The ancient Greek city state of Sparta was ruled by a Gerousia. A Gerousia was a council made up of members who were at least 60 years old and served for life. The political power within the ruling class accumulates with age, making the oldest the holders of the most power. In many preindustrial societies, the elderly still have influence and power and their vast knowledge is respected. This type of political and social structure is known as a .