MIRROR NEURONS and imitation learning as the driving force behind the great leap forward in human evolution. By V.S. Ramachandran (2000) 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 Wallaces 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? The solution to many of these riddles comes from an unlikely source.. the study of single neurons in the brains of monkeys. I suggest that the questions become less puzzling when you consider Giaccamo Rizzollatis recent discovery of mirror neurons in the ventral premotor area of monkeys. This cluster of neurons, I argue, holds the key to understanding many enigmatic aspects of human evolution. Rizzollati and Arbib have already pointed out the relevance of their discovery to language evolution . But I believe the significance of their findings for understanding other equally important aspects of human evolution has been largely overlooked. This, in my view, is the most important unreported story in the last decade. THE EMERGENCE OF LANGUAGE Unlike many other human traits such as humor, art, dancing or music the survival value of language is obvious — it helps us communicate our thoughts and intentions. But the question of how such an extraordinary ability might have actually evolved has puzzled biologists, psychologists and philosophers at least since the time of Charles Darwin. The problem is that the human vocal apparatus is vastly more sophisticated than that of any ape but without the correspondingly sophisticated language areas in the brain the vocal equipment alone would be useless. So how did these two mechanisms with so many sophisticated interlocking parts evolve in tandem? Following Darwins lead I suggest that our vocal equipment and our remarkable ability to modulate voice evolved mainly for producing emotional calls and musical sounds during courtship (croonin a toon.). Once that evolved then the brain — especially the left hemisphere — could evolve language. But a bigger puzzle remains. Is language mediated by a sophisticated and highly specialized language organ that is unique to humans and emerged completely out of the blue as suggested by Chomsky? Or was there a more primitive gestural communication system already in place that provided a scaffolding for the emergence of vocal language? Rizzolattis discovery can help us solve this age-old puzzle. He recorded from the ventral premotor area of the frontal lobes of monkeys and found that certain cells will fire when a monkey performs a single, highly specific action with its hand: pulling, pushing, tugging, grasping, picking up and putting a peanut in the mouth etc. different neurons fire in response to different actions. One might be tempted to think that these are motor command neurons, making muscles do certain things; however, the astonishing truth is that any given mirror neuron will also fire when the monkey in question observes another monkey (or even the experimenter) performing the same action, e.g. tasting a peanut! With knowledge of these neurons, you have the basis for understanding a host of very enigmatic aspects of the human mind: mind reading empathy, imitation learning, and even the evolution of language. Anytime you watch someone else doing something (or even starting to do something), the corresponding mirror neuron might fire in your brain, thereby allowing you to read and understand anothers intentions, and thus to develop a sophisticated theory of other minds. (I suggest, also, that a loss of these mirror neurons may explain autism — a cruel disease that afflicts children. Without these neurons the child can no longer understand or empathize with other people emotionally and therefore completely withdraws from the world socially.) edge.org/3rd_culture/ramachandran/ramachandran_p1.html
Posted on: Sun, 28 Sep 2014 05:46:03 +0000
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