Then what limited the growth of forager peoples so substantially? There had to be a mechanism to prevent them from exceeding their region's carrying capacity. If a tribe of 50 people grew at a rate of 1% for 2000 years there would 24 billion people in it. Clearly that didn't happen; in fact there have been massive die-offs from starvation due to cyclical climate change, or to resource warfare (sometimes fought to extinction) between neighboring tribes.