How Monogamous Are Humans? Cambridge Study Ranks Us Among Mammals

New research from the University of Cambridge compares how often animals produce full siblings versus half-siblings to estimate how monogamous different species are. The study finds humans are substantially more monogamous than our closest primate relatives, though not as strictly monogamous as some other mammals such as beavers.

Study Design and Data

Led by evolutionary anthropologist Mark Dyble, the research team combined genetic sibling data from multiple mammal species with a computational model to generate monogamy ratings. For humans the analysis drew on genetic evidence from archaeological sites and ethnographic information covering 94 distinct societies, capturing wide cultural variation in mating and marriage practices. The findings were published in Proceedings of the Royal Society B.

Key Findings

Monogamy Ratings (Selected): Beavers 72%, Humans 66% (average), Meerkats 60%. At the low end, dolphins and chimpanzees scored 4% and mountain gorillas 6%.

The authors place beavers, humans and meerkats in a so-called "premier league" of species that most commonly form long-term pair bonds. Across the dataset of species the authors classified as socially monogamous, humans ranked seventh of eleven.

“This is not the first study to use sibling proportions as a measure of monogamy, but it is the first to compare the rates in humans to other mammal species,” Dyble told CNN. He also noted that even the human societies with the lowest proportions of full siblings (about 26%) still exceed the highest value recorded for any clearly non-monogamous mammal in the dataset (22%).

Isabel Smallegange of Newcastle University, who was not involved in the research, described the method as clever and called the headline finding striking: humans are considerably more monogamous than many close relatives. She also emphasized that human social success likely depends on a mix of pair-bonding, kin networks and cultural institutions rather than a single mating strategy.

Implications

The study strengthens the view that long-term pair bonding is a dominant mating pattern in humans at the species level, even though cultural practices vary widely. Using sibling proportions as a cross-species metric provides a new comparative lens on mating systems and highlights a clear separation between species labeled socially monogamous and those that are not.

Publication: Proceedings of the Royal Society B. Reporting contribution by Taylor Nicioli.