Monogamous relationships among certain primates can help reproduction, promote peaceful living and lead to better care of infants, new research finds.

The study, published in PLoS ONE, focused on intense relationships that occur among nocturnal owl monkeys, but close couples also form in titi monkey, gibbon, marmoset, tamarin monkey and, of course, human populations.

The important factor is not just monogamy, but “pair bonding.”

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“By pair bonding we mean a strong, enduring and relatively exclusive relationship,” lead author Eduardo Fernandez-Duque told Discovery News, adding that such bonding is also associated with reproduction. The relationship “may last forever, or it may be relatively long, but not forever.”

Fernandez-Duque, an associate professor in the University of Pennsylvania’s Department of Anthropology, and co-author Maren Huck amassed data from 16 years of observing 18 owl monkey groups — 154 animals living in a portion of Argentina’s Chaco region.

The researchers closely observed monkey pairs and documented their relationship dynamics along with reproductive rates. They found that owl monkeys with one partner produced 25 percent more offspring per decade than those with two or more partners.

“What we’re showing is that if you manage to stay with the same partner, you produce more infants than if you’re forced to change partners,” Fernandez-Duque said.

It’s not yet clear why this happens, but one theory is that the two individuals — as with most human couples — take time to assess one another before reproducing. Owl monkey fathers, like good human dads, “are immensely committed to providing care for their infants,” he said. Moms of this species are also very devoted to their offspring.

Conservation International/Stephen Nash

Monogamy may lead to improved infant care, since males are more certain about paternity, which typically results in greater bonding. Females then benefit too, since the male’s support lessens the burden of pregnancy and lactation.

The findings could help to explain how pair bonding arose in non-human primates and in our species.

To this day, not all human societies are monogamous, but “anthropologists still do believe that the pair bond may have been critical to the evolution of human societies,” Fernandez-Duque said. “In humans, the pair bond may be important for committing the partners to share space, time, labor, infant care and provisioning.”

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Such relationships also seem to promote peace among larger groups. Titi monkeys, for example, are monogamous primates that are often described as living relatively peaceful lives. “Make love not war” can also benefit humans.

“Call it love, call it friendship, call it marriage," Fernandez-Duque said. "There is something in our biology that leads to this enduring, emotional bond between two individuals that is widespread among human societies.”

Agustín Fuentes, a University of Notre Dame professor of Anthropology, told Discovery News that the new research is “groundbreaking.”

“This report is particularly important because it demonstrates the value of the pair bonds in actual evolutionary relevant terms — reproduction. Being in the same pair, and having a robust pair bond is core to being a successful owl monkey.”

Fuentes added, “Monogamy is extremely rare as a social system in mammals, and it is through intensive and well-crafted work such as this that we are finally starting to see how such systems actually operate.”