Research published by British evolutionary anthropologist Mark Deepley in the Proceedings of the Royal Society shows that humans rank seventh among mammals most loyal to their partners, behind beavers and tamarins.
Debley based his classification on archaeological and ethnographic data from over 100 human settlements, as well as information from other animal research. Similar studies are rarely conducted among animals, limiting the available data to only 34 mammal species out of more than 6,000 known species.
The degree of fidelity was determined by calculating the percentage of full siblings in the populations studied. In the populations included in the study, this percentage ranged from 26% in a Neolithic group in Britain to 100% in a group from the same period in northern France, with an average of 66% for humans.
California rodents (hamsters) topped the rankings with 100% , with African wild dogs ( 85% ) and Nax moles ( 79.5% ) rounding out the top three, while humans scored 66% , ahead of white gibbons ( 63.5% ) but behind beavers ( 72.9% ).
Debleby noted that the study supports the "monogamy hypothesis ," which posits that animal populations achieve a high level of cooperation when reproduction occurs in monogamous relationships and produces whole-related offspring. He added that even a slight deviation from monogamy leads to a sharp decrease in the number of whole-related children; for example, a 25% increase in pregnancies outside of marriage reduces whole-related offspring to 40% . Debleby believes that monogamy may be a key human trait that has helped build large societies by understanding the degree of kinship among their members.
