Modern Human Variation: Distribution of Blood Types
Distribution of Blood Types
Blood   provides an ideal opportunity for the study of human variation without    cultural prejudice.  It   can be easily classified for many different genetically inherited blood typing systems.  Also significant is the fact that we rarely take blood types into consideration in   selecting mates.  In addition, few people know their own type today and no one did prior to 1900.  As a result, differences in blood type frequencies around the world are   most likely due to other factors than social discrimination.  Contemporary Japan is somewhat of an exception since there are popular    Japanese stereotypes about people with different blood types.  This could affect choice in marriage partners for some Japanese.
All human   populations share the same 29 known blood systems, although they differ in the frequencies of   specific types.  Given the evolutionary closeness of apes and monkeys to our species,   it is not surprising that some of them share a number of blood typing systems with us as   well.
When we   donate blood or have surgery, a small sample is usually taken in advance for at least ABO
and Rh
systems typing.  If you are O+, the O is your ABO type and the + is   your Rh type.  It is possible to be A, B, AB, or O as well as Rh+
or Rh-
.  You inherited your blood types from your parents and the environment in which you live cannot   change them.
 
ABO Blood Type System
We have learned a good deal about how common each of the ABO blood types is around the world.  It is   quite clear that the distribution patterns are complex.  Both clinal and discontinuous distributions    exist, suggesting a complicated evolutionary history for humanity.  This can be seen with   the global frequency patterns of the type B blood allele (shown in the map below).  Note that it is highest in Central Asia and lowest among the   indigenous peoples of the Americas and Australia.  However, there are   relatively high frequency pockets in Africa as well.  Overall in the   world, B is the rarest ABO blood allele.  Only 16% of humanity have it.
Distribution of the B type blood       allele in native populations of the world
The A blood allele is somewhat more common around the world than B.  About 21% of all people share the A allele. The highest frequencies of A are found in small, unrelated populations, especially   the Blackfoot Indians of Montana (30-35%), the Australian Aborigines (many   groups are   40-53%), and the Lapps, or Saami people, of Northern Scandinavia (50-90%).  The A allele   apparently was absent among Central and South American Indians.
Distribution of the A type blood       allele in native populations of the world
The O blood type (usually resulting from the absence of both A and B alleles) is very common around the world.  About 63% of humans share it.  Type O is particularly high in frequency among the indigenous populations of Central   and South America, where it approaches 100%.  It   also is relatively high among Australian Aborigines and in Western Europe   (especially in populations with Celtic ancestors).  The lowest frequency   of O is found in Eastern Europe and Central Asia, where B is   common.
Distribution of the O type blood         in native populations of the world
 
Other Blood Type Systems
The   majority of the people in the world have the Rh+ blood type.  However, it is   more common in some regions.  Native Americans and Australian Aborigines   were very likely 99-100% Rh+ before they began interbreeding with people from other parts of the world.  This does not imply that Native Americans and Australian Aborigines are   historically closely related to each other.  Most Subsaharan African populations are around 97-99% Rh+.  East Asians are 93-99+% Rh+.  Europeans have the lowest frequency of this blood type for any continent.  They are 83-85% Rh+.  The lowest known frequency is found among the Basques of the Pyrenees   Mountains between France and Spain.  They are only 65% Rh+.
The distribution    patterns for the Diego
blood system are even more striking.  Evidently, all    Africans, Europeans, East Indians, Australian Aborigines, and Polynesians are    Diego negative.  The only populations with    Diego positive people may be Native Americans (2-46%) and East Asians (3-12%).  This nonrandom distribution pattern fits well with the hypothesis of an East    Asian origin for Native Americans.
Conclusion
These patterns of   ABO, Rh, and Diego blood type distributions are not similar to those for skin color or other so-called "racial" traits.  The implication is that the specific causes responsible   for the distribution of human blood types have been different than those for other traits   that have been commonly employed to categorize people into "races."  Since   it would be possible to divide up humanity into radically different groupings using blood   typing instead of other genetically inherited traits such as skin color, we have more   conclusive evidence that the commonly used typological   model for understanding human variation is scientifically unsound.
The more we study the   precise details of human variation, the more we understand how complex are the   patterns.  They cannot be easily summarized or understood.  Yet, this   hard-earned scientific knowledge is generally ignored in    most countries because of more demanding social and   political concerns.  As a result, discrimination based on presumed "racial" groups still continues.  It is important to keep in   mind that this "racial" classification often has more to do with cultural   and historical distinctions than it does with biology.  In a very real   sense, "race" is a distinction that is created by culture not biology.