Even with the abundance of plant and animal food, they were preoccupied with survival. There were too many things to be taken care of: avoiding falling prey to carnivores (including fellow humans), injuries, sickness; need to hunt and/or collect food, tend to children. There was just no time to think about much else. But the prehistoric form of communism made survival easier. In the later, more individualist, times, if you wanted to be able to spend time and your thoughts on something other than mere subsistence, you had to have servants.