Blood type variations originated from common primate ancestors around 20 million years ago. While blood transfusions between species, such as between apes and humans, are not viable due to different and incompatible blood antigens, the development of blood type systems, including types similar to the human A, B, AB, and O, can be traced back to these early ancestors.

This evolutionary milestone, involving the presence or absence of specific antigens on red blood cells, provided a crucial adaptive advantage against various pathogens. As primates branched out and occupied diverse ecological niches across continents, these genetic variations became instrumental in their survival. This trait underscores the evolutionary processes that contribute to the vast genetic diversity seen across primates, including humans, demonstrating how adaptations to local environmental pressures can drive evolutionary change across millions of years.