A long time ago, in the unpublished manuscript of a book on evolutionary biology, I put forward a hypothesis for the origin of blood group antigens that correlates with recent medical findings in relation to the ABO blood group system. My scenario is based upon interactions between invading organisms (whether viral, bacterial, protozoan, or multicellular) and their hosts.

It is now well known that pathogens and parasites can insert DNA sequences into their hosts‟ genomes (or otherwise genetically manipulate them) in order to enhance their own survival, and it is becoming more and more obvious that human beings are just as susceptible to these strategies as are other species.