Two important issues. First, the average of 3300 calories a day doesn't mean you have to come up with 3300 calories a day. Traditional hunter-gatherers lived much more in a boom and bust society than we are used to. Finding a large food supply and consuming 9000 calories a day for 3 days, then having a week of 1000 calorie-days worked then and is probably more likely. Second, the ability to live off the land is very dependent on the land where you are. I'm in southern Louisiana where it is relatively easy to go out and get dinner out of the ditch alongside of the road. So where you are along with an understanding of the land itself makes a big difference. In my younger days on the farm I knew where to find fish and turtles, where to get a deer or assorted small game, where the wild fruits and grains were, and so on. So a little knowledge can go a long way, and not just a general knowledge of "here is how you do" but a more specific "here is how you do it HERE."