The Tell-Tale Brain: A Neuroscientist's Quest for What Makes Us Human

You will see me arguing that many of our unique mental traits seem to have evolved through the novel deployment of brain structures that originally evolved for other reasons. This happens all the time in evolution. Feathers evolved from scales whose original role was insulation rather than flight. The wings of bats and pterodactyls are modifications of forelimbs originally designed for walking. Our lungs developed from the swim bladders of fish which evolved for buoyancy control. The opportunistic, “happenstantial” nature of evolution has been championed by many authors, most notably Stephen Jay Gould in his famous essays on natural history. I argue that the same principle applies with even greater force to the evolution of the human brain. Evolution found ways to radically repurpose many functions of the ape brain to create entirely new functions. Some of them—language comes to mind—are so powerful that I would go so far as to argue they have produced a species that transcends apehood to the same degree by which life transcends mundane chemistry and physics.

And so this book is my modest contribution to the grand attempt to crack the code of the human brain, with its myriad connections and modules that make it infinitely more enigmatic than any Enigma machine. The Introduction offers perspectives and history on the uniqueness of the human mind, and also provides a quick primer on the basic anatomy of the human brain. Drawing on my early experiments with the phantom limbs experienced by many amputees, Chapter 1 highlights the human brain’s amazing capacity for change and reveals how a more expanded form of plasticity may have shaped the course of our evolutionary and cultural development. Chapter 2 explains how the brain processes incoming sensory information, visual information in particular. Even here, my focus is on human uniqueness: Although our brains employ the same basic sensory-processing mechanisms as those of other mammals, we have taken these mechanisms to a new level. Chapter 3 deals with an intriguing phenomenon called synesthesia, a strange blending of the senses that some people experience as a result of unusual brain wiring. Synesthesia opens a window into the genes and brain connectivity that make some people especially creative, and may hold clues about what makes us such a profoundly creative species to begin with.

The next triad of chapters investigates a type of nerve cell that I argue is especially crucial in making us human. Chapter 4 introduces these special cells, called mirror neurons, which lie at the heart of our ability to adopt each other’s point of view and empathize with one another. Human mirror neurons achieve a level of sophistication that far surpasses that of any lower primate, and appear to be the evolutionary key to our attainment of full-fledged culture. Chapter 5 explores how problems with the mirror-neuron system may underlie autism, a developmental disorder characterized by extreme mental aloneness and social detachment. Chapter 6 explores how mirror neurons may have also played a role in humanity’s crowning achievement, language. (More technically, protolanguage, which is language minus syntax.)

Chapters 7 and 8 move on to our species’ unique sensibilities about beauty. I suggest that there are laws of aesthetics that are universal, cutting across cultural and even species boundaries. On the other hand, Art with a capital A is probably unique to humans.

In the final chapter I take a stab at the most challenging problem of all, the nature of self-awareness, which is undoubtedly unique to humans. I don’t pretend to have solved the problem, but I will share the intriguing insights that I have managed to glean over the years based on some truly remarkable syndromes that occupy the twilight zone between psychiatry and neurology, for example, people who leave their bodies temporarily, see God during seizures, or even deny that they exist. How can someone deny his own existence? Doesn’t the denial itself imply existence? Can he ever escape from this Gödelian nightmare? Neuropsychiatry is full of such paradoxes, which cast their spell on me when I wandered the hospital corridors as medical student in my early twenties. I could see that these patients’ troubles, deeply saddening as they were, were also rich troves of insight into the marvelously unique human ability to apprehend one’s own existence.