Artist’s conception of Protungulatum
To understand the roots of science, we must look back to the roots of the human species itself. We humans are uniquely endowed with both the capacity and the desire to understand ourselves and our world. That is the greatest of the gifts that set us apart from other animals, and it is why it is we who study mice and guinea pigs and not they who study us. The urge to know, to ponder, and to create, exercised through thousands of millennia, has provided us with the tools to survive, to build for ourselves a unique ecological niche. Using the power of our intellect rather than our physique, we have shaped our environment to our needs, rather than allowing our environment to shape—or defeat—us. Over millions of years, the force and creativity of our minds have triumphed over the obstacles that challenged the strength and agility of our bodies.
When he was young, my son Nicolai used to like to capture small lizards to keep as pets—something you can do when you live in Southern California. We noticed that when we approached the animals, they would first freeze, and then, as we reached down for them, they would flee. We eventually figured out that if we brought along a large box, we could invert it over a lizard before it scurried off, then slide a piece of cardboard under it to complete the capture. Personally, if I’m walking down a dark, deserted street and see anything suspicious going on, I don’t freeze; I immediately cross to the other side. So it’s pretty safe to assume that if I were approached by two giant predators heading toward me, staring eagerly and carrying a gargantuan box, I’d assume the worst and instantly race away. Lizards, though, don’t question their situation. They act purely by instinct. That instinct no doubt served them well over the many millions of years that preceded Nicolai and the box, but it failed them here.
We humans may not be the ultimate in physical specimens, but we do have the ability to supplement instinct with reason and—most important for our purposes—to ask questions about our environment. Those are the prerequisites of scientific thought, and they are crucial characteristics of our species. And so that is where our adventure begins: with the development of the human brain, with its unique gifts.
We call ourselves the “human” species, but the word “human” actually refers not only to us—Homo sapiens sapiens—but to an entire genus called Homo. This genus includes other species such as Homo habilis and Homo erectus, but those relatives are all long gone. In the single-elimination tournament called evolution, all the other human species proved inadequate. Only we, due to the power of our minds, have met all survival challenges (thus far).
Not too long ago, the man who was then the president of Iran was quoted as saying that Jews descended from monkeys and pigs. It is always heartening when a fundamentalist of any religion professes a belief in evolution, so I hesitate to criticize, but actually Jews—and all other humans, too—are descended not from monkeys and pigs, but from apes and rats, or at least ratlike creatures. Called Protungulatum donnae in the scientific literature, our great-great-great-and-so-on-grandmother—the progenitor of our ancestral primates, and of all mammals like us—seems to have been a cute, furry-tailed species whose members weighed in at no more than half a pound.
Artist’s conception of Protungulatum
Scientists believe that these tiny animals first scurried across their habitat around sixty-six million years ago, soon after a six-mile-wide asteroid slammed into the earth. That catastrophic collision threw enough debris into the atmosphere to choke off the sun’s rays for an extended period of time—and generated enough greenhouse gases to send temperatures soaring once the dust had settled. The double whammy of darkness followed by heat killed off about 75 percent of all plant and animal species, but for us it was fortunate: it created an ecological niche in which animals that give birth to live young could survive and thrive without being gobbled up by ravenous dinosaurs and other predators. Over the subsequent tens of millions of years, as species after species emerged and then faded into extinction, one branch of the Protungulatum family tree evolved into our ape and monkey ancestors, and then it branched further, producing our closest living relatives, the chimpanzees and bonobos (pygmy chimpanzees) and, finally, you, the reader of this book, and your fellow humans.
Today most people are comfortable with the fact that Grandma had a tail and ate insects. I go further than mere acceptance: I am excited and fascinated by our ancestry, and the story of our survival and cultural evolution. I think the fact that our ancient grandparents were rats and apes is one of the coolest facts about nature: on our amazing planet, a rat plus sixty-six million years yielded scientists who study the rat, and thus discover their own roots. Along the way, we developed culture and history and religion and science, and we replaced our ancestors’ nests of twigs with gleaming skyscrapers of concrete and steel.
The speed of this intellectual development has been increasing dramatically. Nature required about sixty million years to produce the “ape” from which all humans descended; the rest of our physical evolution occurred in a few million; our cultural evolution has taken only about ten thousand. It is as if, in the words of psychologist Julian Jaynes, “all life evolved to a certain point, and then in ourselves turned at a right angle and simply exploded in a different direction.”
