The Meaning of Human Existence (12 page)

I once kept anole lizards from different West Indian islands in my laboratory, in order to study their territorial displays. The thumb-sized reptiles are everywhere abundant on trees and shrubs, where they prey on insects, spiders, and other small invertebrate animals. An adult male threatens rivals by lowering a flap of skin beneath his neck called the dewlap. The dewlap of each species has a different color, usually a shade of red or yellow or white; and males of the same species respond solely to that color. I found I needed only one male, not two, to get a territorial dewlap display. All I had to do was hold a mirror against the side of the terrarium. The resident male then displayed to his own image (resulting in a draw every time).

Infant sea turtles hatch from eggs buried in the sand of a beach by their mothers, who emerge from the sea solely for this purpose. Each of the hatchlings digs itself out and immediately crawls down to the sea, where it will spend the rest of its life. What attracts the newborn little animal is not, however, the many distinctive sights and odors emanating from the water’s edge. The lure is instead the brighter light reflected off the surface of the water. When experimenters turned on an even brighter
light close by, the baby turtle followed it, even when the light led it directly away from the sea.

Humans and other large-brained mammals are also guided by inherited key stimuli and instincts, but they are not nearly so rigid or simpleminded as those of lower animals. Instead, people in particular are ruled by what psychologists call prepared learning. What is inherited is the likelihood of learning one or a few alternative behaviors out of many possible. The strongest among the biased behaviors are shared across all cultures, even when they seem irrational and there are plenty of opportunities to make other choices.

I am a mild arachnophobe. I’ve tried on occasion but cannot bring myself to touch a large spider hanging in its web, even though I know it won’t bite me, and even if it did, the bite would not be venomous. I’ve harbored this groundless fear ever since, at the age of eight, I was frightened by the sudden jerking behavior of a big garden spider of the orb-weaving genus
Araneus
. I had approached to examine the monster (so it seemed to me) closely, as it hung in sinister quietude in the center of its web, and was startled by its sudden response. Today I know its scientific name and a lot about its biology—as I should, having served for years as a curator of entomology at Harvard University’s Museum of Comparative
Zoology. But I still won’t—can’t—touch large spiders hanging in their webs.

This kind of revulsion sometimes deepens in people to a full-blown phobia, characterized by panic, nausea, and an inability even to think rationally about the object of fear. Since I’ve just confessed a moderate, unjustified aversion, I’ll also admit to the only true phobia I possess. I cannot bear nor will I tolerate under any imaginable condition having my arms pinned forcibly and my face covered. I remember with certainty the moment this response began. When eight years old, the year of the spider, I had a frightening eye operation. I was anesthetized in the nineteenth century manner—laid supine on an operating table without explanation or any I can recall, my arms then held down and a piece of cloth placed over my face into which ether was dripped. I was screaming as I struggled. Something deep within me must have said, Never again! To this day I have a “testing” fantasy of the phobia. I am held at gunpoint by an imaginary robber who tells me that he intends to tie my arms and place a hood over my face. My response in this scenario, and I believe it would be in reality as well, is to say, “No, you’re not. So go ahead, shoot me.” I would rather die than be tied up and hooded.

Phobias take a long time and a lot of therapy to remove. Yet they can be acquired with only a single experience,
as I and so many others have personally discovered. The sudden appearance of something writhing on the ground, to take a second example, is enough for some people to acquire a phobia against snakes.

How could such overkill in learning confer any advantage? The clue is in the objects of the phobias themselves, which comprise mostly spiders, snakes, wolves, running water, closed spaces, and crowds of strangers. These were among the ancient perils of the prehumans and early human hunter-gatherers across millions of years. Our distant ancestors regularly faced injury or death while hunting for food too close to the edge of a ravine, or when they stepped carelessly on a venomous snake, or stumbled upon a raiding party of an enemy tribe. It was safest to learn fast, remember the event long and vividly, and act decisively without involving rational thought.

