HLA DR3-DQ2 is not spread evenly in the among humans. It is has a substantially higher frequency in the western world, except indigenous Native American. It is virtually absent in some Asian populations. It current world distribution suggest that it spread from Africa with a wave that spread late in human evolution which reached central Asia more recently, a possibility is that it spread with agrarian cultures that migrated from Africa. Percentage is 6.5% to 27.4%