Animal brains first evolved for the most primal of reasons: to better enable motion. The ability to move—to find food and shelter, and to escape from enemies—is of course one of the most fundamental characteristics of animals. Looking backward along the road of evolution to animals such as nematodes, earthworms, and mollusks, we find that the earliest brainlike precursors function to control motion by exciting muscles in the right order. But movement does little good without the ability to perceive the environment, and so even simple animals have a way to sense what is around them—cells that react to certain chemicals, for example, or to photons of light, by sending electrical impulses to the nerves governing motion control. By the time Protungulatum donnae appeared, these chemical- and photosensitive cells had evolved into senses of smell and sight, and the nexus of nerves that controlled muscle movement had become a brain.
No one knows exactly how our ancestors’ brains were organized into functional components, but even in the modern human brain, far more than half the neurons are devoted to motor control and the five senses. That part of our brain that sets us apart from “lower” animals, on the other hand, is relatively small, and was late in coming.
One of the first nearly human creatures roamed the earth just three to four million years ago. It was unknown to us until one blistering day in 1974, when an anthropologist named Donald Johanson, from Berkeley’s Institute of Human Origins, stumbled across a tiny fragment of an arm bone sticking out of the scorched terrain in a parched ravine in remote northern Ethiopia. Johanson and a student soon dug up more bones—thigh and rib bones, vertebrae, even a partial jawbone. All told, they found nearly half the skeleton of a female. She had a woman’s pelvis, a small skull, short legs, and long, dangling arms. Not someone you’d ask to the prom, but this 3.2-million-year-old lady is thought to be a link to our past, a transitional species, and possibly the ancestor from which our entire genus evolved.
Johanson named the new species Australopithecus afarensis, which means “southern ape of Afar,” Afar being the region of Ethiopia in which he made his discovery. He also named the bones: Lucy, after the Beatles song “Lucy in the Sky with Diamonds,” which was playing on the camp radio as Johanson and his team celebrated. Andy Warhol said everyone gets fifteen minutes of fame, and after millions of years, this woman finally got hers. Or to be more accurate, half of her did; her other half was never found.
It is surprising how much anthropologists can discern from half a skeleton. Lucy’s large teeth, with jaws adapted for crushing, suggest that she had a vegetarian diet consisting of tough roots, seeds, and fruit with hard outer coverings. Her skeletal structure indicates that she had a huge belly, which would have been necessary to hold the great length of intestine she’d have needed in order to digest the quantity of vegetable matter she required to survive. Most important, the structure of her spine and knees indicates that she walked more or less upright, and a bone from a member of her species that Johanson and his colleagues discovered nearby in 2011 reveals a humanlike foot, with arches suited to walking, as opposed to gripping branches. Lucy’s species had evolved from a life up in the trees to a life on the ground, enabling its members to forage through the mixed ecology of forest and grassland and to exploit new ground-based food sources such as protein-rich roots and tubers. It was a style of living that many believe spawned the entire Homo genus.
Imagine living in a house and having your mother live next door, her mother next door to her, and so on. Our human heritage is not actually that linear, but, complexities aside, it is interesting to imagine driving along that street, traveling backward in time, and passing generation after generation of ancestors. If you did that, you’d have to drive almost four thousand miles to reach the home of Lucy, who, as a three-foot-seven, sixty-five-pound hairy “woman,” would look more like a chimp to you than a relative. About halfway there, you’d have passed the home of an ancestor who was 100,000 generations removed from Lucy, the first species similar enough to people today—in skeleton and, scientists theorize, in mind—to be classed in the genus Homo. Scientists have dubbed that two-million-year-old species of human Homo habilis, or “Handy Man.”
