How did blood types evolve?

The ABO blood group evolved at least 20 million years ago, but scientists still don't understand the purpose of blood types. read more

Blood types are primarily dictated by sugar decorations on proteins. Specifically, N-acetylgalactosamine for the A-type and galactose for the B-type. The O type is the complete absence of either sugar decoration. read more

Blood banks run blood type tests before blood is sent to hospitals for transfusions. Image: U.S. Navy photo by Mass Communication Specialist 3rd Class Jake Berenguer/Wikicommons Everyone’s heard of the A, B, AB and O blood types. read more

Blood type A is the most ancient, and it existed before the human species evolved from its hominid ancestors. Type B is thought to have originated some 3.5 million years ago, from a genetic mutation that modified one of the sugars that sit on the surface of red blood cells. read more