Blood Types Have Deep Roots: ABO System May Date Back 20 Million Years or More

Article excerpt

Chimps, gibbons and other primates are not just humans' evolutionary cousins; a new analysis suggests they are also blood brothers. Blood types found in people today evolved at least 20 million years ago in a common ancestor of humans and other primates, new research suggests.

The analysis deepens a mystery surrounding the evolutionary history of the ABO blood system, and should prompt further research into why the different blood groups have persisted over time, Laure Segurel of the University of Chicago and colleagues report November 6 in the Proceedings of the National Academy of Sciences.

"Their evidence is rather convincing that this is a shared, very old capability that has remained throughout the divergence of the species," says physician and transfusion specialist Martin Olsson of Lund University in Sweden.

Different forms of a single blood type gene determine what kinds of molecules sit on your red blood cells: type A molecules, type B molecules, A and B together, or no intact surface molecules in the case of type O.

The A, B and O versions of the gene differ only slightly, and scientists have debated two scenarios to explain their evolution. One posits that the A version of the gene existed long ago, and the B and/or O versions later cropped up independently in several species (including humans, gorillas, baboons and chimps). Alternatively, all of those species may have inherited the A and B types from a single ancestor. …