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 Redstone to evaluate individual belief in respect to blood among Jehovah's Witnesses. The study showed that 12% were willing to accept transfusion therapy forbidden by Jehovah's Witness doctrine. One peer-reviewed study examining medical records indicated a similar percentage of Jehovah's Witnesses willing to accept blood transfusions for their children. Young adults also showed a willingness to accept blood transfusions. In another study, Jehovah's Witness patients presented for labor and delivery showed a willingness to accept some form of blood or blood products. Of these patients, 10 percent accepted whole blood transfusion. Watch Tower publications have noted that within religions, the