Blood is divided into groups based on the presence in it of certain antigens and antibodies to them. There are four main groups: 0( I), A( II), B( III), and also AB( IV).Each of them corresponds to a number, and the letter indicates the absence or presence of specific antigens. This is also an indicator of compatibility.
In humans, the genetic characteristics of the blood do not change during life. This is a specific identifier of the person, which the parents inherit from the children. Groups are more ancient than nationalities and races. The main difference between different people, according to many scientists, is not the ethnic origin and color of the skin, namely in the blood.
The most common blood type is the first. For transfusion, it is the most suitable, because it does not contain antigens. The second is only suitable for people of the same and the fourth group because of the presence of antigens A. The third is suitable only for the owners of the third and fourth, and the last of them can be transfused only to people with the same blood group.
However, the importance is not only the presence or absence of antigens, but also the Rh factor. It is determined by the presence of protein on the surface of erythrocytes. If it is, the Rh factor is positive, and if it is absent, it is negative. About 85% of the world's population have a positive Rh factor. For example, the third negative blood group is much less common than the positive one. The same goes for the rest.
The first, the most common blood type, is found in 45% of the world's population. Next in order are the rest. The rarest group is the fourth. If you take into account the Rh factor, the most common blood group - the first positive, and the rarest - the fourth negative.
Group and Rhesus should be considered during pregnancy planning. If the fetus inherits the parameters of the father, which will be incompatible with the blood of the mother, then during pregnancy problems are possible. However, modern medicine is quite capable of preventing them.
The composition of blood was formed many thousands of years and is associated with the formation of the immune and digestive systems. Blood group 1 was positive in ancient times for all mankind. The digestive tract was then most suitable for digesting meat protein foods. Therefore, people of this category still have high acidity of gastric juice, and they are predisposed to peptic ulcer. The first is still the most common blood type. With the increase in the number of mankind, because of its deficiency, meat became less accessible, so people began to consume the plants more and more. This affected the qualitative composition of the blood, which led to the emergence of other groups that gave people many useful qualities.
For example, blood holders with a gene A are more adapted to life in the modern world. This gene in its time became a guarantee of survival of people during the terrible epidemics of plague and cholera. People with this blood composition are less aggressive and have more contact, which helps them feel good in society.