I checked on this 'indicator', here's what is said on page 245 of the book, Tarim Mummies.
"...although our data is extremely restricted, so far it suggests that prehistoric Xinjiang was a good area for transfusions: all the mummies so far examined have been revealed as universal donors ,i.e. type O. Blood typing has been carried out on the 'Beauty Of Kroran' from the cemetery on the Towan River and three of the female mummies from Qizilchoqa also possessed blood type O."
Like I said, they were Celts, but science doesn't get it and are not likely to any time soon, but generally Celts the world over get it.And in time one of us will write the truth.