Sure, there are cheaters among us, but overall, humans rank quite high among monogamous species, besting chimpanzees, black bears, African lions, and bottlenose dolphins, according to a study published Tuesday in Proceedings of the Royal Society B. Evolutionary anthropologist Mark Dyble of the University of Cambridge ranked 35 mammals by how monogamous they appear to be—based on how many pairs of siblings in a population share both parents versus only one. In a strictly monogamous species, nearly all siblings should be full siblings; in a more promiscuous one, half-siblings dominate, per the Wall Street Journal.
Evaluating humans by the metric is a bit tricky, given our use of birth control. Still, Dyble compiled sibling data from about 100 mostly contemporary human societies, plus ancient DNA from archaeological sites, finding 66% are full siblings. That's enough to make humans 7th on the list of most monogamous species, just behind Eurasian beavers. At the opposite end were Soay sheep, with just 0.6% of sibling pairs sharing both parents. The rate was 4% for chimps, black bears, and bottlenose dolphins, and 19% for African lions. The top 10, ranked by percentage of full sibling pairs, per the Guardian:
- California deermouse: 100%
- African wild dog: 85%
- Damaraland mole-rat: 79.5%
- Moustached Tamarin: 77.6%
- Ethiopian wolf: 76.5%
- Eurasian beaver: 72.9%
- Humans: 66%
- White-handed gibbon: 63.5%
- Meerkat: 59.9%
- Grey wolf: 46.2%
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