Sowhatnow, in the absence of maestro Cofty, may I say that polar bears and humans are new kids on the block geologically speaking.
We have evidence for Homo sapiens around 100,000 years before present (bp). We have indications for H sapiens existing fifty thousand years before that and therefore it would be assumed in the nature of things that Humans arrived on the scene perhaps more than 200,000 years bp.
The real expansion took place around 40,000 bp when recognizably human cultural artifacts become abundant, things such as spear throwers, bows and arrows, bull roarers, boomerangs, complex stone tools and sewing. This was the start of cave paintings in the Dordogne in France. These people are called Cro Magnon ('Big hole' in translation from the first find location) yet these humans although looking just like us actually had skulls thicker than ours and yet only forty thousand years ago.