Are humans meant to stay faithful, or are we naturally inclined to have multiple partners? A new study from the University of Cambridge suggests that humans are mostly wired for monogamy, not promiscuity.
The research, led by evolutionary anthropologist Dr. Mark Dyble, looked at mating patterns across 35 different mammals. The study, published in 2025, also examined human relationships from ancient times to modern societies.
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To understand human behavior, researchers studied 103 human populations, using family records, archaeological findings, and even ancient burial sites. They compared how many siblings had the same parents versus different parents.
The result was simple: about two out of three siblings (66%) shared the same mother and father. According to Dr Dyble, this shows that humans mostly form long-term pair bonds.
When compared with animals, humans fell somewhere in the middle.
We are not as strictly loyal as the Eurasian beaver or the California deermouse, but we are far less promiscuous than chimpanzees, which mate with many partners.
The study challenges the idea that humans are “naturally unfaithful.”
Instead, it suggests that while humans are not perfectly monogamous, faithful, long-term relationships are more natural for us than casual mating.
