Abstract

Modern human beings are most sharply distinguished from all other organisms alive today by their possession of symbolic reasoning, the cognitive capacity that makes possible the mental construction of alternative versions of the world. Scrutiny of the human fossil and archaeological records reveals that, while brain sizes expanded independently in several hominid lineages over the course of the Pleistocene, this qualitatively distinctive symbolic faculty only emerged in our own. What is more, this acquisition was made remarkably recently: well within the 200,000-year tenure on Earth of our anatomically distinctive species Homo sapiens. The earliest anatomical Homo sapiens appear to have behaved in much the same manner as their non-symbolic contemporaries, although it is highly likely that they had acquired the neural wiring necessary for symbolic thought in the same event of developmental reorganization that gave Homo sapiens its strikingly derived bony morphology. Only subsequent to about 100,000 years ago do archaeological traces suggest that our forebears had actually begun to think symbolically. This implies that the new capacity was released by a purely cultural stimulus. I suggest that cultural trigger involved was the spontaneous invention of language by members of a small population isolate of Homo sapiens in Africa, at some time after about 100,000 years ago. Structured, rule-bound language is intricately intertwined with symbolic thought as we experience it today; and it is possible to conceive at least in principle how each could have fed back into the other to create a new dynamic.