Well they not have realised that Co2 & only Co2 controls the climate.
They must have stopped burning poo & wood for it to get that cold (& eating the food raw).
But one of the climate scientists back then said that if they were to burn more wood & poo & cut down the forests the rising CO2 level will change the climate as it would release the carbon into the atmosphere.
(just leave the clam shells at the back of the cave as you leave
