Looks like type O blood may have been the original blood type. Look at the following which was Excerpted from the Complete Blood Type Encyclopedia by Peter D'Adamo, published by Penguin Putnam Inc, Copyright 2002 and can be found at http://www.dadamo.com/science_anthro.htm along with a lot more information that is fascinating: Ancestral Foundations From a purely scientific point of view, chemical analysis of the group O antigen reveals that from a structural perspective, it is the simplest blood group and it serves as the backbone for the synthesis of increasingly complex A, B and AB. These later blood groups evolved by adding other sugars onto the basic O sugar, much like a modern city might be built upon the foundations of an ancient one. Thus if the mutations that produced the A and B antigens are ancient, the gene for blood group O is infinitely older. Another dimension testifying to the great antiquity of group O comes from the science of physical anthropology and suggests that a greater part of humanity�s existence has been lived exclusively as group O. New studies on mitochondrial DNA (mtDNA) support the theory that Homo sapiens emerged in Africa and only later infiltrated other regions. Unlike DNA, which is inherited from both parents and changes minutely with each generation, mtDNA is passed directly from mother to child. It is contained in eggs but not in sperm. Since only random mutations alter its sequence, it is a more accurate measure of the trajectory of human evolution. Extensive mtDNA studies demonstrate that humans evolved from a common ancestor. These studies also confirm the theory that the blood groups evolved as migratory mutations. The extraordinarily high percentage of blood group O in "ancient" or otherwise isolated populations also testifies to its great age. (6) Even though the early migrations dispersed the gene for group O blood throughout the world, there are some extraordinary examples of "old" populations existing in our world today. Because of their geographic locations, these societies have remained isolated from interaction with other populations. If A, B and O had developed simultaneously, the isolated population groups would have had all of them. But these "old societies" are group O because genes for the later blood groups never had the opportunity to enter into their populations. They have remained unchanged. The Basques are an ancient people whose origins are still a mystery. The Basque language, the only western European language not connected by Indo-European roots, appears to be related to several dialects found in small isolated populations in the valleys of the Caucasus Mountains. Although they look much like their French and Spanish neighbors, Basques possess the lowest frequency of blood group B---originally having no group B at all---and the highest frequencies of blood group O in Europe. Cattle, abundant on the European plains, and fresh water fish seem to have been the staples of their early existence, as evidenced by the extraordinary renderings of the famous cave paintings found in the Basque country. More than fifty percent of the Basque population is Rh negative, as opposed to sixteen percent for the rest of Europe. Like the gene for group O, the genetic mechanism for the Rh negative blood type is simpler, hence undoubtedly older, than the gene for Rh positive. Native Americans are another example of the "old peoples" existing in our world today. It has often been asserted that all full-blooded American Indians are group O, and recent studies on largely intermingled Amerindian populations show a very high (sixty-seven to eighty percent) predominance of O, indicating that their migration from Asia to Alaska was probably much earlier than previously believed.(7,8) Their high rate of blood group O suggests that the Amerindians and Eskimos are directly descended from Cro-Magnon ancestors, probably Mongolians, who migrated around 15,000 B.C. to the Americas. In contrast to the Basques, however, the Asian Amerindians must have mingled extensively with other Asian populations, picking up along the way the gene for Rh positive blood. As with the Basques, few Native Americans are group B, so they must have migrated to the Americas late enough to pick up the Rh positive gene, but too early to pick up the gene for B. (9) This migration probably took place across the land bridge that at one time connected Siberia to Alaska. As the last Ice Age ebbed and the lands warmed and glaciers receded, the rising water levels eliminated the land bridge between Asia and American, bottling up the Native Americans and a high-O enclave and preventing for another 10,000 years any communication between the continents. Forensic studies support this theory: in Chile no B or AB have been noted either in pre-Columbian or Colonial mummies. (19) Another theory for the extremely high incidence of blood group O in Native Americans is that O individuals seem relatively resistant to syphilis and smallpox, major killers of Native Americans that were introduced into the Old World by Columbus. (22) Agricultural advances in the Americas were late in coming, because the new American homeland was abundantly populated with game and fish, which discouraged agriculture. Even corn, which was the staple grain, didn't appear to be domesticated until 4500 B.C., and common beans appear to be an even more recent addition, first being cultivated around 2200 B.C. So, like the Basques, meats and not grains were the primary staple of the Native American diet. In England, Wales and Scotland there is a strong association between ABO blood group and geographical differences in the death rate (10) Studies of blood group distribution in the British Isles show a general increase of group O frequency from relatively low numbers in southern England to increasingly higher ones in northern England, Wales, Scotland, and Ireland. (11) This suggests that the Anglo-Saxons had relatively high A levels, and that O increased as the proportion of Celtic ancestry increased, although the origin of the high incidence of blood group O in the Irish may represent the remnants of Mesolithic peoples. (23) This is also the case with continental Europe, where the percentage of group O increases in northern Germans and Danes. It is also known that the Icelanders had high O frequencies, close to those frequencies found in the populations of Scotland and Ireland. Among the Nomads of the Arabian Peninsula, and the Berbers of the Atlas Mountains, two old populations, the frequency of the blood group O gene is high. Africans, on average, have more O genes and less A genes than do Europeans. So it can be seen that the gene carried by people who are blood group O is ancient by evolutionary standards. Also if you want to know about eyes that change colour look here: http://genetics.thetech.org/ask/ask126 http://en.wikipedia.org/wiki/Eye_color.