Capuchin stone tools and the importance of human stone tool shaping
The Archaeology/Anthropology/Palaeoanthropology world is all shook up this week as new research shows a group of wild capuchin monkeys can accidentally make stone flakes. The capuchins hit stones with other stones, licking up the dust. The reason behind this behavior is still a bit unclear, but that's not what everyone is excited about.
In the process of hitting these stones together, capuchin monkeys end up making stone flakes by accident. The repetitive nature of this behavior means that they can make several flakes. The struck stones and the flakes end up looking a bit like some of the tools we find in the archaeological record.
The implication of this finding is that if we accept these accidental capuchin tools look like some archaeological stone tools, we may have to re-think two important points: 1) the makers of the archaeological stone tools need not be human ancestors (hominins) and 2) some archaeological tools could have also been unintentionally made.
The first point is something that the paleoanthropological community has largely understood for quite some time. Knowing what species made which tools is especially difficult as we look deeper back in time. The second point is a tricky one, and that’s where the importance of defining intentional stone tool shaping (my research!) comes in…
Capuchins produce the stone flakes accidentally, in other words, they aren't trying to make tools with specific shapes. The rocks are simply breaking apart according to their physical properties and the forces applied by the capuchins. The goal for these cute critters is making some tasty, salty dust.
Whether or not the tools were made intentionally is a difficult question to ask of hominins who have been long-dead. But stone tools can be made in an ad hoc way and this has relevance to the archaeological record. Even stone tool-making humans today create stone tools with unplanned shapes. Usually this happens when someone needs a sharp cutting edge really quickly. It doesn’t really matter what the tool is shaped like, as long as it has a sharp edge. When you look at the stone from which the flake was struck, it doesn’t look like there was a coherent shaping plan.
Creating multiple tools from a single stone can be more ad hoc or more pre-planned. But making a single tool with a specific shape out of a stone is something different altogether. The goal of this tool-making strategy is to make a single tool, and flakes that get removed along the way are waste. We don't currently have evidence for any non-human species using this type of tool-making strategy.
Humans shape stone tools in intentional ways. The human stone tool record is the most extreme in terms of artifact shape diversity and the maintenance of shaped tool traditions. For example, the “handaxe” is a shaped tool that occurs in archaeological sites for over 1 million years across Africa and Eurasia.
The “handaxe” shape is consistent throughout the archaeological record, and there are specific sets of actions tool-makers use to create these forms.
New phenomena usually don’t occur suddenly in evolution - whether they be new species or new stone tool-making behaviors. We don’t have a solid understanding of how handaxe shaping evolved. The general archaeological consensus assumes that shaping behavior must have started with handaxes because those artifacts look shaped to us (e.g., they are symmetrical, pointed, etc.). While it isn’t that far off-base to believe that a handaxe like this
A handaxe from Italy that is less than 500,000 years old.
was made by a tool-maker with a plan, some of the earliest artifacts that look like handaxes aren’t as convincing...
We need empirically-derived, objective tests to determine whether artifacts were products of flake production (ad hoc) or if they were shaped in a more organized and pre-planned way. The first step is to determine whether the artifacts are measurably different to experimentally-generated stone tools that were created ad hoc (without shaping). If we can show this, then we can explore the possibility that these artifacts were shaped.
My crowdfund project on Experiment will complete the first step in this research – collecting baseline data for stone tools made without shaping.
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