ABO blood group system each parent; each has a 25% chance, but some occur more than once. Historically, ABO blood tests were used in paternity testing, but in 1957 only 50% of American men falsely accused were able to use them as evidence against paternity. Occasionally, the blood types of children are not consistent with expectations—for example, a type O child can be born to an AB parent—due to rare situations, such as Bombay phenotype and cis AB. The A blood type contains about 20 subgroups, of which A1 and A2 are the most common (over 99%). A1 makes up about 80% of all
Blood type diet type diet hypothesis and no clinical evidence that it improves health. Peter J. D'Adamo, a naturopath, is the most prominent proponent of blood type diets. Luiz C. de Mattos and Haroldo W. Moreira point out that assertions made by proponents of blood type diets that the O blood type was the first human blood type requires that the O gene have evolved before the A and B genes in the ABO locus; phylogenetic networks of human and non-human ABO alleles show that the A gene was the first to evolve. They argue that it would be extraordinary, from the perspective