to varying degrees until the European colonization of the Americas.