IN THE OAXACA Valley of Mexico, the archaeologists Joyce Marcus and Kent Flannery have gained a remarkable insight into the origin of religion.

During 15 years of excavation they have uncovered not some monumental temple but evidence of a critical transition in religious behavior. The record begins with a simple dancing floor, the arena for the communal religious dances held by hunter-gatherers in about 7,000 B.C. It moves to the ancestor-cult shrines that appeared after the beginning of corn-based agriculture around 1,500 B.C., and ends in A.D. 30 with the sophisticated, astronomically oriented temples of an early archaic state.

This and other research is pointing to a new perspective on religion, one that seeks to explain why religious behavior has occurred in societies at every stage of development and in every region of the world. Religion has the hallmarks of an evolved behavior, meaning that it exists because it was favored by natural selection. It is universal because it was wired into our neural circuitry before the ancestral human population dispersed from its African homeland.

For atheists, it is not a particularly welcome thought that religion evolved because it conferred essential benefits on early human societies and their successors. If religion is necessary for life, it is hard to portray it as useless.

For believers, it may seem threatening to think that the mind has been shaped to believe in gods, since the actual existence of the divine may then seem less likely.

But the evolutionary perspective on religion does not necessarily threaten the central prosition of either side. That religious behavior was favored by natural selection neither proves nor disproves the existence of gods. For believers, if one accepts that evolution has shaped the human body, why not the mind too? What evolution has done is to endow people with a genetic predisposition to learn the religion of their community, just as they are predisposed to learn its language. With both religion and language, it is culture, not genetics, that then supplies the content of what is learned.

It is easier to see from huntergatherer societies how religion may have conferred advantages in the struggle for survival. Their rituals emphasize not theology but intense communal dancing that may last through the night. The sustained rhythmic movement induces strong feelings of exaltation and emotional commitment to the group. Rituals also resolve quarrels and patch up the social fabric.

The ancestral human population of 50,000 years ago would have lived in small, egalitarian groups without chiefs or headmen. Religion served them as an invisible government. It bound people together, committing them to put their community’s needs ahead of their own self-interest. For fear of divine punishment, people followed rules of self-restraint toward members of the community. Religion emboldened them to give their lives in battle against outsiders. Groups fortified by religious belief would have prevailed over those that lacked it, and genes that prompted the mind toward ritual would have become universal.

In natural selection, it is genes that enable their owners to leave more surviving progeny that become more common. The idea that natural selection can favor groups, instead of acting directly on individuals, is highly controversial. Though Darwin proposed the idea, the traditional view among biologists is that selection on individuals would stamp out altruistic behavior far faster than group-level selection could favor it.

But group selection has recently gained two powerful champions, the biologists David Sloan Wilson and Edward O. Wilson, who argued that two special circumstances in recent human evolution would have given group selection much more of an edge than usual. One is the highly egalitarian nature of huntergatherer societies, which makes everyone behave alike and gives individual altruists a better chance of passing on their genes. The other is intense warfare between groups, which enhances group-level selection in favor of community-benefiting behaviors such as altruism and religion.

A propensity to learn the religion of one’s community became so firmly implanted in the human neural circuitry, according to this new view, that religion was retained when hunter-gatherers, starting from 15,000 years ago, began to settle in fixed communities. In the larger, hierarchical societies made possible by settled living, rulers co-opted religion as their source of authority.

Religion was also harnessed to tasks like agriculture, which in the first societies to practice it required unaccustomed forms of labor and organization. Religion is often blamed for its spectacular excesses, whether in promoting persecution or warfare, but gets less credit for its staple function of patching up the moral fabric of society. But perhaps it doesn’t deserve either blame or credit. If religion is seen as a means of generating social cohesion, it is a society and its leaders that put that cohesion to good or bad ends.

DAVID SILVERMAN/GETTY IMAGES; BELOW, MEREDITH KOHUT FOR THE NEW YORK TIMES / Religion has been found at all stages of societal development. Above, a baptism in Brazil. A Maria Lionza ritual in Venezuela.



WATHIQ KHUZAIE/GETTY IMAGES / As primitive groups fortified by faith prevailed over others, religion was favored by natural selection. Iraqi men and a boy praying.