As already pointed out, there are large communities of Garos living outside the Garo Hills in the plains of Assam and East Pakistan. The Garos are divided into various sub-tribes with varying customs and manners. But the main septs or clans into which the race is divided are three, the Maraks, the Momins and the Sangmas. Each sept is exogamous, marriage within the clan being strictly taboo. Some sub-clans like the Abengs, Arengs, and Siras are beginning to branch away from the original clans and are developing into independent exogamous clans.