Homo habilis lived on the immense African savannas at a time when, due to climatic change, the forests were receding. Those grassy plains were not an easy environment, for they served as home to an enormous number of terrifying predators. The less dangerous of the predators competed with Homo habilis for their dinner; the more dangerous tried to make them dinner. One way the Handy Men survived was through their wits—they had a new, larger brain, the size of a small grapefruit. On the fruit-salad scale of brain heft, that is smaller than our cantaloupe but twice the volume of Lucy’s orange.*
When comparing different species, we know from experience that there is usually a rough correlation between intellectual capability and average brain weight relative to body size. Hence, from his brain size we can conclude that Handy Man was an intellectual improvement over Lucy and her kind. Luckily, we can gauge brain size and shape in humans and other primates even if their species is long extinct, because their brains fit snugly into their skulls, which means that if we find a primate skull, we in essence have a cast of the brain that once occupied it.
Lest I appear to be advocating hat size as a proxy for intelligence testing, I should add the disclaimer that when scientists speak of being able to gauge intelligence by comparing brain size, they are talking only about making comparisons between the average brain sizes of different species. Brain size varies considerably among the individuals of a species, but within a species brain size is not directly related to intelligence. For example, modern human brains average about three pounds. Yet the brain of the English poet Lord Byron weighed in at about five pounds, while that of the French writer and Nobel Prize winner Anatole France weighed just a bit more than two, and Einstein’s brain weighed about 2.7. And then there is the case of a man named Daniel Lyons, who died in 1907, at age forty-one. He had normal body weight and normal intelligence, but when his brain was weighed at his autopsy, it was found to tip the scale at a mere 680 grams, about a pound and a half. The moral of the story is that, within a species, the architecture of the brain—the nature of the connections among neurons and groups of neurons—is far more important than the size of the brain.
Lucy’s brain was only slightly larger than that of a chimp. More important, the shape of her skull indicates that the increased brain power was concentrated in regions of the brain that deal with sensory processing, while the frontal, temporal, and parietal lobes—the regions of the brain in which abstract reasoning and language are seated—remained relatively undeveloped. Lucy was a step toward the Homo genus, but not yet there. That changed with Handy Man.
Like Lucy, Handy Man stood upright, freeing his hands to carry things, but unlike Lucy, Handy Man used that freedom to experiment with his environment. And so it happened that roughly two million years ago, a Homo habilis Einstein, or a Madame Curie, or—perhaps more likely—several ancient geniuses working independently of one another, made humankind’s first momentous discovery: if you smash one stone into another at an oblique angle, you can flake off a sharp, knife-edged shard of rock. Learning to bash one rock against another doesn’t sound like the beginning of a social and cultural revolution. Certainly, producing a shard of stone pales in comparison with inventing the lightbulb, the Internet, or chocolate chip cookies. But it was our first baby step toward the realization that we could learn about and transform nature to improve our existence, and that we could rely on our brains to bestow us with powers that complemented and often exceeded those of our bodies.
Homo habilis
To a creature who has never seen a tool of any sort, a kind of jumbo artificial tooth you could grasp in your hand and use for cutting and chopping is a life-changing invention, and it did help to change, completely, the way humans live. Lucy and her kind were vegetarians; microscopic studies of the wear and tear on Homo habilis teeth, and butchering marks on bones found near their skeletons, indicate that the Handy Men had used their stone cutters to add meat to their diet.
Being a vegetarian had exposed Lucy and her species to seasonal shortages of plant food. Having a mixed diet helped Homo habilis bridge those shortages. And because meat is a more concentrated form of nutrients than vegetable matter, meat eaters required a smaller quantity of food than vegetarians. On the other hand, you don’t have to chase down and slaughter a head of broccoli, while procuring animal matter can be quite difficult if you don’t have lethal weapons, which Handy Men lacked. As a result, the Handy Men obtained most of their meat from carcasses left behind by predators like saber-toothed tigers, which, with their powerful front paws and butcher-knife teeth, killed prey that were often far larger than what they could consume themselves. But even scavenging can be difficult if, like the Handy Men, you have to compete with other species. So next time you fret about the half-hour wait for a seat in your favorite restaurant, try to remember that, to obtain their food, your ancestors had to battle wandering packs of fierce hyenas.
In their struggle to procure food, Handy Men’s sharp stones would have made the task of ripping stray flesh off the bone faster and easier, helping to level the playing field with animals who’d been born with the equivalent tools. So once these implements appeared, they became enormously popular, and they remained the human tool of choice for nearly two million years. In fact, it was just such a scattering of stones found alongside fossils of Homo habilis that inspired the name “Handy Man,” bestowed on the species by Louis Leakey and his colleagues in the early 1960s. Since then, the stone choppers have been found to be so abundant at excavation sites that you often have to tread carefully if you don’t want to step on one.
