A man can become a biological father in a matter of minutes. A woman spends enormous resources on a child: nine months of pregnancy, risks during birth and years of feeding. That's why evolution implanted in us a secret algorithm of love. Men unconsciously look for women with high fertility, and women - those who have the resources to protect their offspring. Our explanation# deals with the illusion of choice and that behind love at first sight there are millions of years of natural selection.