Why do animals and people sacrifice themselves?

Biologists call selfless behavioranimal altruism. In nature, altruism is quite common. Scientists cite meerkats as an example. When a group of meerkats is in search of food, one selfless animal takes an observant position to warn relatives about the danger in case of approaching predators. At the same time, the meerkat itself remains without food. But why do animals do this? In the end, Charles Darwin's theory of evolution tells of natural selection, which is based on the "survival of the fittest." So why in nature does self-sacrifice exist?

Altruistic behavior is common among meerkats

Gene Survival Machines

For many years, scientists could not find an explanationaltruism. Charles Darwin did not hide the fact that he was concerned about the behavior of ants and bees. The fact is that among these insects there are working individuals that do not breed, and instead help to raise the offspring of the queen. This problem remained unresolved for many years after the death of Darwin. The first to explain selfless behavior in 1976 was Richard Dawkins, a biologist and popularizer of science, in his book The Selfish Gene.

In the photo, the author of the book “The Selfish Gene,” British evolutionary biologist Richard Dawkins

The scientist conducted a thought experiment, suggestingthat altruistic behavior can be explained by a special type of gene. More specifically, Dawkins book is devoted to a special view of evolution - from the point of view of a biologist, all living things on the planet are “machines” necessary for the survival of genes. In other words, evolution is not only about the survival of the fittest organisms. Dawkins evolution is the survival of the fittest gene through natural selection, which favors genes that can best replicate themselves in the next generation.

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Altruistic behavior in ants and bees candevelop if the altruism gene of the working individual helps another copy of this gene in another organism, for example, in the body of the queen and her offspring. Thus, the altruism gene provides its representation in the next generation, even if the organism in which it is located does not produce its own offspring.

Dawkins's selfish gene theory solved the issuethe behavior of ants and bees, which Darwin reflected on, but raised another. How can one gene recognize the presence of the same gene in the body of another? The genome of brothers and sisters consists of 50% of its own genes and 25% of the genes from the father and 25% from the mother. Therefore, if the altruism gene “forces” a person to help his relative, he “knows” that there is a 50% chance that he helps to copy himself. This is how altruism developed in many species. However, there is another way.

Green Beard Experiment

To emphasize how the altruism gene canto develop in the body without helping relatives, Dawkins proposed a thought experiment called "green beard." Let's introduce a gene with three important characteristics. Firstly, a certain signal should indicate the presence of this gene in the body. For example, a green beard. Secondly, the gene must be allowed to recognize a similar signal from others. Finally, the gene should be able to “direct” the altruistic behavior of one individual to one that has a green beard.

In the photo, the working ant-altruist

Most people, including Dawkins, consideredthe idea of ​​a green beard as a fantasy, and not as a description of any real genes found in nature. The main reasons for this are the low probability that one gene may possess all three properties.

Despite the apparent fantastic, in recentyears in biology there was a real breakthrough in the study of green beard. In mammals like us, the behavior is mainly controlled by the brain, so it’s hard to imagine a gene that makes us altruists, who also control the perceived signal, such as the presence of a green beard. But in microbes and unicellular organisms, everything is different.

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In particular, in the last decade to studysocial evolution began under a microscope to shed light on the amazing social behavior of bacteria, fungi, algae and other unicellular organisms. One striking example is the amoeba Dictyostelium discoideum, a unicellular organism that responds to a lack of food by forming a group of thousands of other amoeba. At this point, some organisms altruistically sacrifice themselves, forming a sturdy stalk that helps other amoebas to disperse and find a new source of food.

This is what the amoeba Dictyostelium discoideum looks like

In a similar situation, the unicellular genereally can behave like a green beard in an experiment. A gene located on the surface of cells is able to attach to its copies on other cells and exclude cells that do not match the group. This allows the gene to guarantee that the amoeba that formed the wall will not die in vain, since all the cells it helps will have copies of the altruism gene.

How common is the altruism gene in nature?

Studying altruism or green beard genesstill in its infancy. Today, scientists cannot say exactly how common and important they are in nature. The fact that the kinship of organisms occupies a special place at the basis of the evolution of altruism is obvious. By helping close relatives to multiply or raise their offspring, you thereby ensure the survival of your own genes. So a gene can guarantee that it helps replicate itself.

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The behavior of birds and mammals also suggests that their social life is centered around relatives. However, marine invertebrates and unicellular organisms are a little different.