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The DNA of the bad guy
In evolution, everything is pretty simple and cynical. If some genes increase the likelihood of leaving a lot of offspring, then they will spread with each generation in the population wider and wider. If genes, on the contrary, reduce the probability of successful reproduction, they will eventually grow less and less common. This principle applies not only to banal anatomy and physiology, but also to behavior. Any decisions we take with the brain, it consists of cells, cells - from molecules, the composition of molecules is determined by genes. If some genes increase the likelihood of making a decision useful for survival of the offspring, then their bearer will have more children who will inherit the same valuable genes, will also behave correctly, and so on.
The good news is that in the case of breeding there is no one right answer. If a man has genes that increase his desire for casual relationships, then it is certainly good - perhaps some of the tempted women give birth to his children. But if a man instead has genes that increase the likelihood of developing a strong affection for his only woman, and a tendency to take care of the born children, this can be even better, because in such a situation, the appearance of children and their further survival is much easier to control. If the smoothie is very lucky with beauty, wealth, charm and independent lovers, he may have ten children. But, if he is lucky a little less, he can not leave a single one. But a careful family man, with minimal effort, will find a woman willing to give birth to him four, and at the same time all four will survive to adulthood and will be successful and prosperous, because they were well cared for by two parents.
All animals somehow balance between these strategies. The most convenient object for finding molecular mechanisms that increase or decrease the tendency of males to monogamy is again vole. I have already mentioned that females of steppe voles tend to become attached to a partner, although sometimes they change it to him. So, this species has full equality: males also spend a lot of time with their wives and children and take care of them. But in most genetically related species, for example, in meadow or mountain voles, nothing of the kind happens: males and females are found only for sex. To the offspring the male does not show any interest, and the females generally pay less attention to their children than in the well-off complete families of steppe voles.
In the laboratory, love is learned in voles as follows: a young virgin male is placed in a cage together with the same young and inexperienced female for 24 hours. As a rule, six hours after dating enough to make rodents like each other, and spend the rest of the day, having sex (not continuously, but often). To then check whether the male is attached to the partner, he is placed in a cage, connected with two others: one lives his first lover, in the other - an unfamiliar female. The movements of the male are taken on a video camera and the time spent in each room is calculated. It turns out that experimenters have many ways to influence the emotional preferences of the male.
The most important role in the formation of attachment in males of steppe voles is played by the release of dopamine in the adjacent nucleus. There are drugs that block receptors for dopamine, for example the famous haloperidol, which has been used for many years in psychiatric clinics to soothe violent patients. So, if you make a male steppe voles injection of haloperidol before the meeting, then it will mate with the female, but there will be no attachment to it11. No dopamine - no love, sorry. But if, on the contrary, before acquaintance with the female, introduce apomorphine to the animal, which increases the activity of dopamine receptors, then attachment will arise even if there were no sex during six hours of contact.
Such experiments Brandon Aragon and Thomas Curtis, employees of the University of Florida, conducted in 2003. In their later works, it turned out that in reality the picture is even more complicated. In the formation of attachment, at least two types of dopamine receptors, D1 and D2, are involved, and D2 stimulation causes affection for the partner, and D1 is responsible for the reverse side of the medal - lack of interest (or even aggression) to extraneous females. After the first meeting of a male monogamous voles with his future wife, he develops sympathy for her (that is activation of D2 receptors), and during the first weeks of life in the male brain, the activity of D1 receptors gradually increases, and he loses all interest in other potential partners . Polygamous voles to such subtle senses are not capable, because they initially differently distributed receptors to dopamine in the brain.
While researchers from Florida continue to tinker with dopamine - making brain sections, picking up pharmacological preparations and introducing monogamous and polygamous males to new females, - Larry Yang from Emory University went on the other side and has already learned how to convert polygamous meadow voles into dedicated husbands using gene therapy .
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The DNA of the bad guy
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