It is a long journey from sharp stones to liver transplants, but, as reflected by his tool use, Homo habilis’s mind had already advanced beyond the capabilities of any of our extant primate relatives. For example, even after years of training by primate researchers, bonobos fail to become proficient in the use of simple stone tools of the type employed by Homo habilis. Recent neuroimaging studies suggest that this ability to design, plan, and use tools arose from the evolutionary development of a specialized “tool use” network in our left brain. Sadly, there are rare cases in which humans with damage to that network do no better than the bonobos: they can identify tools, but, like me before coffee, they cannot figure out how to employ even simple devices such as a toothbrush or comb.
Despite the improved cognitive power, this more-than-two-million-year-old species of human—Homo habilis—is but a shadow of the modern human: still relatively small-brained and also physically small, with long arms and a face only a zookeeper could love. But after its appearance, it didn’t take long—on geological time scales—for several other Homo species to emerge. The most important of those—the one that most experts agree was the direct ancestor of our own species—was Homo erectus, or “Erect Man,” which originated in Africa about 1.8 million years ago. Skeletal remains reveal Erect Man as a species that bore a far greater resemblance to our present-day species than did Handy Man, not just more erect, but bigger and taller—nearly five feet in stature—with long limbs and a much larger skull, which allowed for expansion of the frontal, temporal, and parietal lobes of the brain.
That new larger skull had implications for the birthing process. One thing carmakers don’t have to contend with when redesigning one of their models is how to get the new Hondas to squeeze out the tailpipe of the older Hondas. But nature does have to worry about such things, and so in the case of Homo erectus, the head redesign caused some issues: Homo erectus females had to be larger than their predecessors in order to birth their big-headed, large-brained babies. As a result, while the Homo habilis female was only 60 percent as large as her male counterpart, the average Homo erectus woman weighed 85 percent as much as her mate.
The new brains were worth the cost, for Erect Man marked another abrupt and magnificent shift in human evolution. They saw the world, and approached its challenges, differently than their predecessors had. In particular, they were the first humans to have the imaginative and planning skills to create complex stone and wooden tools—carefully crafted hand axes, knives, and cleavers that required other tools for their construction. Today we credit our brains with giving us the ability to create science and technology, art and literature, but our brain’s ability to conceive of complex tools was far more important to our species—it gave us an edge that aided our very survival.
With their advanced tools, Erect Men could hunt and not just scavenge, increasing the availability of meat in their diet. If the veal recipes in modern cookbooks began by saying, “Hunt down and slaughter a calf,” most people would stick to recipes in books like The Joys of Eggplant. But in the history of human evolution, the new ability to hunt was a giant leap forward, allowing greater consumption of protein and less dependence on the high volumes of plant food previously necessary for survival. Erect Man was probably also the first species to learn that rubbing materials together creates heat, and to discover that heat creates fire. With fire, Erect Man could do what no other animal is capable of: stay warm in climates that would otherwise have been too cold to sustain its life.
I find it somehow comforting that, while I do my hunting at the butcher counter, and my idea of tool use is to call a carpenter, I hail from folks who were quite adept at the practical—even if they did have protruding foreheads and teeth that could gnaw through a yardstick. More important, these new achievements of the mind enabled Homo erectus to branch out from Africa to Europe and Asia, and to persist as a species for well over a million years.
If advances in our intelligence allowed us to make complex hunting and butchering tools, they also created a new, pressing need—for chasing down and cornering a large, fast animal on the savanna is best done by a team of hunters. And so, long before we humans formed all-star basketball and soccer teams, there was evolutionary pressure for our genus to evolve enough social intelligence and planning skill to cohere and band together to score antelopes and gazelles. Erect Man’s new lifestyle therefore favored the survival of those who could best communicate and plan. Here again we see the origins of modern human nature rooted in the African savanna.
Somewhere toward the end of Erect Man’s reign, perhaps half a million years ago, Homo erectus evolved into a new form, Homo sapiens, with even greater cerebral power. Those early, or “archaic,” Homo sapiens were still not beings we would recognize as present-day humans: they had more robust bodies and larger and thicker skulls but brains that were still not quite as large as ours today. Anatomically, modern humans are classified as a subspecies of Homo sapiens that probably didn’t emerge from early Homo sapiens until around 200,000 B.C.
