Some groups adapted to the environment in new ways while others remained hunter/foragers. Settled agriculture appeared in several different parts of the world. The switch to agriculture created a more reliable, but not necessarily more diversified, food supply. Agriculturalists also had a massive impact on the environment, through intensive cultivation of selected plants to the exclusion of others, through the construction of irrigation systems and through the use of domesticated animals for food and for labor. Populations increased; family groups gave way to village and later urban life with all its complexity. Patriarchy and forced labor systems developed giving elite men concentrated power over most of the other people in their societies.