Blood group B has its highest frequency in the
Middle East, where it ranks as the largest share of the population. In
Southeast Asia its share of the population is lowest, especially in Indonesia, secondarily in
East Asia,
Northern Asia and neighboring
Central Asia, and its incidence diminishes both towards the
east and the
west, falling to single-digit percentages in
Netherlands,
Norway,
Portugal and
Switzerland. It is believed to have been entirely absent from Native American and Australian Aboriginal populations prior to the arrival of
Europeans in those areas. Blood group A is associated with high frequencies in
Europe, especially in
Scandinavia and
Central Europe, although its highest frequencies occur in some Australian Aboriginal populations and the
Blackfoot Indians of
Montana, US. == Maps of ABO alleles among native populations ==