The Old Stone Age is the great bulk of human history. And there's also a Mesolithic that comes about 15, 20,000 years ago. But then around 10,000 years ago, the stones have a much more polished appearance to them, things like this. And so that period from about 10,000 years, starting with about 10, 15,000 years ago, depending on what part of the world you look at, is referred to as the Neolithic period. Neolithic, referring to new stone. And on top of this timeline, I have also shown what's happening at a very large scale climactically on the Earth. So these blue periods are Ice Ages, and these reddish-orange periods are the periods in between Ice Ages.