QUESTION: I have read that Scots, Irish, Icelanders (despite their predominantly type A Norwegian forefathers) and Basques are the European populations with the highest incidence of type O blood -- can you recommend any reputable or otherwise authoritative source that could explain this and any other question of blood type distribution by geography or nation?
ANSWER: The best book that one can still purchase (most of the early works are long out of print) are the works of A.E. Mourant and a few others. These include:
1. "The distribution of the human blood groups, and other polymorphisms" by A. E. Mourant by Oxford Press
2. "Blood Relations : Blood Groups and Anthropology" by A.E. Mourant by Oxford Press
3. "History and Geography of Human Genes" by LL Cavalli-Sforza by University Press.
4. "Races and Peoples" by Isaac Asimov and William Clouser Boyd by Harcourt
These works are not easy to find, although you can check with your local university library, who may have them in the Reference section. You may also want to try the various electronic and paper Encyclopedias. These sections on blood types and/or anthropology almost always feature population frequency maps of the various ABO groups.
They might take issue with your categorization of the predominantly Celtic Scots and Irish as having 'Norwegian forefathers" however.