CAN EXPLAIN A NEW PHENOMENON TAKING PLACE IN OUR BLOOD?

HELP SCIENTISTS SOLVE ONE OF THE GREATEST MYSTERIES HUMANS COULD BE FACED WITH IN MODERN TIMES. IT IS BAFFLING. IT'S GOT ME STUMPED. IT HAS TO DO WITH OUR BLOOD. IT'S ON THE TIP OF MY TONGUE BUT I CAN'T QUITE GET IT OUT. CAN YOU?