People’s marriage relationships can look very different from culture to culture. But from a biological point of view, it is generally accepted that people tend to choose a marriage partner for life, or for a very long time, at least. Among mammals, there are other species in which the male and the female keep loyalty to each other for more or less long. (Although there are few such animals among animals, only 3-5% of species, while monogamous birds have about 90%.) And when researchers want to know the neurobiological mechanisms of monogamy, they take some easy-to-handle animal as a model and experiment with him.
Many experiments are carried out here on yellow-bellied voles. Compared to polygamous related species, such as meadow voles, you can see the difference in brain neurochemistry. For example, receptors for the neurotransmitter hormones oxytocin and vasopressin are distributed differently in monogamous voles than in polygamous ones. Largely due to voles, oxytocin is often called the hormone of love and fidelity. Although it is usually said in such cases that although rodents and primates belong to mammals, the brains of both are still markedly different. And that the results obtained in rodents must be extended with caution to primates.
Employees Duke University have clearly shown that this is not an empty reservation. The researchers compared the neurochemistry of the brain in seven species of lemurs. Among them were mongoose and red-bellied lemurs – monogamous species in which a male and a female form a pair for many years, growing offspring together and protecting the territory. The other five species were polygamous. For the experiments, they took animals that died for natural reasons. In monogamous and polygamous lemurs, the distribution of receptors for vasopressin and oxytocin in the brain was compared – not only among themselves, but also with voles and with other monkeys.
It turned out that the location and density of these receptors in lemurs is different from what can be seen in voles and other primates. That is, “neurotransmitters of love and fidelity” act on other neural circuits and nerve centers. Moreover, there were differences even between different species of lemurs. That is, they did not have some kind of constant neural structure responsible for the formation of a mating pair, which would be in monogamous species and which would not be in polygamous species. In voles, this kind of neural structure can be found, but not in lemurs. Research results published in Scientific Reports.
Strictly speaking, the data obtained only report on the features of the distribution of receptors for certain neurotransmitters. In the future, the authors of the work want to experiment with living lemurs, blocking their oxytocin receptors, in order to see what happens with the lemurian “relationship”. But now we can say that since the receptors are distributed the way they are distributed, then, probably, all love and loyalty should not be reduced to oxytocin-vasopressin, and it is not worth looking for a common neural “marriage ring”. Still, marriage behavior is quite complex. It would be natural if it was based on different structures, and if in the brain of different groups of animals this problem was solved in different ways.
And even if you come from the other side and take a closer look at only one oxytocin: on the one hand, there are experiments with people when it really increased emotional attachment to a partner, on the other, the same oxytocin is quite capable of causing aggression. Which once again speaks of how difficult everything is in the brain.
Source: Автономная некоммерческая организация "Редакция журнала «Наука и жизнь»" by www.nkj.ru.
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