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 by failing to report any benefits of blood-based treatment. Nor do its publications acknowledge that in some situations, including rapid and massive haemorrhage, there are no alternatives to blood transfusions. He claims Watch Tower Society publications often discuss the risk of death as a result of refusing blood transfusions, but give little consideration to the prolonged suffering and disability, producing an added burden on family and society, that can result from refusal. Attorney and former Witness Kerry Louderback-Wood also claims that Witness publications exaggerate the medical risks of taking blood and the efficiency of non-blood medical therapies in critical situations.