This is a subject matter where we may be tainted by common consent dominating the Google results with suggestions that blood type O was the first blood type that humans or humanoids have had in this world.
The truth of the matter is that there is no proof that blood type O, or any other blood type for that matter, was the first blood type.
There are however many indications out there that blood type O was NOT THE FIRST, but rather a result of ongoing evolution.
Because group O blood can be received by anyone in a blood transfusion, it was originally thought that this was the ancestral blood type, but more recent work suggests that there are several different mutations that can deactivate the A or B genes to turn them into O. This makes a firm timeline much harder to establish and there are several competing theories that contradict each other. What they agree on is that AB is the most recent and didn’t occur until the 16th century when group A populations from Europe and group B populations from Asia began to mix. The other blood groups are tens of thousands of years old with B being more recent than A. The oldest group is either group A or one of the forms of group O.
The evolution of human blood groups, without doubt, has a history as old as man himself. There are at least three hypotheses about the emergence and mutation of human blood groups. Global distribution pattern of blood groups depends on various environmental factors, such as disease, climate, altitude, humidity etc. In this survey, the collection of main blood groups ABO and Rh, along with some minor groups, are presented. Several investigations of blood groups from Iran, particularly a large sampling on 291857 individuals from Iran, including the main blood groups ABO and Rh, as well as minor blood groups such as Duffy, Lutheran, Kell, KP, Kidd, and Xg, have been reviewed.