Everyone’s heard of the A, B, AB and O blood types. When you get a blood transfusion, doctors have to make sure a donor’s blood type is compatible with the recipient’s blood, otherwise the recipient can die. The ABO blood group, as the blood types are collectively known, are ancient. Humans and all other apes share this trait, inheriting these blood types from a common ancestor at least 20 million years ago and maybe even earlier, claims a new study published online today in Proceedings of the National Academy of Sciences. But why humans and apes have these blood types is still a scientific mystery.
The ABO blood group was discovered in the first decade of the 1900s by Austrian physician Karl Landsteiner. Through a series of experiments, Landsteiner classified blood into the four well-known types. The “type” actually refers to the presence of a particular type of antigen sticking up from the surface of a red blood cell. An antigen is anything that elicits a response from an immune cell called an antibody. Antibodies latch onto foreign substances that enter the body, such as bacteria and viruses, and clump them together for removal by other parts of the immune system.
