Experiments helped to understand the genetic nature of aggression
«Guys, let's live together!» — said the pathologically kind cat Leopold from the famous cartoon, and when beliefs did not help, he drank Ozverin. It turns out that in order to get really angry at the mice that annoyed him, Leopold had to resort to a completely different means. Why, we were told at the Institute of Cytology and Genetics of the Siberian Branch of the Russian Academy of Sciences, where for 50 years they have been conducting the only experiment in the world — they bring out two opposite «civilizations» of animals — aggressors and good-natured people, and sometimes, for the sake of experiment… they change their characters!
Rimma Kozhemyakina with a pet rat. Photo: Fedoseeva A.V.
As subjects — the descendants of gray street rats, which were once caught on farms. Evil people were put in one cage, sympathetic people — in another. And so they did with their children, grandchildren, great-grandchildren, etc. — for several decades. The metamorphoses that occurred with the “mongrels” rats are amazing: the kind ones squeal with joy when their favorite laboratory assistants approach the cage, they immediately ask to be “handled”, and perched higher, they immediately climb to kiss.
Their antipodes, from which real beasts have been raised for a hundred generations, also fly out to meet the laboratory assistant, but with a different goal: to bite through his hand as painfully as possible. It's good that special, reinforced gloves always save.
People who are far from science will say: “Well, why is all this necessary ?! Wouldn't it be better to leave the animals alone?» But scientists have their own reason. They set a goal — to see how evolutionary habituation of a wild animal to a person took place, to breed the most benevolent rat, and it seems that they succeeded. The rat is one of the most easily trained animals and can serve us well as a laboratory species, and just as a pet.
The aggressive line was a kind of «by-product» in the selective selection of good rodents. But it also came in handy: scientists want to understand the genetic nature of rat aggression. Perhaps in the future this will help some people get rid of bad character traits.
In February, the appearance of the 100th generation of benevolent rats was reported in the vivarium of the Institute of Cytology and Genetics of the Siberian Branch of the Russian Academy of Sciences. All 200 pets — «diagnosis» — the maximum friendliness with estimates from +3.5 to +4 points, although their great-great-grandmothers, out of the kindness of their souls, did not even reach 0 points — their degree of «philanthropy» was estimated on average from up to -2.5 to -1.5 points. But as time went on, selective methods did their job. The 100th generation of benevolent rats is already strikingly different from their ancestors. But those in whom evil outweighed, dropped from the average to the extreme degree of aggression — up to -4 points. There are now 150 such individuals in the vivarium.
An employee of the laboratory of evolutionary genetics, junior researcher Rimma Kozhemyakina explains how the so-called “glove test” is carried out for each generation:
Usually, the rat's propensity for one or another type of character is determined by its reaction to the employee's hand stuck into the cage. If the animal approaches her, takes an interest, sniffs, — it is determined in one direction, if it immediately pounces and bites, — in the opposite direction. Further, an additional test is applied for benevolent ones: if the rat, which was picked up, twists and tries to run away, they give it +3 points on our scale, if it sits calmly and its body is relaxed, then they give it almost maximum +3.5 points. Aggressive rats also have a gradation in assessing behavior: if you approach the cage, open the door, put your hand in, and at that moment it throws itself at it from the back wall, we set -3.5 points, and if it does not even allow you to place your hand, — sits at the near wall in advance and is ready to pounce on the glove, then this is -4 points — the maximum degree of aggression.
Scientists do not only selection of rats, but also study the features of their behavior, physiology and genetics.
“The psychological characteristics of kind and aggressive animals are best manifested in the upbringing of cubs and “interpersonal” relationships when living in a group,” explains Kozhemyakina. “For example, when feeding, aggressive mothers feed their cubs from a standing position (the so-called arched type of feeding). This is the most labor-intensive a pose for the female, but with the maximum return for the cubs. Benevolent ones are more likely to feed from a relaxed position lying on their side or simply lie on their stomach on their offspring. «
According to the laboratory employee, this type of behavior of kind females, which borders on less motivation to raise strong offspring, indicates their low level of anxiety for their offspring, they are more busy with themselves, studying the outside world, more often they leave the nest, communicating with a person.
When the pups reach 45 days of age, they conduct a “glove test” with each, determining the kindest and most evil, and then send a certain number of them to the breeding “core”. The rest, the middle peasants, are simply culled.
At the first meeting, an aggressive rat grabbed an institute employee's hand. Photo: Fedoseeva A.V.
