It never dawned on me till the other day that tribunes were the leaders of various Roman tribes. In the early days of Rome, there were only three, but over time they expanded out to 35 different tribes, each with different names, and were actually ordered by number. They were even recorded as having official dates of establishment.
Now clearly the term here "tribes" has a different meaning than the modern English term which means "a group of people that includes many families and relatives who have the same language, customs, and beliefs". These tribes appear to be politically created entities.
They were largely the basis for the early government of the Roman Republic as the comitia tributa, or Tribal Assembly. They elected the quaestors, aediles, and tribunes that governed and managed the state, which is something I'm more familiar with.
It's just that these "tribes" threw me for a loop since I never really heard of them, and now I would like to know more about them.
The three tribes are a distinctive feature of a number of Indo-European societies, and it's been suggested that it may have its roots in a much earlier prehistoric system. They appear in Greece--the Athenians and Peloponnesians had different names for their original three tribes, and the subdivision of each of Cleisthenes' ten tribes into trittyes, or thirds, derives from this organization. Originally the three tribes were more or less as you describe the standard English definition of a tribe--while they were not separate nations they appear to have had separate traditions and were something similar to "clans." The ten tribes at Athens and the tribes of the Tribal Assembly at Rome were divided more or less arbitrarily--Livy has a somewhat confused description of the initial processes of organizing the tribes, although he doesn't seem to fully understand what exactly happened. At Rome the city tribes were divided according to area, and what tribe you were in originally depended on where you lived. Of course, since you belonged to the same tribe as your father pretty soon the geographic distinctions were meaningless. The rural tribes were also originally geographical, although the origin of the names of the rural tribes is uncertain. It seems that although the rural tribes were given the feminine forms of distinguished family names they did not descend from these families at all--this seems to be a holdout from the practice of naming the three Indo-European tribes, which were always given influential feminine names in every society in which they appear.
The Tribal Assemblies were a way originally to allow those outside the senatorial class to exercise some political power, by electing quaestors and curule aediles (the Plebeian Assembly, which was just the Tribal Assembly without any non-plebeians, elected the tribunes and plebeian aediles). The Tribal Assemblies were not subdivided into centuries like the comitia centuriata it did not suffer the same problem that the comitia centuriata did, namely that while all centuries voted only the first few centuries (composed almost entirely of patricians or the sentorial class) had their votes actually counted.