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Chapter 28
TWENTY YEARS EARLIER, in a tiny basement lab, a young scientist stared into a corpse andsaw his destiny staring back.

At that moment, David Carrier was an undergraduate at the University of Utah. He was puzzlingover a rabbit carcass, trying to figure out what the deal was with those bony things right over thebutt. The bony things bugged him, because they weren’t supposed to be there. David was the starstudent in Professor Dennis Bramble’s evolutionary biology class, and he knew exactly what hewas supposed to see whenever he cut into a mammal’s abdomen. Those big belly muscles on thediaphragm? They need to anchor down on something strong, so they connect to the lumbarvertebra, just the way you’d lash a sail down to a boom. That’s how it is for every mammal from awhale to a wombat—but not, apparently, for this rabbit; instead of grabbing hold of somethingsturdy, its belly muscles were connected to these flimsy chicken-wing-looking things.

David pushed one with his finger. Cool; it compressed like a Slinky, then sprang back out. Butwhy, in all mammaldom, would a jackrabbit need a spring-loaded belly?

“That made me start thinking about what they do when they run, the way they arch their backswith every galloping stride,” Carrier later told me. “When they push off with their hind legs, theyextend the back, and as soon as they land on the front legs, the back bends dorsally.” Lots ofmammals jackknife their bodies the same way, he mused. Even whales and dolphins move theirtails up and down, while a shark slashes from side to side. “Think of an inchworming cheetahmovement,” David says. “Classic example.”

Good; this was good. David was getting somewhere. Big cats and little rabbits run the same way,but one has Slinkies stuck to its diaphragm and one doesn’t. One is fast, but the other has to befaster, at least for a little while. And why? Simple economics: if mountain lions ran down all therabbits, you’d have no more rabbits and, eventually, no more mountain lions. But jackrabbits areborn with a big problem: unlike other running animals, they don’t have reserve artillery. Theydon’t have antlers or horns or hard-kicking hooves, and they don’t travel in the protection of herds.

For rabbits, it’s all or nothing; either they dart their way to safety, or they’re cat food.

Okay, David thought, maybe the Slinkies have something to do with speed. So what makes youfast? David began ticking off components. Let’s see. You need an aerodynamic body. Awesomereflexes. Power-loaded haunches. High-volume capillaries. Fast-twitch muscle fiber. Small, nimblefeet. Rubbery tendons that return elastic energy. Skinny muscles near the paws, beefy muscles nearthe joints …Damn. It didn’t take David long to figure out he was heading toward a dead end. A lot of factorscontribute to speed, and jackrabbits share most of them with their hunters. Instead of finding outhow they were different, he was finding out how they were alike. So he tried a trick Dr. Bramblehad taught him: when you can’t answer the question, flip it over. Forget what makes something gofast— what makes it slow down? After all, it didn’t just matter how fast a rabbit could go, but howfast it could keep going until it found a hole to dive down.

Now that one was easy: other than a lasso around the leg, the quickest way to bring a fast-movingmammal to a halt is by cutting off its wind. No more air equals no more speed; try sprinting whileholding your breath sometime and see how far you get. Your muscles needs oxygen to burncalories and convert them into energy, so the better you are at exchanging gases—sucking inoxygen, blowing out carbon dioxide—the longer you can sustain your top speed. That’s why Tourde France cyclists keep getting caught with other people’s blood in their veins; those illicittransfusions pack in extra red-blood cells, which carry lots of extra oxygen to their muscles.

Wait a second … that meant that for a jackrabbit to stay one hop ahead of those snapping jaws, itwould need a little more air than the big mammal on its tail. David had a vision of a Victorianflying machine, one of those wacky but plausible contraptions rigged with pistons and steamvalves and endless mazes of wheezing levers. Levers! Those Slinkies were beginning to makesense. They had to be levers that turbocharged the rabbit’s lungs, pumping them in and out like afireplace bellows.

David ran the numbers to see if his theory held up and … bingo! There it was, as elegant andniftily balanced as an Aesop’s fable: Jackrabbits can hit forty-five miles per hour, but due to theextra energy needed to operate the levers (among other things), they can only sustain it for a halfmile. Cougars, coyotes, and foxes, on the other hand, can go a lot farther but top out at forty milesper. The Slinkies balance the game, giving the otherwise defenseless jackrabbits exactly forty-fiveseconds to either live or die. Seek shelter quickly and live long, young Thumper; or get cockyabout your speed and be dead in less than a minute.

