Stone Tools Speak

A common misconception about early humans and their relatives is that they were rough people with primitive tools. Even if our early relatives weren't as technologically advanced as we are, they were by no means primitive.

Yesterday in my class on human origins at the American Museum of Natural History, we studied stone tools, and an archaeologist named Glen came and actually made a stone tool right in front of us during the class. He finds that actually making stone tools helps him in his research because he can understand the process early humans went through to use and make them.

An Acheulean hand-axe from Douro Valley in Zamora, Spain.
Art by Josè-Manuel Benito Álvarez.

The process of making stone tools is known as flint knapping. To make a tool, like let's say a battle axe, flint knappers tap their blank (the stone that will eventually become the tool) with a billet (a tool used for striking the blanks). Blanks are made of stones like flint, obsidian, and chert because these stones are made out of the same material throughout so they break predictably. These stones are also hard, and they make good sharp tools. Billets, on the other hand, are made of softer material, like copper or antler.

Tapping the blank with a billet creates pressure waves in the rock which cause it to break into neat shards. When a shard breaks off, it has wave-like ridges on it. These ridges have the shape of the pressure wave that broke the rock. A pressure wave takes about a millisecond to break a blank, but the pressure wave marks stick around for thousands of years.  I think it's cool how a rock shard from thousands of years ago can document one millisecond of history.

Stone tools require skill to make and are extremely sharp. A fresh shard of rock is sharper than steel can ever be, but it dulls faster. This problem can be fixed easily by tapping off a fresh edge for the stone, or by just making a new tool. We got to test out the sharpness of leftover shards from the spearhead Glen made on apples, carrots and bananas, and they cut almost as well as any knife.

Tools made using the Levallois technique.
 Specimen from La Parrilla, in Valladolid, Spain.
 Art by Josè-Manuel Benito Álvarez.

Stone tools were not only useful for prehistoric humans, they help archaeologists today study and understand the past. Stone tools are great additions to the fossil record because, being stone, they preserve well and they can tell researchers many things, from what early humans were hunting to how advanced their language development was.

At first I was confused as to how stone tools could give us any information about language development, but now that I think about it, it makes sense. Complex tool stone tools were difficult enough to make that it would have taken pretty advanced communication skills to teach anyone how to make them. Also, as time passed, tools like spears became more popular than the good-old hand axe.  Spears, however, couldn't kill an animal with one blow. To use the spears effectively, early humans would have had to work in a group with an advanced plan of attack. Plans require good communication abilities.

It ends up that "primitive" stone tools are actually markers of an advanced society with a spoken language.