Maternal and Paternal Instincts: Biochemical and Physiological Mechanisms / Материнский и отцовский инстинкт: биохимические и физиологические механизмы.

Maternal instinct is not merely an emotional phenomenon but a result of complex genetic, biochemical, and neurophysiological mechanisms. During pregnancy, the mother and fetus form a unified biological system. The mother transmits not only half of the nuclear genome but also mitochondrial DNA, inherited exclusively through the maternal line. Fetomaternal microchimerism, in which fetal cells persist in the maternal body for decades, creates a long-term physical connection beyond childbirth. Hormonal shifts involving oxytocin, prolactin, estrogens, and dopamine restructure the maternal brain, enhancing attachment and transforming childcare into a source of reward. In men, there is no automatic biochemical trigger due to the absence of gestation, but active caregiving can also elevate oxytocin and prolactin levels, leading to neurobiological adaptation. Thus, maternal instinct is biologically determined, while paternal instinct develops primarily through social interaction and experience.