Throughout the history of mankind, the world has experienced various epidemics and pandemics many times, but few people know what consequences they brought with them, and how they continue to affect our lives today.
A prime example would be, presumably, the malaria pandemic, which affected a huge part of the world about 2 million years ago. Throughout this period, sialic acid producing species gradually died out. The reason for the sharp extinction of the species was a pandemic, the pathogens of which used sialic acids to invade the cell (now the malarial plasmodium, which affects chimpanzees, has the same mechanism of action).
For those who survived the pandemic, it had enormous consequences. Their cells stopped producing Neu5Gc. This means that they could no longer conceive offspring with a subject unaffected by the pandemic. Their body accepted the cells of the embryo as foreign and destroyed. Thus, the survivors could reproduce only among themselves and drove out the species without the mutation that took part in the victory over the disease.
So why does it matter so much?
The point is that a massive gene mutation should lead to the birth of a new species. According to the official data, it was around this time that the first erect hominid appeared. Amazingly, it turns out that the malaria pandemic could have contributed to the birth of the human species.
How does this affect the world today?
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If you study different peoples, and parts of the Earth, depending on where they live, people have a different genome, which suggests that pandemics have occurred in different parts of the planet, contributing to the separation of certain species and stimulating their evolution in different directions.
Now a person can feel the consequences of pandemics in their own experience. About 5% of miscarriages are due to the body recognizing some mutations as containing the pathogen and discarding the fetus. Eating red meat can stimulate the development of various diseases, precisely because it contains the very sialic acid that the body considers hostile and begins to fight it with the help of inflammation, which can increase the risk of certain diseases. There are hundreds of such examples.
It turns out that the change in the genome, which helped us, once to preserve our species, in some cases can lead to tragic consequences today. Thus, pandemics are of great importance both in human evolution and in fundamental changes in their genome, the consequences of which may become an important problem millennia after the defeat of the pathogen.