According to the paper’s lead author Albert Zink:
The fact that we found some of the fibrin [a protein that is part of the blood clotting process] confirms that he didn’t survive the arrow for a long period. It’s good to have, because there were still some people [thinking] that maybe he could have survived the arrow shot for a few hours, a few days.
Zink, a biological anthropologist at the European Academy of Bozen/Bolzano, says that the arrow severed the man’s arteries in such a way that it caused his death within minutes of contact. Ötzi, the name given to this Bronze Age human discovered frozen in the Alps between Austria and Italy, was believed believed to have died from a strike to the head.
The researchers, though, were able to find complete blood cells in Ötzi’s body and around the arrow wound entrance using a new technique. First they found round objects using a light microscope. Their shape looked like red cells but they couldn’t really tell what they really were. Then they used an atomic force microscope to create a three-dimensional model of the object. The result greatly surprised Zink and his team: they were complete red cells.
It was very surprising, because we didn’t really expect to find compete red blood cells. We hoped to find maybe some remnants or shrunken red blood cells, but these are looking like a modern-day sample; the dimensions are the same.