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
World Blood Donor Day 1868. World Blood Donor Day celebration brings a precious opportunity to all donors for celebrating it on national and global level as well as to commemorate the birthday anniversary of the Karl Landsteiner (a great scientist who won the Nobel Prize for his great discovery of the ABO blood group system). The theme for Blood Donation Day in 2018 is 'Be there for someone else. Give blood. Share life' The theme for Blood Donation Day in 2017 focus on blood donation in emergency situations. The first response when an emergency happens is "What Can You Do?" and the answer is