Staying loyal to your family is more profitable

Scientists in a study of night monkeys came to the conclusion that changing a regular partner to a more attractive newcomer reduces the reproductive rate of the family by a full quarter.

Indeed, the amazing flexibility of sexual and sexual relationships is one of the unique features of our species. Almost all other animals have a certain established type of such relationships, a social organization closely related to it, and even a body structure.

Polygynous species are distinguished by noticeable sexual dimorphism (their males and females differ sharply from each other), strong competition for mates, and extremely aggressive behavior towards rivals. The numbers of males and females in their populations are not equal, and the dominant sex wages a continuous struggle for individuals suitable for mating. Monogamy is usually associated with approximately equal numbers of females and males, sexual monomorphism, and less aggressive competition for mating opportunities. Although anything can happen.

Night monkeys , for example, are one of the rather rare cases of monogamy among primates, in which males and females form permanent married couples to bear and raise children together. And the more stable the couple, the better it does. These conclusions were reached by American researchers led by Professor Eduardo Fernandez-Duque , who, since 1997, observed the life of 18 groups of night monkeys in the natural forests of Argentina.

Photo: Reuters

These communities seemed like something of a family idyll, but in 2008, researchers reported that they were often home to far from harmless single macho men of both sexes. Such individuals, not having their own partners, easily come into conflict with the “family” ones and in some cases even expel them, taking up the vacant space.

In their work, the authors show that such scenarios occur quite often among nocturnal monkeys: over 16 years of observations, out of 145 individuals, there were 27 cases of change of the “family” female and 23 cases of change of male. We can say that during this time a third of the marriages fell apart - what an idyll that is!.. And all this was accompanied by very dramatic clashes, some of which even ended fatally for the vanquished.

However, the winners are not able to fully enjoy their victory. Scientists have noticed that such insidious behavior significantly reduces the productivity of the new family. Over the course of 10 years, it produces, as a rule, 25% fewer offspring than families established in sickness and health, in sorrow and joy.

The authors explain this effect by a decrease in the fertility of the partner remaining in the family and a long period of “grinding in”, during which newly-made lovers get used to each other’s character and habits. Everything is like people.