However, as society developed, human reproductive behavior became more complicated and aggravated by morality and social norms. The institution of marriage appeared, which fixed monogamous couples. Relationships held together by such bonds were supposed to be something eternal, to the grave and beyond. True, love in such marriages was rare, and choosing another partner was considered treason and severely punished in many cultures.
In parallel with the complication of culture, medicine developed, contraceptives appeared, and soon the love that was necessary for the survival of the species was left in isolation from the function of reproduction.


“Ordinary falling in love, a certain sexual impulse lives no more than two months. During this period, both partners demonstrate to each other a kind of demo version of themselves. And rare people try to be sincere with themselves. The motives for such behavior are overcoming two main fears: the male basic fear “I can’t” and the female one — “they don’t want me, they don’t love me.”That is, from the state of these fears, partners try to seem like someone, proving to themselves that after all “they can” and still “they want and love them”, only haste and unwillingness to understand the choice, in the diagnosis of a partner, create a lot of disappointment and problems that are just clarified after about two months. Pretending is already difficult and irritation from insincerity is accumulating, ”comments psychologist and psychodiagnostic Anna Sukhova.