There are numerous historical instances of a single individual becoming the forefather of a tribe or a collection of tribes which under favourable conditions may develop into a nation.

The tribe or people is known as the "sons" of their ancestor; his name is handed down from generation to generation, and the names of his leading descendants, the representatives of the tribe, are handed down at the same time.

Where we speak of the population of a country, the Arab speaks of the "children" of a certain man.

Such a mode of expression is in harmony with Semitic habits of thought.

The genealogical method prevails alike in history and geography; a colony is the "daughter" or "son" of its mother-city, and the town of Sidon is the "first-born" of Canaan.
Jacob had twelve sons, and his descendants were accordingly divided into twelve tribes.