Carl Zimmerman‘s article at Ars Technica offers a useful precis.
Why do 40 percent of Caucasians have Type A, while only 27 percent of Asians do? Where do different blood types come from, and what do they do?
To get some answers, I went to the expertsâ€”to hematologists, geneticists, evolutionary biologists, virologists, and nutrition scientists. In 1900, the Austrian physician Karl Landsteiner first discovered blood types, winning the Nobel Prize for his research in 1930. Since then, scientists have developed ever more powerful tools for probing the biology of blood types. Theyâ€™ve found some intriguing clues about blood typesâ€”tracing their deep ancestry, for example, and detecting influences of blood types on our health. And yet I found that in many ways, blood types remain strangely mysterious. Scientists have yet to come up with a good explanation for their very existence.
â€œIsnâ€™t it amazing?â€ says Ajit Varki, a biologist at the University of California at San Diego, â€œAlmost a hundred years after the Nobel Prize was awarded for this discovery, we still donâ€™t know exactly what theyâ€™re for.”
I’m Type O, RH positive myself.