In Japan, it was said that sacrificing a woman at a rushing river would placate the spirit who lived there, allowing for the construction of bridges and the safe passage of boats. In Greek myth, the warrior king Agamemnon decides to kill his own daughter in exchange for a favorable wind on the way to Troy. The Egyptians buried some of their pharaohs with dozens of servants when they died, ensuring that their needs would still be met in the afterlife. Bodies found entombed in bogs across Europe may have been slain as gifts for higher powers. The great civilizations of Mesoamerica killed people, smashed food and sank treasure to pay their debts to their gods.
    In much of the pre-modern world, ritual sacrifice was framed as necessary for the good of the society at large—the only way to guarantee, say, a plentiful harvest or success in war. But the priests and rulers who sanctioned such killings may have had another motive, a new study suggests. An analysis of more than seven dozen Austronesian cultures revealed that the practice of human sacrifices tended to make societies increasingly less egalitarian and eventually gave rise to strict, inherited class systems. In other words, ritual killings helped keep the powerful in power and everyone else in check.
    That finding might seem intuitive—societies in which some members are habitually killed probably value certain lives over others—but it has broader implications, the researchers said in the journal <em>Nature</em>. The link between the sacrifices and social hierarchies seemed to transcend those differences. The victims were almost always of low social status, and the more stratified the culture was, the more prevalent ritual killings were likely to be.
    This finding supports the "social control hypothesis" of human sacrifice, the researchers said. This idea suggests that ritual killings are a way to terrorize people into submission, allowing the religious and political leaders (and in many cultures, those were one and the same) who ordered the killings to consolidate power unopposed.
    "I think it's absolutely an important project," University of British Columbia psychologist Joseph Henrich told the <em>New Scientist</em>. "Sacrifice does seem to have been performed in societies all around the world."
    But he urged some skepticism about the study's broad conclusions. Though human sacrifice may have been correlated with stratification in the Austronesian societies, Henrich was dubious of the phylogenetic analysis the researchers used to prove that the relationship was casual. That tool assumes that social strata and religious rituals are passed down and evolve through generations in the same manner as languages.  It can be inferred from Paragraph 1 that ______.