“You know,” he thought, “if you take away the levers, isn’t it the same engineering for every othermammal?” Maybe that’s why their diaphragms hooked on to the lumbar vertebra—not because thevertebra was sturdy and wouldn’t move, but because it was stretchy and would. Because it flexed!

“It seemed obvious that when the animal pushed off and extended its back, it wasn’t just forpropulsion—it was also for respiration,” David says. He imagined an antelope racing for its lifeacross a dusty savannah, and behind it, a streaking blur. He focused on the blur, froze it in place,then clicked it forward a frame at a time:

Click—as the cheetah stretches long for a stride, its rib cage is pulled back, sucking air into thelungs and …Click—now the front legs whip back until front and rear paws are touching. The cheetah’s spinebends, squeezing the chest cavity and squishing the lungs empty of air and …And there you had it—another Victorian breathing contraption, albeit with a little less turbo power.

David’s heart was racing. Air! Our bodies were all about getting air! Flip the equation, as Dr.

Bramble had taught him, and you have this: getting air may have determined the way we got ourbodies.

God, it was so simple—and so mind-blowing. Because if David was right, he’d just solved thegreatest mystery in human evolution. No one had ever figured out why early humans had separatedthemselves from all creation by taking their knuckles off the ground and standing up. It was tobreathe! To open their throats, swell out their chests, and suck in air better than any other creatureon the planet.

But that was just the beginning. Because the better you are at breathing, David quickly realized,the better you are at—“Running? You’re saying humans evolved to go running?”

Dr. Dennis Bramble listened with interest as David Carrier explained his theory. Then he casuallytook aim and blew it to smithereens. He tried to be gentle; David was a brilliant student with atruly original mind, but this time, Bramble suspected, he’d fallen victim to the most commonmistake in science: the Handy Hammer Syndrome, in which the hammer in your hand makeseverything look like a nail.

Dr. Bramble knew a little about David’s life outside the classroom, and was aware that on sunnyspring afternoons, David loved to bolt from the labs and go trail-running in the WasatchMountains, which lap right up to the back of the University of Utah campus. Dr. Bramble was arunner himself, so he understood the attraction, but you had to be careful with stuff like that; abiologist’s biggest occupational hazard, second only to falling in love with your researchassistants, was falling in love with your hobbies. You become your own test subject; you startseeing the world as a reflection of your own life, and your own life as a reference point for justabout every phenomenon in the world.

“David,” Dr. Bramble began. “Species evolve according to what they’re good at, not what they’rebad at. And as runners, humans aren’t just bad—we’re awful.” You didn’t even need to get into thebiology; you could just look at cars and motorcycles. Four wheels are faster than two, because assoon as you go upright, you lose thrust, stability, and aerodynamics. Now transfer that design toanimals. A tiger is ten feet long and shaped like a cruise missile. It’s the drag racer of the jungle,while humans have to putter along with their skinny legs, tiny strides, and piss-poor windresistance.

“Yeah, I get it,” David said. Once we came up off our knuckles, everything went to hell. We lostraw speed and upper-body power—Good kid, Bramble thought. Learns quick.

But David wasn’t done. So why, David continued, would we give up strength and speed at thesame time? That left us unable to run, unable to fight, unable to climb and hide in the tree canopy.

We’d have been wiped out—unless we got something pretty amazing in exchange. Right?

That, Dr. Bramble had to admit, was a damn clever way to put the question. Cheetahs are fast butfrail; they have to hunt by day to avoid nocturnal killers like lions and panthers, and they abandontheir kills and run for cover when scrappy little thugs like hyenas show up. A gorilla, on the otherhand, is strong enough to lift a four-thousand-pound SUV, but with a gorilla’s land speed oftwenty miles per hour, that same SUV could run it over in first gear. And then we have humans,who are part cheetah, part gorilla—we’re slow and wimpy.

“So why would we evolve into a weaker creature, instead of a stronger one?” David persisted.

“This was long before we could make weapons, so what was the genetic advantage?”

Dr. Bramble played the scenario out in his head. He imagined a tribe of primitive hominids, allsquat, quick, and powerful, keeping their heads low for safety as they scrambled nimbly throughthe trees. One day, out pops a slow, skinny, sunken-chested son who’s barely bigger than a womanand keeps making a tiger target out of himself by walking around in the open. He’s too frail tofight, too slow to run away, too weak to attract a mate who’ll bear him children. By all logic, he’smarked for extinction—yet somehow, this dweeb becomes the father of all mankind, while hisstronger, swifter brothers disappear into oblivion.

