Blood Types: History, Genetics, and Percentages Around the World
Blood type is determined by sugar-based antigens on the red blood cell surface. Those with type O blood do not have any antigens at all.
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What Is Blood Type?
Prior to the discovery of blood groups, blood transfusions were often deadly. Physicians attempted the use of milk and animal blood as an alternative to human blood but met with limited success: the discovery of blood types allowed modern transfusions to safely take place.
Red blood cells (called erythrocytes) have a type of antigen on their surface. Composed of sugar molecules, these antigens are called agglutinogens. There are two types of agglutinogens: type A and type B. The type of antigen on the surface of your red blood cells determines your blood type.
There are four basic blood types, made up from combinations of the type A and type B antigens.
Type A: The red blood cells have the type A agglutinogen.
Type B: The red blood cells have the type B agglutinogen.
Type AB: The red blood cells have both type A and type B agglutinogens.
Type O: The red blood cells do not have any agglutinogens at all.
There is another protein (called Rh factor) that is sometimes found on red blood cells. If a person has Rh factor, their blood type is called “Rh positive.” An individual lacking this protein is called “Rh negative.” Combined with the ABO blood types described above, a person may be A+, A-, B+, B-, AB+, AB-, O+, or O-.
Blood Types Around the World
Blood types vary depending on the geographical region: Scandinavians have a high probability of carrying the A blood type, while those indigenous to central Asia are more likely to carry the B blood type. The O blood type is the most common blood type around the world.
According to the National Center for Biotechnology Information (a molecular biology resource funded by the government), the breakdown of blood type by region is:
Blood Type A: Central and Eastern Europe
The A blood group is common in central Europe. Nearly half the population in Denmark, Norway, Austria, and Ukraine have this blood type. This blood type is also found in high levels among small, unrelated groups of people. In Montana, 80% of the Blackfoot tribe has the A blood group.
Blood Type B: Asia
The B blood type is rare in Europe (about 10% of the population), but fairly common in Asia. Nearly 25% of the Chinese population demonstrates this blood type. This blood type is also fairly common in India and other Central Asian countries.
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Blood Type AB: Asia
The AB blood type is the rarest of all. It is found in up to 10% of the population in Japan, Korea, and China, but is extremely rare in other regions.
Blood Type O: The Americas
The O blood type is the most common around the globe and is carried by nearly 100% of those living in South America. It is the most common blood type among Australian Aborigines, Celts, those living in Western Europe, and in the United States.
Rh Factor
The majority of people in any geographical region are Rh positive. Caucasians are the most likely to be Rh negative, with approximately 17% of blood donors demonstrating a lack of this protein. Native Americans are the next highest proportion of the population to test as Rh negative: approximately 10% of donors from this population lack this protein.
Coconut Juice Blood Transfusions in World War II
As World War II raged through the Pacific, blood products were in short supply. In emergency situations, Japanese and British medics would resort to coconut water. Coconut water (the juice inside a young coconut, not "milk" which is made from grinding up the meat of the fruit) has fewer electrolytes than blood plasma, but it is sterile and works in a similar manner to a saline IV drip. In a pinch, coconut water is tolerated fairly well by humans. In fact, coconut water preserves teeth better than milk—something to keep in mind the next time a tooth gets accidentally knocked out!
The History of Blood Transfusions
In the 19th century, no one understood that people had different blood types. Blood transfusions often resulted in death, as the receiver's immune system would attack the foreign, unmatched blood that was transfused.
The history of blood transfusion goes all the way back to the 1600s when William Harvey discovered the circulatory system. By 1658, Jan Swammerdam was viewing red blood cells through a microscope. The very first transfusions occurred in dogs, as the English physician Richard Lower demonstrated that a dog could be kept alive by transfusing blood from other dogs.
Unfortunately, the move to human transfusion was quite tricky. As there was no understanding of blood groups, blood transfusions were extremely risky. Sometimes they were successful: in 1818 James Blundell managed to accomplish the first successful human blood transfusion and saved a woman hemorrhaging from childbirth. Other people, however, simply went into shock and died after blood transfusions.
Some scientists attempted to prevent the adverse reactions to blood transfusions by transfusing blood substitutes. The transfusion of cow’s milk was attempted in 1854 in Canada, during a cholera epidemic. Drs. Bovell and Edwin Hodder started intravenous transfusions of milk in the belief that the fat molecules in milk could be transformed into white blood cells, and that white blood cells were an immature version of red blood cells. This belief was erroneous, of course, but they had success with one sick man who responded favorably to the transfusions. Two other patients, however, died after milk was transfused into their veins.
These experiments were discontinued in Canada shortly after the cholera epidemic but were revived in New York City a few years later. Using goat’s milk this time, Dr. Joseph Howe transfused patients suffering from terminal tuberculosis. The patients all demonstrated nystagmus (shaking eye movements) and chest pain, and all of the patients died a few hours after transfusion.
Despite the lack of obvious benefit, milk transfusions continued in the late 1880s, as the use of blood was discouraged since it had a tendency to coagulate. As more patients died from milk transfusions, the practice fell out of favor. In the 1880s, isotonic saline solution was invented, and the use of milk fell entirely out of favor in favor of the new, safe saline solution. The revival of blood transfusions would have to wait for the 20th century when a new era of microbiology ushered in the understanding of various blood groups and compatibility.
In 1901, an Austrian doctor named Karl Landsteiner recognized the three basic blood groups—blood was first cross-matched in 1907. Blood storage was still a problem during the early days of blood transfusion—while the compatibility issues had been resolved, blood still had a tendency to clot during storage. Anticoagulants like sodium citrate were developed in the year 1914, allowing blood storage for an extended period of time. The discovery of Rh factor in 1940 allowed doctors to completely understand the compatibility issues among blood donors and recipients, and the American government started its first national blood collection program shortly thereafter.
Blood Type Tests and Blood Transfusions
A traumatic car accident has occurred, and a severely injured patient is rushed to the emergency room. As the patient lies bleeding, doctors scurry to take a sample of the patient’s blood and have it sent away to be typed and cross-matched.
In the laboratory, a technician applies the blood to a special card, which contains antibodies to the A and B blood groups. If the patient’s blood clumps around the A antibody, this means they have the B antigen and it is attacking the A antibody. If the patient’s blood clumps around the B antibody, then the patient has the A blood type. If the patient’s blood clumps around both the A and the B antibodies, they have the O blood type, and if the patient’s blood doesn’t react to either the A or B antibodies, then he or she has the AB blood type.