In theory, the different blood groups evolved in different parts of the world depending upon the type of environment, society and availability of food sources. For example:

Blood type O is the generally considered the oldest blood type showing a prevalence for hunter-gatherer cultures. Because of the high protein content of their diet, group O individuals tend to secrete higher amounts of stomach acid in order to digest the protein. Therefore, it is not surprising that group O individuals have a greater incidence of gastric ulcer disease than the other blood groups. Blood group O is about 46% of the American population.

Blood group A was the next to evolve and emerged with the development of agricultural practices. Blood group A can be broken down into A2 and A1, with A2 having evolved sooner than A1. Blood group A is primarily associated with vegetarian food sources and individuals in that group secrete smaller amounts of stomach acid. Protein requirements are not any less than a group O person but the source is different. Group A2 persons can handle higher amounts of animal protein than A1 persons who look for their protein from vegetable and legume sources. Group A comprises 42% of the American population and group A1 comprises 80% of the group A individuals.

Blood group B was the next to evolve and is associated with cultures which use higher amounts of fermented dairy products. Persons who are blood type B tend to do better on diets which are high in dairy products and fish. Group B persons tend to have higher incidences of urinary tract diseases, such as kidney and bladder infections. This is due to an absence of the alloantibody B which conveys a greater protection against bacterial infections. Group B persons make up about 7% of the American population.

Blood group AB was the last to evolve and has been dubbed the "modern diet" blood type by D'Adamo & Powers. This is because an AB person combines the characteristics of groups A & B and therefore can tolerate a wider range of foods. Blood group AB persons can tolerate small amounts of many different foods where as the other blood groups will show a dietary or systemic reaction. Group AB persons tend to tolerate diets high in seafood, some dairy, nuts and grains. Blood group AB comprises 4% of the American population.

Importance of Serotyping
The reason blood grouping is important in determining a persons diet is because of dietary lectins which are found in foods. If dietary lectins pass undigested into the intestinal tract, they are either recognized as self or non-self by the body's immune system. Cooking eliminates a large percentage of dietary lectins but not all. Therefore, if digestion is compromised, a small percentage will make it through into the intestinal tract. It stands to reason that if raw foods are eaten, a greater percentage of lectins will pass into the intestinal lumen. However, if the proper amount of food enzymes are present, this does not occur as the enzymes will complete the digestion.

Not all dietary lectins are incompatible. Depending upon the blood grouping, the body's immune system will register the lectin as compatible and will not react to remove them. When the body perceives the lectins as non-self, they are removed from the intestinal tract by a nonspecific immune reaction which results in the release of histamines, activation of complement and IgA, resulting in inflammation. This nonspecific reaction is thought to be the basis of the food sensitivity testing done by the Voll or Vega methods. Prolonged gastrointestinal inflammation results in increased permeability of the gastrointestinal tract. Eventually the intestinal brush border breaks down resulting in unrestricted macromolecule permeability and eventual antibody formation. If it is the first exposure, IgM levels begin to rise, or if it a subsequent exposure, serum IgG levels will begin to rise or circulating immune complexes will be detectable. Either way it means that the person is now at high risk for the development of other diseases. This is thought to be one of the mechanisms of the development of chronic degenerative diseases such as arthritis, lupus, nephritis and cancer.