That hypothetical account was actually a pretty accurate description of the Neanderthal Riddle.

Most people think Neanderthals were our ancestors, but they were actually a parallel species (orsubspecies, some say) that competed with Homo sapiens for survival. “Competed,” actually, isbeing kind; the Neanderthals had us beat any way you keep score. They were stronger, tougher,and probably smarter: they had burlier muscles, harder-to-break bones, better natural insulationagainst the cold, and, the fossil record suggests, a bigger brain. Neanderthals were fantasticallygifted hunters and skilled weapon-makers, and may very well have acquired language before wedid. They had a huge head start in the race for world domination; by the time the first Homosapiens appeared in Europe, Neanderthals had already been cozily established there for nearly twohundred thousand years. If you had to choose between Neanderthals and Early Us in a Last ManStanding contest, you’d go Neanderthal all the way.

So—where are they?

Within ten thousand years of the arrival of Homo sapiens in Europe, the Neanderthals vanished.

How it happened, no one knows. The only explanation is that some mysterious X Factor gave us—the weaker, dumber, skinnier creatures—a life-or-death edge over the Ice Age All-Stars. It wasn’tstrength. It wasn’t weapons. It wasn’t intelligence.

Could it have been running ability? Dr. Bramble wondered. Is David really onto something?

There was only one way to find out: go to the bones.

“At first I was very skeptical of David, for the same reason most morphologists would be,” Dr.

Bramble later told me. Morphology is basically the science of reverse engineering; it looks at howa body is assembled and tries to figure out how it’s supposed to function. Morphologists knowwhat to look for in a fast-moving machine, and in no way did the human body match the specs. Allyou had to do was look at our butts to figure that out. “In the whole history of vertebrates on Earth—the whole history—humans are the only running biped that’s tailless,” Bramble would later say.

Running is just a controlled fall, so how do you steer and keep from smacking down on your facewithout a weighted rudder, like a kangaroo’s tail?

“That’s what led me, like others, to dismiss the idea that humans evolved as running animals,”

Bramble said. “And I would have bought into the story and remained a skeptic, if I hadn’t alsobeen trained in paleontology.”

Dr. Bramble’s secondary expertise in fossils allowed him to compare how the human blueprint hadbeen modified over the millennia and check it against other designs. Right off the bat, he beganfinding things that didn’t fit. “Instead of looking at the conventional list, like most morphologists,and ticking off the things I expected to see, I began focusing on the abnormalities,” Bramble said.

“In other words, what’s there that shouldn’t be there?” He began by splitting the animal kingdominto two categories: runners and walkers. Runners include horses and dogs; walkers are pigs andchimps. If humans were designed to walk most of the time and run only in emergencies, ourmechanical parts should match up pretty closely to those of other walkers.

Common chimps were the perfect place to start. Not only are they a classic example of the walkinganimal, but they’re also our closest living relative; after more than six million years of separateevolution, we still share 95 percent of our DNA sequence with chimps. But what we don’t share,Bramble noted, is an Achilles tendon, which connects the calf to the heel: we’ve got one, chimpsdon’t. We have very different feet: ours are arched, chimps’ are flat. Our toes are short andstraight, which helps running, while chimps’ are long and splayed, much better for walking. Andcheck out our butts: we’ve got a hefty gluteus maximus, chimps have virtually none. Dr. Bramblethen focused on a little-known tendon behind the head known as the nuchal ligament. Chimpsdon’t have a nuchal ligament. Neither do pigs. Know who does? Dogs. Horses. And humans.

Now this was perplexing. The nuchal ligament is useful only for stabilizing the head when ananimal is moving fast; if you’re a walker, you don’t need one. Big butts are only necessary forrunning. (See for yourself: clutch your butt and walk around the room sometime. It’ll stay soft andfleshy, and only tighten up when you start to run. Your butt’s job is to prevent the momentum ofyour upper body from flipping you onto your face.) Likewise, the Achilles tendon serves nopurpose at all in walking, which is why chimps don’t have one. Neither did Australopithecus, oursemi-simian four-million-year-old ancestor; evidence of an Achilles tendon only began to appeartwo million years later, in Homo erectus.

