<<Disclaimer: Verify this information before applying it to your situation.>> I must confess to having followed this discussion with some interest and being singularly unsurprised about the results. I am speaking way out of my area of competence (if I have one) and from memory. I should really check this but don't know where to look. If I am wrong, I am sure someone will tell me anyway. As I recall it, the world's epicentre for blood group O is Scandinavia. Thus people with an ancestry which is Northern European tend to have this group. Blood group A is (as far as Europe is concerned) more Mediterranean. Thus, in Southern England group A (as in my case) predominates but in the North East of England with its predominantly Scandinavian ancestry, group O predominates. I imagine that Wheat would be difficult to cultivate in Northern European climes and so the populace ate rye and oats as their staple diets whereas the Southern Europeans ate more wheat. Of course, Ireland (along with Scandinavia (I think) is the world's epicentre for Coeliac type disorders but I have no idea what blood group predominates. There is a big Danish contribution around the Dublin area though. I can't help thinking that the co-incidence of blood group O with Coeliac conditions is just that: a coincidence rather than one being causative of the other. These epicentres correspond with what were historically non wheat eating areas rather than the blood groups. As some of you know, our main research area is autism and the possible role of gluten and casein in its causation. We always check out the ethnic and geographical ancestral histories for this very reason. We have not asked for blood groups but perhaps we should. I may have got this wrong and if so I hope that someone will correct me and stop me from saying it again!! Paul Shattock (A+)