WATCH: Making Stone Tools

My name is Nicholas Toth. I am the co-director of the Stone Age Institute and a professor of anthropology at Indiana University. And I want to show you what our ancestors started doing about two and a half million years ago, that we can see on the African continent. The earliest archaeological record are very simple stone tools, and they discovered around this time that if you took two natural cobbles, say from a gravel bar of a river, you could hit one against the other one... and knock off these razor-sharp pieces of stone that archaeologists call flakes. So in a matter of a few seconds, I am producing these very sharp razor blade-like materials... that can be used for, say, cutting up the carcass of an animal that you might kill or maybe you find that's been left by carnivores and a little bit of meat left on the bones that you can cut off. So these are literally razor sharp. If I were to drag this across my finger, I would cut myself quite badly. So, when you think of early stone tools, don't think that they're not razor sharp. They are as sharp as a surgical scalpel. And we can use these for a range of activities as our ancestors did in the early Stone Age, butchering animals, working wood. Say you want to make a spear for hunting or a digging stick for digging up roots and tubers from the branch of a tree. These are great tools for the shaping that you would do for that. And so we see this trajectory in human evolution starting around two and a half million years ago of these very simple types of stone tools. And it is soon after that, by about two million years ago, that we have really good evidence for the expansion of the human brain, for the spread out of Africa shortly after that, the reduction in the size of the teeth and the jaws of our ancestors as well. And starting about one and a half million years ago, they started getting more ambitious and making forms that we call... so-called hand axes. They were probably held in the hand and used as cutting tools. This would be one, it's a more refined one from perhaps about a half a million years ago or so, made out of flint. And so the idea of this is, you would take a larger piece of stone and kind of imagine that form in the middle of it and then again using a hammer slowly but surely, marching around the edges and knocking off flakes. So, I'm using the scar of the flake that was just knocked off as a striking platform to go in the other direction. And the idea is, you want to march all the way around this piece. So, I'm not thinking too much about the final shape yet. I'm just kind of trying to produce an edge... around the circumference of this piece. Okay, and so it would take me about another five minutes to go all the way around this. And then the next stage that our ancestors learned to do... that's called hard-hammer percussion, where you use a hard hammer to knock off flakes. And another thing they learned to do, which is really interesting and somewhat counterintuitive, is you totally steepen the edge, you dull the edge by removing these little flakes with a smaller hammer and then grinding the edge. And then you take a softer material. It could be a piece of hard wood, a fragment of elephant tusk... In this case I'm using an antler of a deer. And you're biting right into the edge... and you're able to remove much longer, thinner flakes when you do that. And this is a way of controlling flaking. I'll do it one more time. And you get a much thinner product at the end of it. And this is called soft-hammer technique. So, I'm going to try to drive a flake off of this side by striking on this side. See how I did that? And by doing that, going around, you can carefully shape the edge, thin it, and make a superb butchery tool. And when people ask, why did they bother to make something this big? They were butchering large animals, sizes of zebra and buffalo on occasion. These are big mammals that weigh hundreds and hundreds of pounds. And would you rather use a razor blade for butchering one of these animals or would you rather use basically a two-fisted tool like this? You have a lot more cutting edge, a lot more weight behind what you're doing as well. And so when we look at the history of technology, you're seeing changes in the refinement of stone tools over time. By the time you get to Neanderthals and early modern humans, they're probably starting to haft tools onto handles, either using some kind of adhesive material like pitch from a pine tree or by using sinew or other material to lash tools together as well. And so we see this progression and refinement of technology through time, especially with stone, but starting around 80,000 years ago. We're also seeing refinement in bone working, that they're starting to make bone tools for the first time as well. And we strongly feel that technology is a very important element in the evolution of the human brain, that without technology we wouldn't have the high quality diet that we need that's driving that brain evolution. Your brain is about three percent of your body weight but about 20% of your energy intake. So it's a very expensive organ to have. So we must have had a very good reason to have a large brain. It probably has to do with becoming very social animals. We're living in larger groups. We have to deal with a number of individuals politically and socially, and so more intelligent animals are able to interact socially in a better way. And so, probably another payoff of these larger brains over time is that we become more inventive and experimental and try new techniques of making and using tools as well. And we become the consummate, the most important dedicated toolmaker in the history of the Earth, as we are today.