Humans spend an absurd amount of time debating monogamy. We argue about whether it’s natural, cultural, outdated, or aspirational, usually while pretending animals have it all figured out. An anthropologist just complicated that story by ranking humans alongside other mammals and seeing who actually stays with the same reproductive partner over time.
Mark Dyble, an evolutionary anthropologist at the University of Cambridge, built what amounts to a mammal monogamy scale. Instead of relying on labels like “pair-bonded” or “socially monogamous,” he used something harder to spin. Siblings. Specifically, how often siblings share the same two parents. Using that measure, humans placed seventh among the mammals he studied.
“There is a premier league of monogamy, in which humans sit comfortably, while the vast majority of other mammals take a far more promiscuous approach to mating,” Dyble said in a statement.
Across the human societies included in the research, about 66 percent of siblings shared the same parents. That number puts humans in the same range as animals commonly described as socially monogamous, including Eurasian beavers and meerkats. It also places us far above several of our closest evolutionary relatives. Mountain gorillas came in at just over six percent. Chimpanzees landed around four percent, tied with bottlenose dolphins.
Dyble pulled the human data from two sources. One came from ancient DNA recovered at archaeological sites across Europe and Asia, mostly dating to the Neolithic and Bronze Age. The other relied on family trees compiled by ethnographers working with 94 pre-industrial societies. For other mammals, he used existing genetic studies detailed enough to show kinship structure and reproductive skew.
Humans Are Less Monogamous Than Beavers But More Monogamous Than Sheep
At the top of the list sat the California deermouse, which showed a perfect record of 100 percent full siblings. At the bottom were macaques, seals, and sheep, where shared parentage among siblings was rare. Humans landed in the upper tier, closer to wolves than primates.
“The finding that human rates of full siblings overlap with the range seen in socially monogamous mammals lends further weight to the view that monogamy is the dominant mating pattern for our species,” Dyble said.
The approach has limits. DNA only reflects relationships that produced children. Human reproductive behavior is shaped by contraception, social rules, and long sequences of partnerships that don’t always leave genetic traces. Dyble acknowledged that gap, noting that humans maintain “a range of partnerships that create conditions for a mix of full and half-siblings with strong parental investment.”
This ranking won’t tell anyone how to structure a relationship. It does suggest that, biologically speaking, humans behave more predictably than our cultural narratives imply. On a mammal scale, we cluster closer to beavers than chimpanzees, which is information people can sit with as they like.
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