I believe that’s totally ridiculous. It would be more believable that a person of type AB, A , or B might type as an O after many years due to degeneration of the antigen protein, but there is no way blood that lacks the A and B antigen somehow mysteriously develops it over time. That theory is a total reach.
Blood types generally have ethnic specificity. Asians tend to be type B, Eastern Europeans type A, and those of Jewish descent AB - totally consistent with authenticity of the Shroud and another strike against forgery How would the forger know the common blood type of a Jewish man when the ABO grouping system was not identified until 1901?
Oh, I agree. I think it’s a big stretch. The are tossing out hypotheses to try and explain why so much old blood is testing AB, though, but frankly, most of the old blood that has been really tested comes from guess where? The Shroud of Turin and the Sudarium of Oviedo, both associate with Jesus. Another one is the Holy Coat of Agincourt, the garment without seams that was supposedly worn by Jesus on the Via Dolorosa carrying his Cross and bleeding from the many wounds of the scourging and the blood dripping from the Crown of Thorns. All have tested as AB. I think there is some blood in a Catholic miracle that is coagulated that converts to liquid blood every specific day which also tests AB. I’m not Catholic, so you can’t prove that by me, but I’ve read that.
Why would they thus hypothesize about other explanations??? I leave that exercise to you. I follow the science. I just listed what scientists are saying and what they are researching. LOL!