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Wife Swapping in the Stone Age

Wife sharing in early human societies was more common than we used to think.

Anthropologists are all too familiar with the violence and bloodshed triggered by marital infidelity. Now they are coming to terms with a more mysterious phenomenon—consensual wife sharing. If men fly into homicidal rages when their wife cheats on them, why would they encourage another man to sleep with her?

Stone Age Polyandry

Formal polyandry in which two or more men share a spouse is defined by a marriage contract. Reasons for such marriages include an excess of males in the population (1). The thinking is that two men (often two brothers) have a better chance of paternity if they share a wife than if they remain unmarried. Exactly the same logic applies to polyandry in other species, as illustrated by birds such as jacanas where a female is typically bonded to two or more males that nest in her territory.

In agricultural societies of Tibet and elsewhere, polyandry is entered into as one method of preventing family estates from being split up. Anthropologists are finding that polyandrous marriage is much more common than previously supposed. They are also finding polyandry in many hunter-gatherer societies where it was presumed to be absent (1).

This is significant because it suggests that this form of marriage has been around long enough to affect the evolution of pair bonding in our species. One possible implication is the remarkable flexibility of women's sexual behavior in the sense that they can accept multiple partners more easily than is true of many pair-bonded species (whether primates or non-primates). Men are generally not very comfortable with polyandrous marriage due to sexual jealousy, uncertain paternity, and conflict over paternal investment in children.

In addition to formal polyandry, many hunter-gatherer societies have informal polyandry that is superficially similar to wife swapping, or swinging, in modern societies. Wife swapping could be described as husband-swapping but that term never took off. The term seems demeaning to women because it implies that they are the property of their husbands. Yet there are two reasons that it rings true. First, sexual intercourse is widely considered a service that women provide to men, rather than vice versa (2). Second, in many societies studied by anthropologists, wives are traded like property and treated like possessions, painful though this is to modern sensibilities.

Informal Polyandry

In developed countries, polyandrous marriage is not recognized and presumably does not occur. Informal polyandry, or wife-swapping, became fairly common in California in the 1970s when widespread use of contraceptives took the paternity problem off the table (2). Swinging was possibly motivated by a masculine desire for sexual variety in an environment that did not threaten marital stability as much as having affairs. Symons points to the irony that women actually derived much more sexual pleasure from such events (frequently by having sex with other women), whereas men quickly became fatigued. Much of the swinging disappeared due to the HIV/AIDS epidemic.

Informal polyandry is a feature of some hunter-gatherer societies, such as the Inuit of northern North America, or the Yanomamo of the Orinoco river basin in South America.

Among the Inuit, a male guest might be invited to sleep with the lady of the igloo (2). This custom might seem to take being a good host to a dangerous extreme but accepting the offer incurs an obligation to reciprocate by sharing one's own spouse's sexual favors.

There is an even more onerous potential cost because in sleeping with his host's wife, the guest incurs responsibility for her children in the event that the host dies early (1). This helps to explain a pattern whereby societies practicing informal polyandry have high male mortality.

As marketers have long known, there is no such thing as an absolutely free gift in business because the gift incurs psychological obligations in the recipient. The same applies to Stone Age wife swapping, it seems.


1. Starkweather, K. E., and Hames, R. (2012). A survey of non-classical polyandry. Human Nature, 23, 149-172.

2. Symons, D. (1979). The evolution of human sexuality. New York: Oxford University Press.

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