Charles Darwin's theory of sexual selection as the basis of modern evolutionary psychiatry and psychology: from invertebrates to birds

The article analyzes the theory of sexual selection (in the evolutionary series from invertebrates to birds) by Charles Darwin, presented by him in the monograph “The Origin of Species and Sexual Selection.” According to Darwin's theory, in the lowest parts of the animal kingdom, sexual selection has no significance; its effect is observed only starting with arthropods (crustaceans, arachnids, insects) and vertebrates (and already among some representatives of the class of insects and reptiles, according to Darwin, a feeling of "attachment" is observed) Darwin identified three types of sexual selection: 1) with choice on the part of the female (the most common in the animal world); 2) with choice on the part of the male; 3) with mutual choice. All three types of choice provide one advantage: raising more offspring. In constant living conditions, there is a limit to the action of natural selection; sexual selection does not have such restrictions; it is limited due to the action of natural selection, for example, the coloring of male birds that is too attractive for females can make the males more vulnerable to predators. According to Darwin's analysis of the sexual behavior of animals, in birds, reptiles, fish, crustaceans (and mammals), differences between the sexes follow almost exactly the same rules. Males court females and have weapons to fight rivals; they are larger and more pugnacious. In almost every class there are several anomalous cases in which there is an almost complete perversion of the characteristics of both sexes, with females acquiring typically male characteristics (pugnacity, bright coloring, large size). Systematized by Darwin, the differences in the lifestyle of males and females, which, according to his theory, determine structural signs of sexual dimorphism, postulation of the appearance of anomalies and an increase in the risk of mortality depending on sex, established connections between bright colours and increased pugnacity in birds, evaluation of various patterns of animal behaviour as methods of attracting a female, and the formulation of the position according to which the instinctive behaviour of animals can be carried out simply “for pleasure”, as if separated from its original purpose, served as a “matrix” for the interpretation in modern evolutionary psychiatry and psychology of the meaning of sex differences by mental disorders.