Ancestry runs deeper than blood: The evolutionary history of ABO points to cryptic variation of functional importance
http://www.pnas.org/content/early/2012/10/17/1210603109.full.pdf
http://bloodjournal.hematologylibrary.org/content/102/8/3035?variant=short&sso-checked=1
http://www.plospathogens.org/article/info%3Adoi%2F10.1371%2Fjournal.ppat.0040002