To close it up:
Cro-Magnons may have had higher percentages of Rh- blood, but that would have been due to higher percentages of DNA from the Rh- source:
The Neanderthals.
Neanderthals were a separate species.
Cro-Magnons were hybrids.
Cro-Magnons would have had less Rh- %s than most human populations today, but likely less than the Neanderthals at the time when they evolved from Partial D towards a complete D gene deletion.