For many decades It was assumed that the human brain must be special, as superior to the brains of other mammals as our minds are. This specialness was never seriously questioned, and even basic facts, like asserting that the human brain contains 100 billion neurons, were arrived at with surprising casualness.
In an interesting 2013 TED talk, the articulate Brazilian neuroscientist Suzana Herculano-Houzel offers clarity for the first time on several of the basic issues. After devising a way to dissolve brain cell membranes so that only the nuclei remained, and isolating them to be counted, she determined that the human brain contains 86 billion neurons, the most of any primate. Even though the human brain is a small fraction of our total weight, it uses 25% of a person’s daily calorie consumption.
That may seem like an incidental fact, but Herculano-Houzel makes it the cornerstone of her argument, which declares that the human brain isn’t special. We have primate brains, she says, that are in proportion to our primate relatives like chimpanzees and gorillas. But in an odd evolutionary twist, chimps and gorillas cannot sustain the calorie load of an immense brain by eating raw food. Typically, a great ape feeds for eight hours a day to sustain its large body, and over time a choice was made to prefer a very large body with a smaller number of neurons.
In Homo sapiens the reverse occurred. We chose a small body and a huge brain, particularly the higher brain responsible for our superior mind. According to Herculano-Houzel’s explanation, this choice was made possible by the invention of cooking. Cooking raw food is like pre-digesting it outside the body; cooked food is easier to digest, contains more nutrients by weight than raw food, and takes many fewer hours to eat. You can get an entire day’s calorie load with a 15-minute visit to a fast-food chain.
So there you have it: cooking led to the enormous number of neurons we possess, and they in turn allowed our huge cognitive capacity to evolve in a growth spurt that took the early hominid brain on a skyrocketing curve for the last 1.5 million years since the discovery of fire.
But as intriguing as this hypothesis is, and as essential as fire was to human evolution, the whole thing doesn’t hold water. To begin with, if we started out in our hominid ancestry with unevolved primate brains, how were such brains smart enough to discover fire? No other higher primate did, and they already possessed big brains on the mammalian ladder. Second, how does counting neurons have anything to do with the mental abilities that created civilization? Plenty of people possess the full complement of 86 billion neurons but who lead totally ordinary lives.
It does not occur to them to exploit our almost infinite capacity for creativity. They just live their lives by working and raising families. Primitive cultures faced enormous challenges simply to do the same, leaving almost no time for art, music, invention, discovery, philosophy, religion, and the other accoutrements of civilization. Why and how could a clump of brain cells, even a huge clump, decide to follow such a trajectory?
The earliest representations of a human figure in sculptural form date back not to early Homo sapiens but to Homo erectus, somewhere between 250,000 and 750,000 years ago. There is evidence that Neanderthals buried their dead in cave tombs, wore decorative jewelry, and perhaps performed religious ceremonies. If you stop to think about it, there was no pressing reason for the brain to need the wheel or pottery—Australian aborigines existed between 45,000 and 60,000 years, the longest continuous indigenous culture on earth, without either.
The problem with basing human achievements on our big brains is that at bottom, neuroscience assumes that we are brain puppets. It sounds almost ridiculously simple, but that’s like saying that without a radio you cannot explain music. Putting the apparatus first is such an obvious mistake, you wouldn’t think a science as advanced as brain science would make it—but it has. The equation of Brain = Mind puts the apparatus first. Either the brain created the mind or they developed in some mysterious relationship.
Since science is about clearing up mysteries, the inability to decide how brain relates to mind has been too frustrating. As a short cut, why not say that the brain created the mind? It cut through all the philosophical red tape. Yet for all the convenience that it brings to brain research, there is zero proof that the brain creates the mind. At no point can anyone show how cells that are constituted from the same DNA as heart, liver, and lung cells somehow learned to think. The very notion that the brain thinks is empty; it is like saying that a piano understands Mozart.
We will never get the brain right until we follow the second path and delve into the mystery of how the mind and brain relate to each other. It is false to assume that brain experts are also mind experts; they aren’t. By adopting the false assumption that the brain is the mind, for all practical purposes, neuroscience has left out the true nature of intelligence, creativity, love, art, compassion, spiritual experiences, and higher evolution. Those things belong to the evolution of the human mind and remain completely baffling if you only stare at neurons through a microscope.
Realizing this, there is a movement to confront the real mystery, which is consciousness itself. Consciousness cannot be shown to be a created thing. The brain is a created thing—we can follow its physical evolution with considerable accuracy now. But at no point does consciousness appear out of the physical “stuff” of creation. It may be, as some theorists argue, that consciousness is innate in creation. It has always been there. The irony is that once we pay serious attention to consciousness, which will unravel the mystery of being human, it will be consciousness that explains consciousness to itself.
Reprinted from San Francisco Chronicle with permission
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