Evolutionary theorists try to understand the evolutionary advantages of human behaviors. Love, they believe, developed as the human form of three basic instincts: the need to be protected from outside threats, the instinct of the parent to protect the child, and the sexual drive. Love is an evolutionary strategy that helps us form the bonds we need to reproduce and pass our genes on to the next generation. We love in order to propagate the species.
To evolutionary theorists, that would explain why we tend to fall in love with people whom we think have positive traits; we want to pass those traits along to our children. In fact, evolutionary theorists argue that their perspective can explain why heterosexual men look for attractive women, and heterosexual women look for successful men, the world over (see the section on cultural influences on attraction on page 194). Heterosexual men want a fit, healthy woman to carry their offspring, and heterosexual women want a man with the resources to protect them and help care for the infant in the long period they devote to reproduction. For most of history, that included 9 months of pregnancy and over a year of breast-feeding. Love creates the union that maximizes each partner’s chance of passing on their genes to the next generation.