The lesson of lemurs on love

Not all monogamous mammals are linked by love in the same way: the brains of the various species interact differently with the hormones oxytocin and vasopressin. Here's what we discovered in the lemurs

(photo: David Haring, Duke Lemur Center) Valentine's Day, the party of lovers, the day when looking into the eyes of the right person you imagine being with her, and only her, forever. And like us humans, other mammal species (quite a few to tell the truth, only 3-5% of the 6,500 known) form pairs that last a lifetime. A question of chemistry, the scientists say, even if it seems not the same for everyone.



A team from Duke University, in fact, has studied the brain circuits of monogamous and promiscuous species of lemurs of Madagascar, our distant cousins, discovering that the chemical language of love is very different in the mammalian kingdom.

The secret of lasting love

Precisely because monogamy is such a characteristic rare for mammals, scientists for a long time thought that its biological basis was the same in all species with this inclination.

In thirty years of research on some rodents, voles have accumulated evidence on the role played by two hormones, oxytocin and vasopressin, in the brain: it would be their action during courtship that determines the duration of the bond between partners. In fact, monogamous voles species possess more receptors for these two hormones on brain cells than non-monogamous voles species.

That is also the case for other mammals that form lifelong pairs, beings humans included?

Monogamy is still a mystery

To find out, the team of Christine Drea of ​​Duke University carried out a study on seven species of lemurs from Madagascar, both monogamous and promiscuous. An attempt to go a step further to solve the enigma of monogamy in humans, because, although these animals are our most distant primate relatives, they are genetically closer to us than voles.

Researchers used an imaging technique called autoradiography to map oxytocin and vasopressin receptors in the brains of some lemurs (who died of natural causes within the Duke Lemur Center).

What emerged is that the distribution of oxytocin and vasopressin receptors in lemurs is very different than in voles, which scientists say means that hormones don't have the same effect from one species to another because they interact with different areas of the brain.

Limiting the analysis only to lemur species, then, the researchers were amazed to find that there was no significant difference in the distribution and density of hormone receptors between monogamous and promiscuous species of lemurs.

Morality? Love is a complicated business, and one that lasts over time perhaps even longer. It is probable, the researchers conclude, that there is no chemical formula of monogamy that is the same in all species and that more chemicals together with ethological factors contribute to the establishment of a similar relationship between the partners.