This document summarizes the earliest forms of human social organization: families, clans, and tribes. It describes families as nuclear (parents and children) or expanded (including other relatives). Clans are descent groups that share a common ancestor but may not know exact genealogy. Clans typically own land and have their own territory. Tribes are larger groups united by a shared language and customs that sometimes call themselves nations. Within tribes, social organization occurred through families, clans, bands, and villages.