Nature wants us to reproduce, so how come celibacy evolved?
Enlarge / Nature wants us to reproduce, so how come celibacy evolved?

Why would anyone join an institution that required them to be celibate? The evolution that shaped us is based on reproduction. Many religious institutions need this. Celibacy could have evolved in the first place, according to anthropologists.

It has been suggested that practices that are costly to individuals, such as never having children, can still emerge when people blindly conform to norms that benefit a group. Some argue that people create religious institutions because they serve their own selfish or family interests, and reject those who don't.

The new study was published in the Royal Society Proceedings B and was conducted in Western China.

Some Tibetan families used to send their sons to the local monastery to become monks. Up to one in seven boys become monks. Families often cite religious reasons for having a monk in the family. Economic and reproductive considerations were involved.

We interviewed 530 households in 21 villages in the eastern part of the Tibetan plateau with the help of our Chinese partners. We gathered information about each person's family history and if any of them were monks.

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The Amdo Tibetans who live in these villages are patriarchal and raise herds of animals. The wealth is passed down to the males.

Men with a brother who was a monk had more money and owned more yaks. There was nothing for sisters of monks. Brothers are competing for resources and land. Parents put an end to the conflict by sending their son to the monastery. Second or later-born sons are more likely to inherit the household than first born sons.

Men with a monk brother had more children than men with non-celibate brothers, and their wives tended to have children later in life. As their non-celibate sons faced less or no competition with their brothers, grandparents with a monk son had more Grandchildren. It is in line with a parent's reproductive interests to send a son to the monastery.

A mathematical model of celibacy

Celibacy can be evolved by natural selection. We studied the consequences of becoming a monk on a man's evolutionary fitness and built a mathematical model of the evolution of celibacy. The case where the decision to send a boy to a monastery is made by his parents is similar to the case where a boy makes his own decision.

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Men are less likely to marry to women in the village if monks remain single. One of the men in the village might benefit from becoming a monk, but the monk's decision doesn't further his genetic fitness Celibacy shouldn't change.

If a man has a brother who is a monk, he will be more competitive on the marriage market. Natural selection allows religious celibacy to evolve because a monk is helping his brothers have more children. It isn't very beneficial if the choice to become a monk is down to the boy himself

Celibacy becomes more common if the parents decide it should happen. If there is a benefit for the others, parents will send a child to the monastery. The fact that boys were sent to the monastery at a young age with a lot of celebration and faced if they later abandoned their role suggests a cultural practice shaped by parental interests.

The evolution of parental favoritism in other cultural contexts could be clarified by this model. Female celibates are rare in patriarchal societies such as Tibet, but are more common in societies where women are in greater competition with each other.

New research is being developed to understand why monks and nuns are in high demand in certain parts of the world.

New ideas can lead to the creation of new institutions if people conform to a new standard. People's reproductive and economic decisions can affect institutions.

The Conversation has a license to republish this article. The original article is worth a read.