Elaborate ritual killings such as being crushed under a newly built canoe and decapitation after being rolled off a house laid the foundations of class-based structures in modern societies, a new study of Austronesian cultures suggests. — http://www.abc.net.au/news/2016-04-05/human-sacrifice-may-have-helped-build-social-class-structures/7297460
The source article is Ritual Human Sacrifice Promoted and Sustained the Evolution of Stratified Societies in Nature magazine. I see from its first paragraph that it uses our old favourite, Bayesian analysis.
Egalitarian societies are a good thing.
Don’t we see even in class societies that no longer practice human sacrifice the upper classes expending the blood of the lower classes in other ways — all buttressed by noble and praiseworthy ideologies, of course.