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MIRROR NEURONS and imitation learning as the driving force behind "the great leap forward" in human evolution

By V.S. Ramachandran

The discovery of mirror neurons in the frontal lobes of monkeys, and their potential relevance to human brain evolution — which I speculate on in this essay — is the single most important "unreported" (or at least, unpublicized) story of the decade. I predict that mirror neurons will do for psychology what DNA did for biology: they will provide a unifying framework and help explain a host of mental abilities that have hitherto remained mysterious and inaccessible to experiments.

There are many puzzling questions about the evolution of the human mind and brain:

1) The hominid brain reached almost its present size — and perhaps even its present intellectual capacity about 250,000 years ago . Yet many of the attributes we regard as uniquely human appeared only much later. Why? What was the brain doing during the long "incubation "period? Why did it have all this latent potential for tool use, fire, art music and perhaps even language- that blossomed only considerably later? How did these latent abilities emerge, given that natural selection can only select expressed abilities, not latent ones? I shall call this "Wallace's problem", after the Victorian naturalist Alfred Russell Wallace who first proposed it.

2) Crude "Oldawan" tools — made by just a few blows to a core stone to create an irregular edge — emerged 2.4 million ago and were probably made by Homo Habilis whose brain size was half way (700cc) between modern humans (1300) and chimps (400). After another million years of evolutionary stasis aesthetically pleasing "symmetrical" tools began to appear associated with a standardization of production technique and artifact form. These required switching from a hard hammer to a soft (wooden?) hammer while the tool was being made, in order to ensure a smooth rather than jagged, irregular edge. And lastly, the invention of stereotyped "assembly line" tools (sophisticated symmetrical bifacial tools) that were hafted to a handle, took place only 200,000 years ago. Why was the evolution of the human mind "punctuated" by these relatively sudden upheavals of technological change?

3) Why the sudden explosion (often called the "great leap" ) in technological sophistication, widespread cave art, clothes, stereotyped dwellings, etc. around 40 thousand years ago, even though the brain had achieved its present "modern" size almost a million years earlier?

4) Did language appear completely out of the blue as suggested by Chomsky? Or did it evolve from a more primitive gestural language that was already in place?

5) Humans are often called the "Machiavellian Primate" referring to our ability to "read minds" in order to predict other peoples' behavior and outsmart them. Why are apes and humans so good at reading other individuals' intentions? Do higher primates have a specialized brain center or module for generating a "theory of other minds" as proposed by Nick Humphrey and Simon Baron-Cohen? If so, where is this circuit and how and when did it evolve?