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In September 23andMe produced a study showing that subjects belonging to blood group O (the most common type in Europe) have a slightly reduced chance of developing covid: https://blog.23andme.com/23andme-research/blood-type-and-covid-19/
This is not the first time a blood group has been found to affect infectious disease risk. Maybe the most well-known example is that O carriers have a doubled chance of developing cholera, against which AB is almost miraculously protective: https://academic.oup.com/aje/article-abstract/121/6/791/92191
The historic epicenter of cholera is the Ganges River Delta in and around Bangladesh. As a result of selective pressure, people in the Delta have the world’s lowest frequency of blood group O (American Indians have the highest, in some cases 100%) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4367964/
This is the really interesting thing about blood groups: you can read a population’s recent history of disease by examining their groups: e.g. O is protective against malaria, which helps explain its high frequency in Africa, the Gulf Coast, and Sicily: https://en.wikipedia.org/wiki/Blood_type_distribution_by_country
A person could write a PhD thesis explaining the historical basis of the relatively unusual blood group frequencies just in Armenia/Japan/ Mongolia, but what I find most interesting is the enormous difference between East and West Europeans.
I’ll just outline the problem and see if someone else can figure out what I couldn't. O is the plurality group in Western Europe with a peak frequency of around 55% in Iceland, Ireland, and the Basques. But Slavs have some of the lowest frequency of O on Earth.
The point is, one or the other of us have changed, man. The fact that O is the oldest blood type, almost universal in American Indians and in isolated Europeans makes me think it was once more common and that it was Easterners who have been under more recent selective pressure.
But not just Slavs, because Norwegians also have a dramatically reduced frequency of O compared to Icelanders, who are around 75% Norwegian. JBS Haldane noticed this in the 30’s and drew the false conclusion that Icelanders were largely descended from Irish slaves.
The basic problem: I _think_ there has been a disease or diseases moving into Europe from Asia in the last 2,000 years that has affected East Europeans much more than Westerns and has affected the Icelanders, Irish, and Basques least of all. What is it?
If it was cholera that would explain a lot, but the first major European cholera epidemic didn’t happen until 1821, which seems far too late to have this kind of effect. 4000 Twitter points to whoever can figure it out first.
