Philosopher Daniel Dennett states the problem clearly: “The ultimate measure of evolutionary value is fitness—the capacity to replicate more successfully than the competition does.” Yet on the face of it religion seems useless from an evolutionary point of view. It costs time and money, and it induces its members to make sacrifices that undermine their well-being for the benefit of others, who are sometimes total strangers.

Religious people build cathedrals and pyramids that have very little utility except as houses of worship and burial. The ancient Hebrews sacrificed their fattest calves to Yahweh, and even today people slaughter goats and chickens on altars. Religious people sometimes forgo certain foods—the cow is holy to the Hindus, and the pig unholy to the Muslims. Christians give tithes and financial offerings in church. The Jews keep holy the Sabbath, as Christians keep Sunday for church. Religious people recite prayers and go on pilgrimages. Some become missionaries or devote their lives to serving others. Some are even willing to die for their religious beliefs.