Why are there so many antigens
How did the different blood groups come about?
What exactly are blood types?
It is mainly about the red blood cells, more precisely about their cell surface. Certain proteins, the so-called antigens, adhere to the blood cells. The blood groups are named after them. If someone has blood group A, then the antigens adhere to the blood cells than in the blood of someone with blood group B. And blood group 0 simply means: neither ... nor. Neither antigens A nor B are attached to the blood cells. However, our body defends itself against foreign antigens that it does not know - therefore, when donating blood, attention is paid to the blood groups, because otherwise the recipient's body will reject the donor's blood.
How did these different blood groups come about?
If you look at the distribution pattern of blood groups around the world, all blood groups appear practically everywhere today, but there are certain ones Clusters:
- Blood group 0 occurs more frequently in Africa and America
- Blood group A in Europe
- Blood group B in Asia
These are rough patterns. How this came about is still being researched. But what has already been well researched is the impact of malaria. This example shows how science basically imagines the evolution of blood groups.
Why blood group 0 has become more prevalent in Africa
It can be reconstructed that blood group 0 evolved from blood group A through an original genetic defect. So: A was there first, then when copying the genetic material there was an error at a certain point, a mutation. The result were people with blood group 0. It all happened at a time when our ancestors still lived in Africa. (Actually, they weren't "humans" in today's sense, but at most pre-humans.)
As is well known, there is now malaria in Africa. And it has been found that carriers of blood group 0 cause malaria, especially the dangerous ones Malaria tropica, have higher chances of survival. This is because the pathogen cannot multiply so quickly in these people's blood. With malaria it's a bit like Covid-19 - people with blood group 0 seem to get away with it more lightly.
A process spanning millions of years
The difference is that malaria has been around for millions of years. If people with blood group 0 have even a slightly increased chance of survival in malaria areas, this has meant that the blood group has become more and more prevalent in Africa over time. This is especially true for the humid tropical areas: the Niger Delta is a prime example. There the proportion of blood group 0 in the population is very high. In other parts of the world where malaria does not play such a big role, however, blood groups A and B have remained.
Other pathogens also play a role
This influence of the malaria pathogen does not fully explain the evolution of the blood groups - certainly not the distribution of A and B. However, this effect has been studied so well that one can assume that pathogens in general are the decisive factor in the development of different blood groups and their distribution if they have favored the carriers of one or the other blood group.
Are there also different blood groups in animals?
Yes, there is such a thing as blood groups in animals too. The AB0 system is also known from other primates - it is older than humanity. In addition to A, B and 0, we also differentiate between the so-called Rhesus factor in humans. It is called that because it was originally found in the rhesus monkey.
Different blood groups have also been detected in fish. But then these are not the blood groups that we know - A, B and 0 or the Rhesus factor - but completely different types than in humans.
The text and audio of this post are licensed under the CC BY-NC-ND 4.0 Creative Commons license.
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