were: Northern subgroup (Yerewa): (Aka-)Kari or Cari – N of North Andaman – 2 individuals in 1994 (Aka-)Kora, Khora or Cora – E of North Andaman – extinct by 1994 (Aka-)Bo – W of North Andaman – 15 individuals in 1994 (Aka-)Jeru – S and central North Andaman – 19 individuals in 1994 Southern subgroup (Bojigyab): (Aka-)Kede – N of Middle Andaman – extinct soon after 1931. (Aka-)Kol – SE of Middle Andaman – extinct by 1921. (Oko-)Juwoi – SW of Middle Andaman – extinct by 1931 (A-)Pucikwar – NE of South Andaman and Baratang – extinct soon after 1931. (Akar-)Bale – Ritchie's Archipelago – extinct soon after 1931. (Aka-)Bea – coast of South Andaman and Rutland Island – extinct by 1931. (The prefixed forms of the names actually refer to the respective languages, but they are often used for the tribes themselves.) By 1994 there were also 4 Great Andamanese individuals with no tribal affiliation. The Great Andaman islands run in a north–south line for some 350 km but are only some 50 km wide at its widest extent. This peculiar geography meant that each tribe typically had only two or three neighbours. Indeed, until colonial times, the northern and southern tribes seemed unaware of each other's existence. Except for the Bea and Bale, who had intense and friendly relations and whose languages were mutually intelligible to some extent, there was little interaction between the tribes at the time of first European contacts. The tribes were further split into smaller units—"septs", "local groups", and families—and also between shore-dwellers (aryoto) and forest-dwellers (eremtaga). Population decline Estimates of the Great Andamanese population by the time of the establishment of a British colonial presence (1789–1796) vary between 2000 and 6600 individuals. When the British established a permanent settlement and penal colony on Great Andaman in the 1860s, the population was estimated at 3500. At that time their isolated culture was suddenly confronted with the industrial and colonial culture of 19th century Europe. The colonial administrators proactively tried to pacify and co-opt the tribes, recruiting them to capture escaped convicts. Populations went into sharp decline due to outside diseases. Outside infectious diseases, to which the islanders had no immunity, decimated the tribes at the end of the 19th century; In some cases, people who became sick were killed by other tribe members in an attempt to stop contagion. The migration of Indian settlers