We almost didn’t make it: an amazing recent analysis of DNA by genetic anthropologists indicates that sometime around 140,000 years ago, a catastrophic event—probably related to climate change—decimated the ranks of modern humans, all of whom then lived in Africa. During that period, the entire population of our subspecies plummeted to just several hundred—making us what we would today call an “endangered species,” like the mountain gorilla or the blue whale. Isaac Newton, Albert Einstein, and everyone else you’ve ever heard of, and the billions of us who live in the world today, are all descendants of those mere hundreds who survived.
That close call was perhaps an indication that the new subspecies with the larger brain still wasn’t quite smart enough to make it in the long run. But then we underwent another transformation, one that gave us astonishing new mental powers. It does not seem to have been due to a change in our physical anatomy, not even in the anatomy of our brain. Instead it seems to have been a reworking of how our brain operates. However it happened, it was that metamorphosis that enabled our species to produce scientists, artists, theologians, and, more generally, people who think the way we do.
Anthropologists refer to that final mental transformation as the development of “modern human behavior.” By “modern behavior” they don’t mean shopping or gulping intoxicating beverages while watching sports competitions; they mean the exercise of complex symbolic thought, the kind of mental activity that would eventually lead to our current human culture. There is some controversy about just when that happened, but the most generally accepted date puts the transition at around 40,000 B.C.
Today we call our subspecies Homo sapiens sapiens, or “Wise, Wise Man.” (Your own species ends up with a name like that when you get to choose it yourself.) But all the changes that led to our large brains didn’t come cheap. From the point of view of energy consumption, the modern human brain is the second-most-expensive organ in the body, after the heart.
Rather than endowing us with brains that have such high operating costs, nature could have bestowed upon us more powerful muscles, which, compared with the brain, consume just one-tenth the calories per unit mass. Yet nature chose not to make our species the most physically fit. We humans are not particularly strong, nor are we the most agile. Our nearest relatives, the chimpanzee and the bonobo, savaged their way into their ecological niche through their ability to pull with a force exceeding twelve hundred pounds, and by having teeth so sharp and rugged they tear with ease through hard nutshells. I, on the other hand, have trouble with popcorn.
Rather than impressive muscle mass, humans have oversize craniums, making us inefficient users of food energy—our brains, which account for only about 2 percent of our body weight, consume about 20 percent of our calorie intake. So while other animals are adept at surviving the harshness of the jungle or the savanna, we seem more suited to sitting in a café, sipping mochas. That sitting, though, is not to be underestimated. For as we sit, we think, and we question.
In 1918, German psychologist Wolfgang Köhler published a book, destined to become a classic, called The Mentality of Apes. It was an account of experiments he had conducted on chimpanzees while he was director of a Prussian Academy of Sciences outpost on Tenerife, in the Canary Islands. Köhler was interested in understanding the way chimpanzees solve problems, such as how to procure food that has been placed out of reach, and his experiments reveal much about the mental gifts we share with other primates. But if one contrasts chimpanzee behavior with our own, his book also reveals much about the human talents that help compensate for our physical shortcomings.
One of Köhler’s experiments was especially telling. He nailed a banana to the ceiling and noted that the chimpanzees could learn to stack boxes in order to climb up and get it, but they seemed to have no knowledge of the forces involved. For example, they would sometimes try to stack a box on its edge, or, if stones were placed on the floor so that the boxes toppled over, they would not think to remove the stones.
In an updated version of the experiment, chimps and human children, aged three to five, were taught to stack L-shaped blocks to obtain a reward. Then weighted blocks were surreptitiously substituted for the originals; these toppled over when the chimps and children tried to stack them. The chimps persisted for a while, employing trial and error in failed attempts to earn the reward—but they did not pause to examine the off-balance blocks. The human children also failed the revised task (it wasn’t actually achievable), but they did not simply give up. They examined the blocks in an attempt to determine what the problem was. From an early age, we humans seek answers; we seek a theoretical understanding of our environment; we ask the question “Why?”
