Abstract To identify the similarities and differences among a series of human populations based on variations in genetic frequencies. DATA The frequencies of genetic variants within three major red blood cell systems (ABO-system, Rh-system, and MN-system) for 26 race/ethnicity groups were collected from a variety of sources. The presence of genetic variation in human blood was first established by Lansteiner in 1901 with the identification of different blood group types, now called the ABO-system. The Rh­ and MN-systems also contain well-known and reliably identified genetic variants. Using these three red blood cell systems (a total of 13 variants), the genetic distances between the members of the 26 populations can be estimated (325 distances). Data consisting of summary values (such as genetic frequencies) rather than individual measurements are commonly referred to as aggregate or ecologic data.