… 45,000 ago.
Passed on by Michael Palmer, from PastHorizons: adventures in archeology, “Mammoth injuries indicate humans occupied Arctic earlier than thought” (from the 15th):
The carcass of a frozen mammoth with signs of weapon-inflicted injuries suggests humans were present in the Eurasian Arctic ten millennia earlier than previously thought. These results, which provide perhaps the oldest known story of human survival in the Arctic region, date human presence there to roughly 45,000 years ago, instead of 35,000 years ago, as previously thought.
Sergey Gorbunov excavating the mammoth carcass. Pitulko et al., Science (2016)