Anyone who has experience with young children knows their love of the why question. In the 1920s, psychologist Frank Lorimer made it official: he observed a four-year-old boy over a period of four days and scribbled down all the whys the child asked during that time. There were forty of them, questions such as Why does the watering pot have two handles? Why do we have eyebrows? And my favorite, Why don’t you have a beard, Mother? Human children all around the world ask their first questions at an early age, while they are still babbling and don’t yet speak grammatical language. The act of questioning is so important to our species that we have a universal indicator for it: all languages, whether tonal or nontonal, employ a similar rising intonation for questions. Certain religious traditions see questioning as the highest form of apprehension, and in both science and industry, the ability to ask the right questions is probably the greatest talent one can have. Chimpanzees and bonobos, on the other hand, can learn to use rudimentary signing to communicate with their trainers, and even to answer questions, but they never ask them. They are physically powerful, but they are not thinkers.
If we humans are born with a drive to understand our environment, we also seem to be born with—or at least acquire at a very early age—a gut feeling regarding how the laws of physics operate. We seem to innately understand that all events are caused by other events, and to have a rudimentary intuition for the laws that, after millennia of effort, were eventually uncovered by Isaac Newton.
In the Infant Cognition Laboratory at the University of Illinois, scientists have spent the past thirty years studying the physical intuition of babies by sitting mothers and their children at a small stage or table and observing how the infants react to staged events. The scientific question at hand: With regard to the physical world, what do these infants know, and when did they know it? What they have discovered is that possessing a certain feeling for the workings of physics seems to be an essential aspect of what it means to be human, even in infancy.
In one series of studies, six-month-olds sat in front of a horizontal track that was attached to an inclined ramp. At the bottom of the ramp researchers had placed a toy bug mounted on wheels. At the top of the ramp was a cylinder. Once the cylinder was let loose, the infants watched excitedly as it rolled downward, crashed into the bug, and sent it rolling halfway along the horizontal track for a distance of a couple of feet. Next came the part that excited the researchers: if they reproduced the setup with a different-size cylinder atop the ramp, would the infants predict that, upon collision, the bug would be sent a distance that was proportional to the cylinder’s size?
The first question that came to mind when I heard of this experiment was: How does one know what an infant is predicting? Personally, I have trouble understanding what my kids are thinking, and, being in their teens and twenties, they are all capable of speech. Did I have any insight at all, back when they were limited to smiles, grimaces, and drooling? The truth is, if you hang around babies enough, you do start attributing thoughts to them based on their facial expressions, but it is difficult to confirm scientifically whether your intuition is correct. If you see a baby’s face crinkle up like a prune, is that due to severe gas pains or dismay because the radio just said the stock market tumbled five hundred points? I know my own expression would look the same either way, and with babies, the look is all we have to go by. When it comes to determining what a baby is predicting, though, psychologists have an app for that. They show the baby some chain of events and then measure how long the infant gazes at the scene. If events don’t unfold in the way the baby expected, the baby will stare, and the more surprising the occurrence, the longer the stare.
In the ramp experiment, psychologists arranged for half the infants to watch a second collision in which the rolling cylinder was larger than before, while the others watched a second collision in which the cylinder was smaller. In both cases, however, the tricky researchers had arranged artificially that the bug would be sent rolling farther than in the first collision—all the way, in fact, to the end of the track. The infants who watched the larger cylinder send the bug farther had no exceptional reaction to the events. But sure enough, the infants who saw the bug go farther when struck by a smaller cylinder stared at the bug for a prolonged period, giving the impression that they’d be scratching their heads if only they knew how.
To know that big impacts will send bugs rolling farther than small impacts does not quite make you a peer of Isaac Newton, but, as this experiment illustrates, humans do seem to have a certain built-in understanding of the physical world, a sophisticated intuitive feeling for the environment that complements our built-in curiosity and is far more developed in humans than in other species.
Over millions of years, our species evolved and progressed, gaining a more powerful brain, striving as individuals to learn what we could about the world. The development of the modern human mind was a necessary development if we were to understand nature, but it was not sufficient. And so the next chapter in our story is the tale of how we began to ask questions about our surroundings and to band together intellectually to answer them. It is the tale of the development of human culture.
*For those who prefer precision to fruit, I should add that Handy Man’s brain was half the size of our own.