ABO blood group system and likely predates human migration from Africa. The O01 allele is considered to predate the O02 allele. Some evolutionary biologists theorize that there are four main lineages of the ABO gene and that mutations creating type O have occurred at least three times in humans. From oldest to youngest, these lineages comprise the following alleles: "A101/A201/O09", "B101", "O02" and "O01". The continued presence of the O alleles is hypothesized to be the result of balancing selection. Both theories contradict the previously held theory that type O blood evolved first. It is possible that food and environmental antigens (bacterial, viral, or
Blood type (non-human) blood. Two categories of blood groups, human-type and simian-type, have been found in apes and monkeys, and can be tested by methods established for grouping human blood. The rhesus system is named after the rhesus monkey, following experiments by Karl Landsteiner and Alexander S. Wiener, which showed that rabbits, when immunised with rhesus monkey red cells, produce an antibody that also agglutinates the red blood cells of many humans. Data on blood groups of chimpanzees, baboons, and macaques. Two complex chimpanzee blood group systems, V-A-B-D and R-C-E-F systems, proved to be counterparts of the human MNS and Rh-Hr blood group