I found this interesting tidbit in Wikipedia's entry on the Blood Type Diet:
Yamamoto et al. further note:
Although the O blood type is common in all populations around the world, there is no evidence that the O gene represents the ancestral gene at the ABO locus. Nor is it reasonable to suppose that a defective gene would arise spontaneously and then evolve into normal genes.
What does this mean? That normal genes suddenly arise spontaneously and then defective genes follow as a result of mutation? Wouldn't it be logical for an evolutionist to believe that all normal genes be the results of mutations from previously less functional [defective] genes? Without realizing it, Yamamoto made a statement that supports intelligent design and I agree with it 100 percent.
 Mourant AE, Kopec AC, Domaniewska-Sobczak K. The distribution of the human blood groups and others polymorphisms. London: Oxford University Press, 1976. 140p.
 Saitou N, Yamamoto F. Evolution of primate ABO blood group genes and their homologous genes. Mol Biol Evol 1997; 4(4):399-411.