When elderly people are considered elders and leaders of a group of people, they are functioning under a (n)

When elderly people are considered elders and leaders of a group of people, they are functioning under a gerontocracy, it's a form of rule in which the leaders are significantly older than most of the population. An example of gerontocracy would be the Gerousia, in ancient Greece, which was made of members with more than 60 years that had served for their whole lives.