In most societies adolescence in marked by social as well as biologic changes. Such social changes often include a new, more formal attitude toward parents and, more particularly, toward members of the opposite sex. In many societies the custom is for young people in the early stages of adolescence to spend time in same-sex groups. Boys may attend sporting events, and girls, overnight parties. Eventually the same-sex groups come into contact with similar groups of the opposite sex at social occasions. In some societies young people go out with mixed-sex groups before they begin dating, but in other countries the practice of dating emerges from the same-sex group phase, as individual young people meet and pair off. Often dating is followed by a stage of 'steady dating' in which a couple agree to date only each other, and their exclusive dating relationship may become recognized by their peer group and others, including their respective parents. If the couple gets along well together, the phase sometimes defined as courtship may begin. In its strictest sense courtship usually refers to art activity, such ms dating, with intent to marry. Prior to the 20th century, and still today in some societies, courtship was practiced without dating in the modern sense. A young man might visit his intended bride in her parental home and bring gifts, discuss common interests, and perhaps go for walks. To nontraditional people these customs, if continued to courtship, may seem ridiculously old-fashioned, and it is frequently difficult in the modern era to make meaningful distinctions between 'going out' dating, and courting. The distinctions are further blurred by modern couples' living together, either before marriage or with no intention of ever marrying. More typically, though, the family begins with marriage, which grows out of courtship and is preceded by what sociologists call mate selection. Mate selection may be defined simply as the process, often unconscious, of choosing a mate. Usually the mate is the person’s intended spouse, and the traditional definition of the term has this implication. Individuals often claim that their match is made on the basis of love, but statistical studies show that other factors are involved. For ex ample, people usually marry within their social class and often to those of the same ethnic group or religion. This practice of like marrying like is known as homogamy. Mate selection is also frequently related to economic factors. For instance, be fore she will consent to marry him, a woman may want her intended husband to show that he is capable of supporting her. According to this passage, ______.