Living organisms can act for the benefit of related individuals, since such actions contribute to the transfer of common genes to the next generation.
The problem of altruism has traditionally raised many questions in the theory of evolution. For example, a monkey that detects an approaching leopard can raise a cry to warn relatives, although this increases the risk to itself. The most unsophisticated view of natural selection is that the genes that cause the monkey to sound alarm cries should eventually disappear from the population, as they reduce the fitness of the individual. Nevertheless, altruistic behavior is observed in all animal species (including humans). Why is this happening?
Kindred selection theory has attempted to explain this and other mysterious aspects of animal behavior. The basic idea is this: related individuals have a certain set of common genes. So, you (like your brothers and sisters) have half of your genes inherited from one parent, half from the other. For evolutionary theory, it is not the survival of individuals that is important, but the transfer of genes to the next generation. If a monkey that raised a cry at the sight of a leopard has, say, three siblings in the group, then from the point of view of statistics, we can say that in this situation the individual who sacrificed itself can pass on more genes to the next generation than the surviving one. As evolutionary biologist JBS Haldane wittily observed,"I would lay down my life for two siblings or eight cousins."
For example, the peculiarity of bee reproduction is such that each female bee receives all the paternal and half of the maternal genes. This means that worker bees will have 75% of their genes in common (mammals with the same degree of relationship have 50% of genes in common). Therefore, by helping a sister become a queen bee, the worker bee will pass on more genes to the next generation than she could if she had her own daughters.
Kindred selection also explains homosexuality in many animal species, including humans. Since, by definition, homosexual behavior precludes the transmission of genes to future generations, one would expect it to disappear even in time immemorial. One of the proposed explanations for the persistence of homosexuality has been quite aptly called the helper in the nest theory. According to this theory, if an individual does not produce offspring, but her actions contribute to the survival of related individuals, she will be able to transfer more genes to the next generation.
The phenomenon of kin selection to some extent refutes our understanding of evolution. Instead of being guided by the fitness of individuals, as Darwin did, we are being asked to be guided by the fitness of genes. This view leads to the concept of the "selfish gene". The essence of this concept is that the transfer of genes to the next generations is important for evolution and that those whose behavior provides an advantage to the genes survive, although for the individual himself such behavior can be very harmful. Or, as one witcher put it, "a chicken is just a way to get another out of one egg."