Notes on ACAAPNZ 2008 II

A third selection from the 2008 annual conference of the NZ division of the Australasian Association of Philosophy

Tool Use and Life History of Early Homos. Ben Jeffares (ANU).

How to account for human cognitive and social evolution? One approach is to focus on the physical evidence of human evolution (skeletons, tools, drawings, etc.) and on the periods where this physical evidence indicates dramatic changes in human life, thought and behavior. This is Jeffares' approach, and in this talk he concentrated on a dramatic change in human tool use that seems to have taken place around 1.5 million years ago.

1.5mya is a hotspot for archaeologists because it's meant to be the great coming of age of our species – the point where we stopped being walking chimps and became hairy humans. And a jump in tool use is the main marker of this shift. Jeffares thinks tools were around well before the point where the first appear in the archaological record. Skeletal remains indicate that early bipeds had a hand structure suitable for tool-use well before 2.5mya. Be that as it may, tools became more refined around 1.5mya, being more symmetrical and sophisticated and more likely to be “time travellers”: made in advance and for repeated use.

How to account for this change? It's really quite interesting, but the evidence is fragmentary. Studies have suggested that homos started living differently around the time that tool-makers sharpened their act. The started having longer childhoods, longer periods of learning and maturing: the age of the teenager had begun. They also had patchier resources, had to kill away from home and in unknown places. So they had to plan ahead, making tools at home using secure resources. And, crucially, the children sat around while the tool-makers worked, and the tools lay around as well. Teaching ensured that any new skills or gizmos could be passed on. And the tools that lay around acted as “templates”, finished products that young killers could copy. As Jeffares put it, students could learn from “products”, not just from “behaviors.”

A nice story, but is it true? Jeffares is sensitive to the weaknesses of the evidence, and with good reason. It is not an exaggeraion to say that the extended-childhood data is based often based on “half a dozen teeth.” Human evolution is light on evidence and heavy on theorising – not necessarily a bad thing, and good for philosophers. There's some doubt about Jeffares' early tool-use thesis. Tools are not the only reason that manual dexteritry, of the kind found in skeletal remains, can arise. As Sterelny puts it, “it's always important to be able to scratch your bum.” Turning over rocks for food, extracting berries or flesh, forcing other animals to the ground: all would need precise and powerful grips.

Some will also question the inference from stone-crafting to tool-use. Some of the stones in question are beautifully symmetric, crafted beyond the needs of mere huntsmen. They have the look of ornaments, icons. Jeffares insists, though, that the elegant tear-drop stones are the exception. And there's no need to worry about the fact they have a sharp edge all the way round. True, this would make them inpracticable as hammers or weapons. But they were not always like that, says Jeffares. Whenever one edge wore out, our frugal ancestors worked on another edge of the same stone -- and so on until the stone was crafted all the way around. It's only the finished product we see.