It is interesting how selected individuals behave in a flock of their own kind. According to Rimma Kozhemyakina, the males of both «civilizations», of course, immediately build a hierarchy in the cage: everyone obeys the largest, dominant «guy». Attempts to approach the feeder ahead of him end sadly for the daredevils: there have even been deaths among aggressive rats.
— Kind rats fight more interesting, — the employee says, — they stand opposite each other in the pose of boxers and «waltz» in anticipation of the one who first hits with his paw.
All staged behavioral experiments, especially with the use of pharmaceuticals, are carried out in the laboratory only on males — they do not have hormonal changes, like in females, which greatly simplifies the matter.
In particular, research on the effects of oxytocin (a hormone that affects levels of anxiety) began in the 2000s. It was important for scientists to unravel the mechanism of its effect on the brain, because people cannot dig into it.
The nasal agent was dripped into the nose of the rats once for five days and unexpectedly produced a surprising, partly unpredictable result. Aggressive males have become kind, and kind males have become aggressive from the same doses of oxytocin! We checked this under equal conditions for both: neutral, laboratory white relatives were put into a cage in which one owner was sitting — a male rat receiving oxytocin. If in a normal situation the aggressor immediately pounced on them and, relatively speaking, tore them to pieces, then after oxytocin his anger was not direct, more demonstrative than effective: the male simply let out the undercoat, becoming larger in the eyes of strangers, pushing them into a corner. Kind males, after the same doses of the drug, became their antipodes and resembled the kind cat Leopold after a horse dose of Ozverin: they immediately dug into the neck of the guests.
Interestingly, this effect of oxytocin was manifested only in adults — it had no effect on «teenagers» from both groups.
Scientists checked the aggressors and good-natured people and for addiction to alcohol. Of course, they didn’t pour cognac for them — only medical alcohol, and even then, diluted to a 7-degree fortress. So, oddly enough, benevolent rats leaned on him more, and the aggressors preferred pure water to alcohol. Scientists wanted to investigate this incident, but, alas, without receiving funding, they were forced to focus on other aspects of good and evil.
Here, who, for example, will be an excellent student in school — an aggressive person or a kind one? Since you can’t put a rat at a school desk, they came up with a task for it in the pool.
“This is the so-called Morris water test,” Rimma Kozhemyakina clarifies. — A rat is launched into a pool with a diameter of a meter and it swims in it. Our wards swim very well, but, anyway, they are uncomfortable in the water. And in the pool there is a place where you can stop, feeling a special stand under your paws, and relax. Only now this stand is hidden under water, and so that the rat does not immediately notice it, the water is whitened with milk … After a few minutes of swimming, the animal still finds a saving «reef» and rests. In order for it to remember this place, large black figures are specially drawn on the walls of the mini-pool for orientation: circles, triangles, squares. Result: tame rats found a safe place by reference points already on the second day of training, but aggressive rats needed all four days to learn the lesson. Their high level of anxiety contributed to poor learning.
But could a friendly environment influence the children of aggressive parents? Biologists somehow thought about this and planted rat pups from aggressive parents to benevolent mothers, and tame ones to aggressive ones.
— This is the so-called cross-fostering test (Cross-fostering — cross-education — Auth.), — explains Kozhemyakina. — But it did not lead to any changes in the behavior of grown rats towards humans. Both sympathy and aggression turned out to be qualities strongly fixed at the genetic level.
– It turned out that there is. We see that if in the 40th or 50th generation of rats individuals were born that did not reach the “evil” or “good” maximum of 3 points, now this is not the case. All on average reach values: either -3.5 or +3.7 points.
We have not yet observed this in the rat population, with the exception of isolated cases when aggressive couples, a baby rat is born, in which the score is reduced by one compared to relatives.
— You can be one hundred percent sure that a bred tame rat will never bite a person, no matter if it is the owner or a stranger. Often we distribute rats that are no longer participating in experiments to friends. And this is what the episode was associated with such a rodent, which the new owners named Ronnie. He freely walked around my girlfriend’s apartment, and when I came to visit her, Ronnie climbed onto the sofa, lay down next to me on his back and began to ask, demonstrating how to do it, with a paw, so that I would scratch his belly. I obediently stroked, and he fell asleep (Smiles).
I won’t be surprised that under such conditions, a rat with a good pedigree and education based on black squares and a bath of milk will soon not only make the belly scratch, but also sing like a nightingale. By the way, ICG staff have already figured out how to further enrich its habitat — for the future 101st generation, they want to build more spacious cages (four times more spacious than the previous ones) with shelves to overcome obstacles, with a wheel and a hammock.