Unlike marriage, sex, and procreation, romantic love has not always been a part of life; even today, the concept is virtually unknown in traditional societies. In order for romantic love to take root in a society, there has to be a certain amount of wealth and leisure. There also has to be a period between the first manifestations of sexual desire, which typically happen in puberty, and their fulfillment. In societies where most people are poor and live off the land, there is a great incentive to marry at puberty and start having offspring so that children can help on the farm. There is simply no time to fall in love.
The idea of romantic love had existed in ancient Greece and Rome and parts of the Middle East—the Bible's Song of Solomon is clear evidence of this—but had largely faded from Western Europe with the fall of the Western Roman Empire. Then, in the High Middle Ages (1100-1300), it took hold among the upper classes, as the popularity of courtly love illustrates. During the thirteenth century and later, the concept spread to the middle class. Marriage prior to that time had been chiefly a business arrangement, with the young man's family offering some advantage to the young woman's family, and the latter providing a dowry (the wealth that a bride brings to a marriage) in exchange. Perhaps the couple might grow to love one another, but this was only a happy accident, and not considered a vital part of marriage.
With the emergence of the middle class, however, it became possible for a young man and woman to marry for love, and not primarily for money. Ironically, the people who were least free to marry for love were the most wealthy and powerful: the motivation behind the vast majority of royal or noble marriages remained political or economic, not romantic.
The other hand, considered science a threat to its dominant position in European intellectual life.