It has been argued that the extinction of large game was a consequence of the terrific hunting skills possessed by these migrating Asian hunters, but other evidence points to changes in the vegetation at the end of the last glacial period.
Originally forest hunters advancing and retreating along the outskirts of the boreal and tropical woodlands with each change in climate, Hunter Geno Types are acutely tuned and flexible in their reactions, which perhaps explains why as a human technology they have been so historically successful – and why they continue to adapt to new conditions and challenges.
In their ultimately failed attempts to do so, these large mammals began to migrate east with the shrinking tundra forcing upon these early Homo sapiens one of two choices: Stay put or keep moving west and come to terms with the encroaching forest, or move eastward with the large mammals.
Those who stayed became the hunter-gatherers of the forests and fishers of the numerous rivers, bays, and shallow waters connected to the seas of Europe.
If you need a quick metaphor for the Hunter metabolism, just think of those turn of the century steamships with their glowing coal furnaces buried deep down inside of the hull of the ship.
In North America, the dominant feature was the presence of a vast ice sheet almost completely covering Canada.