Search This Blog

Saturday, September 27, 2014


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 "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?
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 Rizzollati's 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 Darwin's 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?
Rizzolatti's 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 another's 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.)

1 comment:

balayogi said...

Evolution and essence of language itself is too comprehensive and too complicated because the term language we use includes too many things, aspects each one of which is being constantly researched and revealed. There seems to be great pearls of logic behind every aspect of every language be it etymology, be it punctuation, be it semantics, be it the syntax , be it the logic for existence of many parts of speech like prepositions in some languages or the lack some parts of speech in some language etc.
Every language has evolved imbued with beauty and utility with marvelous manipulations to make meanings conveyable and meaningful communication.
Language in my opinion has been the most important tool in the growth and development of human evolution in all aspects. However, it still remains a great puzzle with many of its interesting nuances well explained by great scholars, linguists,scientists, attempted to be studied by many psychologists and neurologists but awaiting a very convincing scientific explanation in terms of evolutionary biology or perhaps it could as Dr.V.S. Ramachandran himself says somewhere, "I’m arguing that what happened is more like your jaw bones: there are different adaptations which evolved for different purposes. For example, bones of the ear that evolved for amplifying sound were exapted from reptilian jaw bones used for chewing. There is a fortuitous emergence of different sets of neurosystems that evolved for completely unrelated reasons—and the equally fortuitous interactions between them resulted in early language, which then became an elaborate system. So, it’s not wrong to say that there was natural selection. But there were multiple exaptations with fortuitous interactions which resulted in language.".If existence of biological vocal chord alone were to be credited with the ability to come out with nuanced sound structures to explain and express , then many other species would score over humans. I am on an interesting journey learning about the creation, uses and multiple manifestation of many languages reading the works of many linguists of different languages. The beauty is the very process and purpose of many aspects of any language and absence of certain aspects all reveal great logic and love for human interactions by enhancing human communications