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

If I were to give you this story as a script for a science fiction movie, you would probably reject it as too farfetched. It sounds like something straight out of H. G. Welles or Jules Verne. Yet remarkably, it happens to be true. Their discoverers entered them into the scientific record as Homo floresiensis, but many people refer to them by their nickname, hobbits. The bones are only about fifteen thousand years old, which implies that these strange human cousins lived side by side with our ancestors, perhaps as friends, perhaps as foes—we do not know. Nor again do we know why they vanished, although given our species’ dismal record as responsible stewards of nature, it’s a decent bet that we drove them to extinction. But many islands in Indonesia are still unexplored, and it is not inconceivable that an isolated pocket of them has survived somewhere. (One theory holds that the CIA has spotted them already but the information is being withheld until it is ruled out that they are hoarding weapons of mass destruction like blowpipes.)

The hobbits challenge all our preconceived notions about our supposed privileged status as Homo sapiens. If the hobbits had had the resources of the Eurasian continent at their disposal, might they have invented agriculture, civilization, the wheel, writing? Were they self-conscious? Did they have a moral sense? Were they aware of their mortality? Did they sing and dance? Or are these mental functions (and ipso facto, are their corresponding neural circuits) found only in humans? We still know precious little about the hobbits, but their similarities to and differences from humans might help us further understand what makes us different from the great apes and monkeys, and whether there was a quantum leap in our evolution or a gradual change. Indeed, getting ahold of some samples of hobbit DNA would be a discovery of far greater scientific import than any DNA recovery scenario à la Jurassic Park.

This question of our special status, which will reappear many times in this book, has a long and contentious history. It was a major preoccupation of intellectuals in Victorian times. The protagonists were some of the giants of nineteenth-century science, including Thomas Huxley, Richard Owen, and Alfred Russel Wallace. Even though Darwin started it all, he himself shunned controversy. But Huxley, a large man with piercing dark eyes and bushy eyebrows, was renowned for his pugnacity and wit and had no such compunctions. Unlike Darwin, he was outspoken about the implications of evolutionary theory for humans, earning him the epithet “Darwin’s bulldog.”

Huxley’s adversary, Owen, was convinced that humans were unique. The founding father of the science of comparative anatomy, Owen inspired the often-satirized stereotype of a paleontologist who tries to reconstruct an entire animal from a single bone. His brilliance was matched only by his arrogance. “He knows that he is superior to most men,” wrote Huxley, “and does not conceal that he knows.” Unlike Darwin, Owen was more impressed by the differences than by similarities between different animal groups. He was struck by the absence of living intermediate forms between species, of the kind you might expect to find if one species gradually evolved into another. No one saw elephants with one-foot trunks or giraffes with necks half as long their modern counterparts. (The okapi, which have such necks, were discovered much later.) Observations like these, together with his strong religious views, led him to regard Darwin’s ideas as both implausible and heretical. He emphasized the huge gap between the mental abilities of apes and humans and pointed out (mistakenly) that the human brain had a unique anatomical structure called the “hippocampus minor,” which he said was entirely absent in apes.

Huxley challenged this view; his own dissections failed to turn up the hippocampus minor. The two titans clashed over this for decades. The controversy occupied center stage in the Victorian press, creating the kind of media sensation that is reserved these days for the likes of Washington sex scandals. A parody of the hippocampus minor debate, published in Charles Kingsley’s children’s book The Water-Babies, captures the spirit of the times: