Monogamy: Rare in Nature, Still Common for Humans – New Study

Despite popular portrayals in fiction and everyday conversation, lifelong monogamy remains the dominant relationship style globally. While the idea of multiple partners – whether polygyny, where a man has multiple wives, or polyandry, where a woman has multiple husbands – captures the imagination, it’s practiced by a surprisingly small percentage of the world’s population: just 2%. Even infidelity, often described as a hidden form of polygamy, is relatively uncommon, with estimates suggesting that the percentage of children raised believing the wrong man is their father doesn’t exceed 1% – a figure that hasn’t significantly changed even with the widespread availability of contraception.

	Polyandry is a form of polygamy where a woman has more than one husband. It is practiced in regions with harsh living conditions, where a single man may struggle to adequately support a wife. For example, in Tibet, up to three brothers may marry the same woman. A video from National Geographic explores one such union.
Kredit: Bob King, Wikipedia.	The image on the left depicts the five Pandava brothers with their shared wife, Draupadi. They are heroes from the ancient Indian epic Mahabharata, dating back to the late 2nd millennium BC. Credit: Bob King, Wikipedia, CCBY 2.0.
Kredit: Wikipedie, Volné dílo.	Polygyny is a form of polygamy where a man has multiple wives and was common in ancient Israelite culture. It is mentioned in the Bible, particularly in the Old Testament. The image on the left shows Elkanah and his two wives. Islam also permits polygamy for men, though the Prophet Muhammad reportedly encouraged limiting oneself to a maximum of four wives, ensuring equal fulfillment of obligations to each.

The enduring prevalence of monogamy may be rooted in evolutionary biology. Research suggests that humans have a strong evolutionary basis for pairing, as raising a human child is a lengthy and demanding process requiring the involvement of both parents. A secure paternal bond, in turn, is more likely when a father is certain of his paternity.

This isn’t a phenomenon unique to humans. A comprehensive overview of monogamous and polygamous relationships is offered by Mark Dyble of the University of Cambridge in a study published in the journal Proceedings of the Royal Society B.

Monogamy’s Leading League

Dyble measured the degree of monogamy through genetic analysis, differentiating between siblings who share both parents and those who share only one. He analyzed data from 103 different human populations, including prehistoric ones, encompassing nearly 200,000 sibling pairs. He also examined data from over 61,000 sibling pairs across 34 mammal species.

It’s important to note that shared parentage doesn’t always equate to polygamy. The loss of a partner and subsequent remarriage can result in half-siblings, a pattern known as serial monogamy.

Among humans, approximately 70% of siblings share both parents, placing us among strict monogamists. This is comparable to species like surikats (59% shared parentage), beavers (73%), and African wild dogs (85%). Among primates, only gibbons (63%) and white-whiskered tamarins (78%) exhibit similar levels of shared parentage. However, humans clearly stand out when compared to great apes. Mountain gorillas have only 6% shared parentage, while chimpanzees have 4%. Even dolphins exhibit a high degree of promiscuity, with only 4% of siblings sharing both parents. Macaques, with just 1% shared parentage, represent the lowest level of monogamy in the study.

Mark Dyble. Autor studie. Kredit: University of Cambridge.

“There’s a monogamous premier league, and humans have a firm place in it,” says Mark Dyble. “Most mammals are substantially more promiscuous. The finding that we match clear monogamists in the animal kingdom only reinforces that monogamy is genuinely our main type of partnership.”

Why Are We Closest to the Patagonian Mara?

Humanity’s position in the monogamous premier league appears to be the result of a dramatic shift that occurred after humans evolved as a distinct species. Great apes show no inclination towards monogamy. According to Dyble, similar transitions from polygamous to monogamous lifestyles are relatively rare. He cites wolves and foxes, which exhibit significant levels of monogamy (46% and 45% respectively), despite their ancestors not living in permanent pairs. In Africa, certain canids demonstrate even higher rates of monogamy, such as the Ethiopian wolf (76%).

Extreme cases include the California ground squirrel, where 100% of siblings share both parents, and the primitive Soay sheep breed on the Scottish island of Soay, where only 0.6% of siblings share both parents (link to Soay sheep information).

However, Dyble identifies a key difference between animal monogamists and humans: “Almost all monogamous mammals live either in families consisting of a single parental pair and their offspring or in groups where only one female is reproductively active. Humans, however, live in groups where multiple women have children.”

Dyble found a comparable creature in the animal kingdom. The Patagonian mara, a South American rodent, lives in a burrow system inhabited by several permanent pairs. As the saying goes, there’s nothing new under the sun.

Source:

Dyble M.: Human monogamy in mammalian context. Proceedings of the Royal Society B, (2025) 292 (2060): 20252163.

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