Agrarian societies use agricultural technological advances to cultivate crops over a large area. Sociologists use the phrase agricultural revolution to refer to the technological changes that occurred as long as 8,500 years ago that led to cultivating crops and raising farm animals. Increases in food supplies then led to larger populations than in earlier communities. This meant a greater surplus, which resulted in towns that became centers of trade supporting various rulers, educators, craftspeople, merchants, and religious leaders who did not have to worry about locating nourishment.