A tribe was a type of social group, usually smaller than a nation. They were common in civilisations that were not technologically advanced.
The Doctor encountered many human tribes throughout time and space, from the Tribe of Gum on prehistoric Earth (TV: An Unearthly Child) to the Sevateem and the Tesh in the far future. (TV: The Face of Evil) The Tribe of the Free lived on Ravolox in 2000000. (TV: The Mysterious Planet)
In Africa, the Fourth Doctor, Sarah Jane Smith and Harry Sullivan encountered a tribe in Nyasaland. (PROSE: To Kill a Nandi Bear)
In South America in 1924, George Cranleigh encountered the Kojabe tribe and an unnamed tribe led by Latoni. (TV: Black Orchid) The Second Doctor, John and Gillian encountered a South American tribe and helped them fight off an enemy tribe. (COMIC: The TARDIS Worshippers)
Other species which formed tribes included Neanderthals (TV: Ghost Light), Silurians (TV: The Hungry Earth/Cold Blood), Swampies (TV: The Power of Kroll), and the Sycorax (TV: The Christmas Invasion). The First Doctor, John and Gillian encountered a hostile tribe on an unnamed planet. (COMIC: The Didus Expedition)
