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
Jehovah's Witnesses and blood transfusions contain a small amount of blood. Jehovah's Witnesses' view of meat and blood is different from that of kosher Jewish adherents, who go to great lengths to remove minor traces of blood. Jehovah's Witnesses and blood transfusions Jehovah's Witnesses believe that the Bible prohibits ingesting blood and that Christians should not accept blood transfusions or donate or store their own blood for transfusion. The belief is based on an interpretation of scripture that differs from that of other Christian denominations. It is one of the doctrines for which Jehovah's Witnesses are best known. Jehovah's Witnesses' literature teaches that their refusal