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Natural selection is an inherent aspect of human evolution that is responsible for human ethnicity. Over time, biological aspects pertaining to blood groups have been cited to have impacted greatly on early migrations and relative ethnicity. In addition, the differences in race can partly be attributed to blood groups. Most importantly, infectious diseases have had significant impacts on human evolution and the process of natural selection. In this regard, persons with genes that are resistant to different diseases typical of a given geographic area tend to be more likely to settle in the region than their counterparts. This is because they are often more tolerant and resistant to infections that are typical n the given region. For instance, the bubonic plague that affected Europe in the early years was essentially caused by bacterial infections. Historic trends showed that persons that contracted it in early years were more susceptible to death than their counterparts who contracted them in later years. This is because with time, populations developed traits that enhanced their immunity against the diseases. Persons with blood group O suffered more fatalities but on development of ABO blood groups, their immunity was boosted. Population patterns indicated that resistance of early plagues was higher in regions that were inhabited with persons with blood group A as opposed to those with blood group O.

Also worth mentioning is the relationship between malaria and blood groups. As the society progressively embraced Agriculture, malaria became an endemic disease as clearance of trees paved way for frequent pools of water. This increased the incidences of malaria in different regions. In this regard, persons with blood group O had a higher survival rate than their counterparts. Essentially, it is agreed that persons with blood group O tend to be more resistant to flukes, worms and a wide range of parasitic diseases. This is because it is the only blood group that has antibodies against antigens A and B. This can be used to explain why persons with this blood group usually inhabit tropical regions. At this point, it can be acknowledged that the ascent of humans to the top of the food chain can be attributed to the blood group O. On the other hand, urbanization and change to a concentrated lifestyle was contributed to by attributes of blood group A. Blood group A enabled populations to tolerate and assimilate Agricultural products in addition to the sedentary lifestyle. Thus most persons with this blood group can be found in concentrated and urbanized parts of Europe. Further, migration of humans from their homeland to parts of Asia and Europe was contributed to by blood groups AB and B. This is because they lacked the essential blood group O that would boost their resistance to tropical diseases that were mainly parasitic in nature. Thus blood group O is the simplest and most ancient blood group that preceded all other blood groups. Most native societies such as the Basques have this blood group, regardless of the fact that they are found in Europe. In addition, the high incidence of this blood group amongst conventional societies in Europe can be explained by its resistance to diseases such as small pox and syphilis. Notably, these were the causes of major deaths in Europe during the era of Columbus.