Dr. Bramble then took a closer look at the skulls and got a jolt. Holy moly! he thought. There’ssomething going on here. The back of the Australopithecus skull was smooth, but when hechecked Homo erectus, he found a shallow groove for a nuchal ligament. A mystifying butunmistakable time line was taking shape: as the human body changed over time, it adopted keyfeatures of a running animal.

Weird, Bramble thought. How come we acquired all this specialized running stuff, and otherwalkers didn’t? For a walking animal, the Achilles would just be a liability. Moving on two legs islike walking on stilts; you plant your foot, pivot your body weight over the leg, and repeat. The lastthing you’d want would be stretchy, wobbly tendons right at your base of support. All an Achillestendon does is stretch like a rubber band—A rubber band! Dr. Bramble felt twin surges of pride and embarrassment. Rubber bands … Therehe’d been, thumping his chest about not being like all those other morphologists who “tick off thethings they expect to see,” when all along, he’d been just as misguided by myopia; he hadn’t eventhought about the rubber-band factor. When David started talking about running, Dr. Brambleassumed he meant speed. But there are two kinds of great runners: sprinters and marathoners.

Maybe human running was about going far, not fast. That would explain why our feet and legs areso dense with springy tendons—because springy tendons store and return energy, just like therubber-band propellers on balsa-wood airplanes. The more you twist the rubber band, the fartherthe plane flies; likewise, the more you can stretch the tendons, the more free energy you get whenthat leg extends and swings back.

And if I were going to design a long-distance running machine, Dr. Bramble thought, that’sexactly what I’d load it with—lots of rubber bands to maximize endurance. Running is really justjumping, springing from one foot to another. Tendons are irrelevant to walking, but great forenergy-efficient jumping. So forget speed; maybe we were born to be the world’s greatestmarathoners.

“And you’ve got to ask yourself why only one species in the world has the urge to gather by thetens of thousands to run twenty-six miles in the heat for fun,” Dr. Bramble mused. “Recreation hasits reasons.”

Together, Dr. Bramble and David Carrier began putting their World’s Greatest Marathoner modelto the test. Soon, evidence was turning up all over, even in places they weren’t looking. One oftheir first big discoveries came by accident when David took a horse for a jog. “We wanted tovideotape a horse to see how its gait coordinated with its breathing,” Dr. Bramble says. “Weneeded someone to keep the gear from getting tangled, so David ran alongside it.” When theyplayed back the tape, something seemed strange, although Bramble couldn’t figure out what it was.

He had to rewind a few times before it hit him: even though David and the horse were moving atthe same speed, David’s legs were moving more slowly.

“It was astonishing,” Dr. Bramble explains. “Even though the horse has long legs and four ofthem, David had a longer stride.” David was in great shape for a scientist, but as a medium-height,medium-weight, middle-of-the-pack runner, he perfectly average. That left only oneexplanation:asbizarreasitmayseem,theaveragehu(was) man has a longer stride than a horse. Thehorse looks like it’s taking giant lunges forward, but its hooves swing back before touching theground. The result: even though biomechanically smooth human runners have short strides, theystill cover more distance per step than a horse, making them more efficient. With equal amounts ofgas in the tank, in other words, a human can theoretically run farther than a horse.

But why settle for theory when you can put it to the test? Every October, a few dozen runners andriders face off in the 50-mile Man Against Horse Race in Prescott, Arizona. In 1999, a localrunner named Paul Bonnet passed the lead horses on the steep climb up Mingus Mountain andnever saw them again till after he’d crossed the finish line. The following year, Dennis Poolhecobegan a remarkable streak: he beat every man, woman, and steed for the next six years, until PaulBonnet wrested the title back in 2006. It would take eight years before a horse finally caught upwith those two and won again.

Discoveries like these, however, were just happy little extras for the two Utah scientists as theytunneled closer to their big breakthrough. As David had suspected on the day he peered into arabbit’s carcass and saw the history of life staring back at him, evolution seemed to be all aboutair; the more highly evolved the species, the better its carburetor. Take reptiles: David put lizardson a treadmill, and found they can’t even run and breathe at the same time. The best they canmanage is a quick scramble before stopping to pant.

Dr. Bramble, meanwhile, was working a little higher up the evolutionary ladder with big cats. Hediscovered that when many quadrupeds run, their internal organs slosh back and forth like water ina bathtub. Every time a cheetah’s front feet hit the ground, its guts slam forward into the lungs,forcing out air. When it reaches out for the next stride, its innards slide rearward, sucking air backin. Adding that extra punch to their lung power, though, comes at a cost: it limits cheetahs to justone breath per stride.

