Powerful men use shaken bones or ground-up herbs or sacrifice an animal to bring luck.

ECONOMIST: The king is still in charge

Half the Olympic program, on the other hand, was given over to religious ritual: processions, hymn-singing, incense-burning, gory animal sacrifice and strange incantations by exotically attired priests.

WSJ: The Ancient Olympics: Mud, Sex, Hymns...Sports Too

Yet examples of self-sacrifice abound in animal societies.

ECONOMIST: Bill Hamilton

Second, the animal bones indicate that the burial was accompanied by a sacrifice.

NPR: Karen Armstrong: Myths and the Modern World

As an antidote to this picture, he offers plenty of evidence of apparently selfless sacrifice, unforced sympathy, co-operation and even a keen sense of fairness in our closest animal relatives, who evolved to reap the benefits of mutual aid.

ECONOMIST: The evolution of empathy