Dictionary of Human Evolution and Biology

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Tool-feedback Hypothesis

Proposal by Charles Darwin in The Descent of Man which stated that small canines, bipedalism, and large brain size in hominids evolved together in a positive feedback mechanism in which tool use was the primary catalyst. According to this scenario, as proto-hominids began to use tools they had to stand upright when carrying the tools; canine teeth, previously large and used as tools, were reduced owing to disuse; the brain enlarged because tool use required elaborate hand-eye coordination. When Darwin proposed this hypothesis there was very little supportive evidence from the fossil record. When hominid fossils became more extensive in the twentieth century, the tool-feedback hypothesis was rejected, as the new fossils indicated that bipedalism preceded increased brain size.

Cf. Washburn’s biocultural feedback model.

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