I believe the ice age caused the people alive and struggling to eat, sleep, mate and get by... to gather with others and migrate to warmer climates. It sounds like the ice age had perhaps one good effect.... people learned to get on the move, and to have to place some trust in gathering together. In the struggle to find any kind of food - be it plant, fish or a tiny animal left -- they most probably learned somewhat the art of and benefit of cooperation. Life was very hard and procreation probably did not occur much until the people found a warmer climate.