GS- have you ever lived in a colder climate? you can burn a lot of calories just by staying warm. also the type of physical labor these men were doing is reason alone they ate so much. they had to chop and haul their own wood and water, hunt and trap, take care of horses, they probably were on their feet moving around and carrying weight all day and possibly nomadic. 6 pounds of lean game meat might only be 5000 calories, if you ate that every day or every other its really not so much. its much easier to let the forest and wild lands grow that much food in animal then to destroy these lands that feed the wildlife to grow starch.