Actually, Dr. Bramble was surprised to find that all running mammals are restricted to the samecycle of take-a-step, take-a-breath. In the entire world, he and David could only find oneexception:


“When quadrupeds run, they get stuck in a one-breath-per-locomotion cycle,” Dr. Bramble said.

“But the human runners we tested never went one to one. They could pick from a number ofdifferent ratios, and generally preferred two to one.” The reason we’re free to pant to our heart’scontent is the same reason you need a shower on a summer day: we’re the only mammals that shedmost of our heat by sweating. All the pelt-covered creatures in the world cool off primarily bybreathing, which locks their entire heat-regulating system to their lungs. But humans, with ourmillions of sweat glands, are the best air-cooled engine that evolution has ever put on the market.

“That’s the benefit of being a naked, sweating animal,” David Carrier explains. “As long as wekeep sweating, we can keep going.” A team of Harvard scientists had once verified exactly thatpoint by sticking a rectal thermometer in a cheetah and getting it to run on a treadmill. Once itstemperature hit 105 degrees, the cheetah shut down and refused to run. That’s the natural responsefor all running mammals; when they build up more heat in their bodies than they can puff out theirmouths, they have to stop or die.

Fantastic! Springy legs, twiggy torsos, sweat glands, hairless skin, vertical bodies that retain lesssun heat—no wonder we’re the world’s greatest marathoners. But so what? Natural selection is allabout two things—eating and not getting eaten—and being able to run twenty miles ain’t worth adamn if the deer disappears in the first twenty seconds and a tiger can catch you in ten. What goodis endurance on a battlefield built on speed?

That’s the question Dr. Bramble was mulling in the early ’90s when he was on sabbatical and metDr. Dan Lieberman during a visit to Harvard. At the time, Lieberman was working on the otherend of the animal Olympics; he had a pig on a treadmill and was trying to figure out why it wassuch a lousy runner.

“Take a look at its head,” Bramble pointed out. “It wobbles all over the place. Pigs don’t have anuchal ligament.”

Lieberman’s ears perked up. As an evolutionary anthropologist, he knew that nothing on ourbodies has changed as much as the shape of our skulls, or says more about who we are. Even yourbreakfast burrito plays a role; Lieberman’s investigations had revealed that as our diet shifted overthe centuries from chewy stuff like raw roots and wild game and gave way to mushy cookedstaples like spaghetti and ground beef, our faces began to shrink. Ben Franklin’s face was chunkierthan yours; Caesar’s was bigger than his.

The Harvard and Utah scientists got along right from the start, mostly because of Lieberman’seyes: they didn’t roll when Bramble briefed him on the Running Man theory. “No one in thescientific community was willing to take it seriously,” Bramble said. “For every one paper onrunning, there were four thousand on walking. Whenever I’d bring it up at conferences, everyonewould always say, ‘Yeah, but we’re slow.’ They were focused on speed and couldn’t understandhow endurance could be an advantage.”

Well, to be fair, Bramble hadn’t really figured that one out yet, either. As biologists, he and DavidCarrier could decipher how the machine was designed, but they needed an anthropologist todetermine what that design could actually do. “I knew a lot about evolution and a little aboutlocomotion,” Lieberman says. “Dennis knew a shitload about locomotion, but not so much aboutevolution.”

As they traded stories and ideas, Bramble could tell that Lieberman was his kind of lab partner.

Lieberman was a scientist who believed that being hands-on meant being prepared to soak them inblood. For years, Lieberman had organized a Cro-Magnon barbecue on a Harvard Yard lawn aspart of his human evolution class. To demonstrate the dexterity necessary to operate primitivetools, he’d get his students to butcher a goat with sharpened stones, then cook it in a pit. As soon asthe aroma of roasting goat spread and the post-butchering libations began flowing, homeworkturned into a house party. “It eventually evolved into a kind of bacchanalian feast,” Lieberman toldthe Harvard University Gazette.

But there was an even more important reason that Lieberman was the perfect guy to tackle theRunning Man mystery: the solution seemed to be linked to his specialty, the head. Everyone knewthat at some point in history, early humans got access to a big supply of protein, which allowedtheir brains to expand like a thirsty sponge in a bucket of water. Our brains kept growing until theywere seven times larger than the brains of any comparable mammal. They also sucked up anungodly number of calories; even though our brains account for only 2 percent of our body weight,they demand 20 percent of our energy, compared with just 9 percent for chimps.

