>Not all traditional hunter-gatherer groups were exclusively Type O. For
>example, about three-quarters of the Blackfoot and Blood Indians were Type
>A; ditto for about 30% of the Navajo.
>From an evolutionary perspective, it makes
>little sense that within a population, in which everyone ate the same foods
>for thousands of years, there would be sub-groups with completely different
>dietary needs; hunting tofu was not an option for the Blackfoot.
One of Daniel Quinn's books (either "Ishmael" or "Story of B," I forget
which) mentions that some of the plains Indians were agricultural for a
time, and they became hunter/gatherers again after they learned from the
Spanish how to use horses. Maybe that explains the other blood types?