In contrast, automobiles, knives, guns, and the excessive consumption of dietary salt and sugar are among the leading causes of present-day mortality. Yet no inborn propensities to avoid them have evolved. The likely reason is the lack of time for evolution to have hardwired them into our brains.

Phobias are an extreme, but all behaviors acquired by prepared learning, having provided adaptive value during the ancestry of the human species, are part of human instinct. Yet most are also transmitted by culture
from one generation to the next. All human social behavior is based on prepared learning, but the intensity of the bias varies from one case to another as a product of evolution by natural selection. For example, human beings are born gossips. We love the life stories of other people, and cannot be sated with too much such detail. Gossip is the means by which we learn and shape our social network. We devour novels and drama. But we have little or no interest in the life stories of animals—unless they are linked in some way to human stories. Dogs love others and yearn to return home, owls ponder, snakes sneak, and eagles thrill at the freedom of the open sky.

Human beings were made for music. Its thrill and rapture are picked up almost immediately by little children. However, the thrill (and scarcely ever rapture) of analytic mathematics comes a great deal more slowly and much later, if ever. Music served early humanity as a means of integrating societies and heightening the emotions of the people, but analytic mathematics never did. Early humans had the mental capacity to elaborate analytic mathematics, but not to love it. Only evolution by natural selection can create the need for bedrock instinctual love.

The driving force of natural selection has directed the convergence of cultural evolution among societies
around the world. A classic synthesis of cultures made from the Human Relation Area Files in 1945 listed sixty-seven universals, including the following (selected here at random): athletic sports, bodily adornment, decorative art, etiquette, family feasting, folklore, funeral rites, hairstyles, incest taboos, inheritance rules, joking, and the propitiation to supernatural beings.

What we call human nature is the whole of our emotions and the preparedness in learning over which those emotions preside. Some writers have tried to deconstruct human nature into nonexistence. But it is real, tangible, and a process that exists in the structures of the brain. Decades of research have discovered that human nature is not the genes that prescribe the emotions and learning preparedness. It is not the cultural universals, which are its ultimate product. Human nature is the ensemble of hereditary regularities in mental development that bias cultural evolution in one direction as opposed to others and thus connect genes to culture in the brain of every person.

Among the more consequential hereditary biases in learning is the selection of the habitat in which people prefer to live. Adults are drawn to the kinds of environments in which they grew up and were shaped by their most formative experiences. For them, mountains, seashores, plains, and even deserts variously provide the
habitats that give the greatest sense of familiarity and comfort. Having been raised myself mostly close to the Gulf of Mexico, I like best a flat, low plain that slopes down to the sea.

However, on a smaller scale within these panoramas, and for children not yet fully acculturated, laboratory experiments have yielded a different story. Volunteers from several countries with very different cultures were asked to evaluate photographs of a wide range of habitats where in fantasy they might live. The choices varied from dense forests to deserts, and other ecosystems in between. The preferred choice had three factors: the ideal vantage point is on a rise looking down, a vista of parkland comprising grassland sprinkled with trees and copses, and proximity to a body of water, whether stream, pond, lake, or ocean.

This archetype happens to be close to the actual savannas of Africa where our prehuman and early ancestors evolved over millions of years. Is it possible that the preference for the environment of the species remains as a residue of prepared learning? The “African savanna hypothesis,” as it is called, is not at all a conjecture out of the blue. All mobile animal species, from the tiniest insects to elephants and lions, instinctively choose the habitats to which all the rest of their biology is best adapted. If they did not, they would be
less likely to find a mate, the food on which they are dependent, or the means to avoid unfamiliar parasites and predators.