Dr. Lieberman threw himself into Running Man research with his usual creative zeal. Soon,students dropping by Lieberman’s office on the top floor of Harvard’s Peabody Museum werestartled to find a sweat-drenched one-armed man with an empty cream-cheese cup strapped to hishead running on a treadmill. “We humans are weird,” Lieberman said as he punched buttons on thecontrol panel. “No other creature has been found with a neck like ours.” He paused to shout aquestion to the man on the treadmill. “How much faster can you go, Willie?”

“Faster than this thing!” Willie called back, his steel left hand clanging against the treadmill rail.

Willie Stewart lost his arm when he was eighteen after a steel cable he was carrying on aconstruction job got caught in a whirling turbine, but he recovered to become a champion triathleteand rugby player. In addition to the cream-cheese cup, which being used to agyroscope,Williealsohadelectrodestapedtohischestandlegs.Dr.Lie(was) bermanhadrecruitedhim(secure) to test his theory that the human head, with its unique position directly on top of the neck, acts likethe roof weights used to prevent skyscrapers from pitching in the wind. Our heads didn’t justexpand because we got better at running, Lieberman believed; we got better at running because ourheads were expanding, thereby providing more ballast.

“Your head works with your arms to keep you from twisting and swaying in midstride,” Dr.

Lieberman said. The arms, meanwhile, also work as a counterbalance to keep the head aligned.

“That’s how bipeds solved the problem of how to stabilize a head with a movable neck. It’s yetanother feature of human evolution that only makes sense in terms of running.”

But the big mystery continued to be food. Judging by the Godzilla-like growth of our heads,Lieberman could pinpoint the exact moment when the caveman menu changed: it had to be twomillion years ago, when apelike Australopithecus—with his tiny brain, giant jaw, and billy-goatdiet of tough, fibrous plants—evolved into Homo erectus, our slim, long-legged ancestor with thebig head and small, tearing teeth perfectly suited for raw flesh and soft fruits. Only one thing couldhave sparked such a dramatic makeover: a diet no primate had ever eaten before, featuring areliable supply of meat, with its high concentrations of calories, fat, and protein.

“So where the fuck did they get it?” Lieberman asks, with all the gusto of a man who’s notsqueamish about hacking into goats with a rock. “The bow and arrow is twenty thousand years old.

The spearhead is two hundred thousand years old. But Homo erectus is around two million yearsold. That means that for most of our existence—-for nearly two million years!—hominids weregetting meat with their bare hands.”

Lieberman began playing the possibilities out in his mind. “Maybe we pirated carcasses killed byother predators?” he asked himself. “Scooting in and grabbing them while the lion was sleeping?”

No; that would give us an appetite for meat but not dependable access. You’d have to get to a killsite before the vultures, who can strip an antelope in minutes and “chew bones like crackers,” asLieberman likes to say. Even then, you might only tear off a few mouthfuls before the lion openeda baleful eye or a pack of hyenas drove you away.

“Okay, maybe we didn’t have spears. But we could have jumped on a boar and throttled it. Orclubbed it to death.”

Are you kidding? With all that thrashing and goring, you’d get your feet crushed, your testiclestorn, your ribs broken. You’d win, but you’d pay for it; break an ankle in the prehistoric wildernesswhile hunting for dinner, and you might become dinner yourself.

There’s no telling how long Lieberman would have remained stumped if his dog hadn’t finallygiven him the answer. One summer afternoon, Lieberman took Vashti, his mutty half border collie,for a five-mile jog around Fresh Pond. It was hot, and after a few miles, Vashti plopped downunder a tree and refused to move. Lieberman got impatient; yeah, it was a little warm, but not thatbad….

As he waited for his panting dog to cool off, Lieberman’s mind flashed back to his time doingfossil research in Africa. He recalled the shimmering waves across the sun-scorched savannah, theway the dry clay soaked up the heat and beamed it right back up through the soles of his boots.

Ethnographers’ reports he’d read years ago began flooding his mind; they told of African hunterswho used to chase antelope across the savannahs, and Tarahumara Indians who would race after adeer “until its hooves fell off.” Lieberman had always shrugged them off as tall tales, fables of agolden age of heroes who’d never really existed. But now, he started to wonder….

