A 4000-year-old major discovery: How blood types were discovered.

　There is a term called Columbus' Egg.

　It's simple once our understand it, but this phrase expresses the difficult of focusing on something simple.

　For such a long time, something simple, yet no one paid any attention to, was Blood Type.

　Humanity knows from experience that excessive bleeding can kill people and animals.

　Blood Transfusions, a way to replenish blood, have been around since ancient Egypt and Rome. However, at the time, people believed that they could replenish blood by drinking the blood of other people or animals.

　The method of injecting blood directly into a vein was first used in France in the 17th century. The blood used was sheep's blood. Naturally, the patient died, and blood transfusions were subsequently banned as a dangerous treatment.

　In the 19th century, blood transfusions were used again.

　At that time, the concept of blood types did not yet exist.

　If the blood type is different, a rejection reaction will occur and the patient will die. In fact, blood transfusions have a low success rate and were the last resort for patients who would die from excessive bleeding if left untreated.

　A major turning point is coming for transfusion treatment.

　Landsteiner, an Austrian doctor from the late 19th century, administers a blood transfusion to a patient.

　Some patients survived, but others died a few days later due to rejection. Landsteiner focused on the fact that this was a common occurrence in blood transfusion treatment and that many people did not even think about it.

　What was the difference between the patients who were saved and those who were not?

　At the time, advances in machinery, laboratory equipment, chemicals, and everything else were happening, and there was a growing trend to scientifically verify things.

　The background of the times may have also been a factor. He noticed that when one person's blood was mixed with another person's blood, the red blood cells would clot.

　In 1900, he investigated the cause of blood clotting and discovered that the Antibody Components in blood differ from person to person.

　He discovered that there are four types of blood types in humans: Type A if you have the component of antibody A, Type B if you have antibody B, Type AB if you have both antibody A and B, and Type 0(Zero) if you have none. Type 0 later came to be known as Type O.

　It was discovered that red blood cells do not clot if both blood types are the same, making blood transfusions a safe treatment method.

　When we think of blood types, we think of personality and compatibility fortunetelling.

　The relationship between blood type and personality was investigated by many doctors and psychologists in Europe in the 20th century. The conclusion was no correlation.

　In Japan, the Japanese army took notice of this in the early 20th century, and military doctors investigated it.

　At that time, Japan had a conscription system. Training soldiers was time-consuming and costly.

　They thought that if they could find out which blood type was suitable for soldiers and conscript young people with that blood type, it would be more efficient. The results of their research showed that Type B is suitable for soldiers. This is based on the survey results that Type B people are courageous and courageous.

　But after further testing, it turns out that this is incorrect.

　Just like today's Accurate Fortune Telling, this is the conclusion of the Barnum Effect, which links Abstract Words that apply to everyone with Matching Actions and Statements and makes people feel that their predictions are accurate.

　By the way, Columbus' Egg is called Columbus' Egg Stand in Chinese.

　The word has its origins in the West, so it is the same as in Japanese, but the word Columbus' Egg is not widely understood in the West.