It was a safety net against poverty for people over the age of 65, as well as being a welfare system for disabled people.
Option 'B' = changes in climate, had the greatest impact on pre-historic man.
Changes on the weather forced men to move periodically or cyclically, usually returning to their original location at various times. When they moved to colder climates, they would make clothing out of animal skins, to protect themselves. When the nomads learned how to plant, they didn't need to search for other places anymore.
