Human sacrifice is defined as the ritualized, religiously motivated killing of a human being. It is no longer sanctioned by any state, but it was once practiced by societies across the globe. Chiefs and priests routinely strangled, bludgeoned, drowned, and burned their victims to death in order to please various ancestors or deities. Though human sacrifice is a thing of the past, many believe that understanding what motivated it is still relevant because other manifestations of extreme inequality do persist—slavery, for example. Seshat is a database that covers more than 400 societies that existed across the globe over the last 10,000 years. Seshat’s founders argue that beyond around 100,000 people, human sacrifice becomes a destabilizing force. They say at these thresholds human sacrifice became a parasitic practice—an attempt, often by military heroes who had transformed themselves into “god-kings,” to seize and maintain power, to the detriment of social cohesion. According to Peter Turchin, professor of ecology and evolutionary biology and one of Seshat’s founders, this mattered because the survival of historical societies often depended on their military prowess. Those that were less united and hence weaker on the battlefield may have found themselves destroyed by, or absorbed into, militarily superior ones that had rejected human sacrifice, having found better ways of promoting social cohesion. The Spanish conquest of the Inca could be considered an example of the survival of the fittest society, in this sense.