At the present time rural human populations around the world are imploding into cities. With any luck, their lives are improved by the better access to markets, schools, and medical centers. They also have a greater opportunity to support themselves and their families. But given a free choice, all else being equal, do they really prefer cities and suburbs as habitats? Because of the intense dynamism of urban ecology and the artifactual environment forced on them, it is impossible to say. So, to learn what people actually prefer and acquire when given a completely free choice, it is better to turn to those with a great deal of money. As landscape architects and high-end real estate agents will tell you, the rich prefer habitations set on a rise that looks out over parkland next to a body of water. None of these qualities have practical value, but people with sufficient means will pay any price to have them.

A few years ago I had dinner at the home of a distinguished and wealthy friend, who happened to be a firm believer in the brain as a blank slate, unencumbered by instinct. His home was a penthouse overlooking New York’s Central Park. As we walked out onto the terrace, I noticed that its outer edge was lined with small potted
trees. We looked down from there onto the distant grassy center of the park and one of its two artificial lakes. We agreed that the vista was all quite beautiful. Being a guest, I refrained from asking him the burning question: Why is it beautiful?

13

Religion

R
apture, a “joy excessive and sweet,” as Spain’s great mystic Saint Teresa of Ávila described it in her 1563–65 diary, can be achieved variously by music, religion—and hallucinogenic drugs such as the Amazonian religion-enhancer ayahuasca. Neurobiologists have tracked at least some of the peak experience of music to at least one cause, the release of the transmitter molecule dopamine within the striatum of the brain. The same biochemical reward system also mediates pleasure in food and sex. Because music began in Paleolithic times—bird-bone and ivory flutes date back more than thirty thousand years—and because it remains universal in hunter-gatherer societies around the world, it is reasonable to conclude that our loving devotion to it has been hardwired by evolution in the human brain.

In almost all living societies, from hunter-gatherer to civilized-urban, there exists an intimate relation
between music and religion. Are there genes for religiosity that prescribe a neural and biochemical mediation similar to that of music? Yes, says evidence from the relatively young discipline of the neuroscience of religion. The methods of inquiry include twin studies that measure the role of genetic variation, along with studies of hallucinogenic drugs that mimic religious experience. Also used are data concerning the impact on religiosity of brain lesions and other disorders, and, not least, the direct trajectory of the neural events tracked by brain imaging. Altogether, the results of the neuroscience of religion thus far suggest strongly that a religious instinct does indeed exist.

Of course there is far more to religion than its biological roots. Its history is as old or nearly so as that of humanity itself. The attempted resolution of its mysteries lies at the heart of philosophy. The purest, most general form of religion is expressed by theology, of which the central questions are the existence of God and God’s personal relation to humanity. Deeply religious people want to find a way to approach and touch this deity—if not His literal transubstantiated flesh and blood in the Catholic manner, at least to ask Him for personal guidance and beneficence. Most also hope for life after death, passing into an astral world where they will join in bliss those who have gone before. Theological spirituality, in
short, seeks the bridge between the real and the supernatural. It dreams of God’s dominion, where souls of the Earthly dead live on together in peaceful eternity.

The brain was made for religion and religion for the human brain. In every second of the believer’s conscious life religious belief plays multiple, mostly nurturing roles. All the followers are unified into a vastly extended family, a metaphorical band of brothers and sisters, reliable, obedient to one supreme law, and guaranteed immortality as the benefit of membership.

The deity is higher than any prophet, high priest, imam, mystic saint, cult leader, president, emperor, dictator, the lot. He is the final and forever alpha male, or She the alpha female. Being supernatural and infinitely powerful, the deity can perform miracles beyond the reach of human understanding. Throughout prehistory and most of history, people needed religion to explain the occurrence of most phenomena around them. Torrential rain and flooding, a lightning bolt streaking across the sky, the sudden death of a child. God caused it. He or She was the cause in the cause-and-effect required for sanity. And the ways of God, albeit charged with meaning for our lives, are a mystery. With the coming of science, more and more natural phenomena have come to be understood as effects linked to other analyzable phenomena, and supernatural explanations of cause-and-effect
have receded. But the deep, instinctive appeal of religion and religionlike ideology has remained.