New research places humans firmly within the top tier of monogamous mammals, despite cultural variations in mating practices. A study led by Cambridge anthropologist Mark Dyble assessed reproductive patterns across species by analyzing sibling relationships – specifically, the proportion of full versus half-siblings. The results show that humans rank seventh out of 35 species, with roughly 66% of offspring sharing the same two biological parents.
The ‘Monogamy Scale’ Explained
Dyble’s method is a novel approach to measuring monogamy. Traditional assessments often rely on behavioral observation, which can be subjective. Instead, this study uses genetic data from archaeological samples and ethnographic records to determine the frequency of full sibling relationships. This provides a more objective metric for comparing monogamous tendencies across species.
The study compared data from ancient human remains (from Europe and Asia) to genetic records of 34 other mammals. The most striking finding is that human monogamy rates overlap significantly with other socially monogamous species like meerkats and Eurasian beavers.
Human Behavior vs. Other Mammals
Humans scored higher than many primate relatives, including gorillas (6% full sibling rate) and chimpanzees (4%), which exhibit highly promiscuous mating behaviors. Even dolphins share similar levels of non-monogamy with chimpanzees. The California deermouse topped the list with 100% full siblings, while the African wild dog (85%) and Damaraland mole rat (79.5%) also ranked high.
Dyble notes that human monogamy likely evolved from more flexible mating systems, making it an unusual transition in the mammalian world. This suggests a unique combination of social and genetic factors drove the shift towards long-term partnerships.
The Limits of Genetic Data
The study acknowledges the limitations of relying solely on genetic data. Birth control, cultural norms, and unrecorded affairs all influence the accuracy of these metrics. Genealogical studies also depend on the information individuals choose to share. The research doesn’t account for non-procreative encounters or polygamous relationships where multiple partners are openly acknowledged.
However, the overall pattern suggests that humans are more monogamous than most mammals, even when factoring in cultural variability. The dominance of pair-bonding for raising offspring seems to be a defining feature of our species.
The study’s full ranking demonstrates the diversity of mating strategies in the animal kingdom. The results underscore the evolutionary forces that shape monogamy, and where humans fit in the broader context of the natural world.
