And that is what we estimate the world population was at around the time of the last ice age, or shortly afterwards. And that's because a tribe of 100 hunter-gatherers is going to need 50 square kilometers to 100 square kilometers to hunt and gather from, or actually 500 were some of the estimates I've seen. And it might seem like a lot of area that you would need to hunt and gather from, but imagine if you and your family had to go live in the woods now. How much food could you actually find? You would have to walk miles and miles per day if you're trying to hunt. You would have to walk miles and miles per day to get whatever wild grains or berries or whatever, or mushrooms or whatever, or insects that you might consume. But then with the advent of agriculture, it allowed for a much, much higher density population.