So how long would it take to actually run an animal to death? he asked himself. Luckily, theHarvard bio labs have the best locomotive research in the world (as their willingness to insert athermometer in a cheetah’s butt should make clear), so all the data Lieberman needed was right athis fingertips. When he got back to his office, he began punching in numbers. Let’s see, he began.

A jogger in decent shape averages about three to four meters a second. A deer trots at almost theidentical pace. But here’s the kicker: when a deer wants to accelerate to four meters a second, ithas to break into a heavy-breathing gallop, while a human can go just as fast and still be in hisjogging zone. A deer is way faster at a sprint, but we’re faster at a jog; so when Bambi is alreadyedging into oxygen debt, we’re barely breathing hard.

Lieberman kept looking, and found an even more telling comparison: the top galloping speed formost horses is 7.7 meters a second. They can hold that pace for about ten minutes, then have toslow to 5.8 meters a second. But an elite marathoner can jog for hours at 6 meters a second. Thehorse will erupt away from the starting line, as Dennis Poolheco had discovered in the ManAgainst Horse Race, but with enough patience and distance, you can slowly close the gap.

You don’t even have to go fast, Lieberman realized. All you have to do is keep the animal in sight,and within ten minutes, you’re reeling him in.

Lieberman began calculating temperatures, speed, and body weight. Soon, there it was before him:

the solution to the Running Man mystery. To run an antelope to death, Lieberman determined, allyou have to do is scare it into a gallop on a hot day. “If you keep just close enough for it to seeyou, it will keep sprinting away. After about ten or fifteen kilometers’ worth of running, it will gointo hyperthermia and collapse.” Translation: if you can run six miles on a summer day then you,my friend, are a lethal weapon in the animal kingdom. We can dump heat on the run, but animalscan’t pant while they gallop.

“We can run in conditions that no other animal can run in,” Lieberman realized. “And it’s not evenhard. If a middle-aged professor can outrun a dog on a hot day, imagine what a pack of motivatedhunter-gatherers could do to an overheated antelope.”

It’s easy to picture the scorn on the faces of those Masters of the Universe, the Neanderthals, asthey watched these new Running Men puffing along behind bouncy little Bambis, or jogging allday under a hot sun to return with nothing but an armload of yams. The Running Men could get aload of meat by running, but they couldn’t run with a belly load of meat, so most of the time theycarbo-loaded on roots and fruits, saving the antelope chops for special, calorie-boosting occasions.

Everyone scavenged together—Running Men, Running Women, Running Kids, and Grampies—but despite all that team activity, they were more likely to dine on grubs than wild game.

Bleh. Neanderthals wouldn’t touch bugs and dirt food; they ate meat and only meat, and not gristlylittle antelopes, either. Neanderthals went Grade A all the way: bears, bison, and elk marbled withjuicy fat, rhinos with livers rich in iron, mammoths with luscious, oily brains and bones drippingwith lip-smacking marrow. Try chasing monsters like those, though, and they’ll be chasing you.

Instead, you’ve got to outsmart and outfight them. The Neanderthals would lure them intoambushes and launch a pincer attack, storming from all sides with eight-foot wooden lances.

Hunting like that isn’t for the meek; Neanderthals were known to suffer the kind of injuries youfind on the rodeo circuit, neck and head trauma from getting thrown by bucking beasts, but theycould count on their band of brothers to care for their wounds and bury their bodies. Unlike ourtrue ancestors, those scampering Running Men, the Neanderthals were the mighty hunters we liketo imagine we once were; they stood shoulder to shoulder in battle, a united front of brains andbravery, clever warriors armored with muscle but still refined enough to slow-cook their meat totenderness in earth ovens and keep their women and children away from the danger.

Neanderthals ruled the world—till it started getting nice outside. About forty-five thousand yearsago, the Long Winter ended and a hot front moved in. The forests shrank, leaving behind parchedgrasslands stretching to the horizon. The new climate was great for the Running Men; the antelopeherds exploded and feasts of plump roots were pushing up all over the savannah.

The Neanderthals had it tougher; their long spears and canyon ambushes were useless against thefleet prairie creatures, and the big game they preferred was retreating deeper into the dwindlingforests. Well, why didn’t they just adopt the hunting strategy of the Running Men? They weresmart and certainly strong enough, but that the problem; they were too strong. Oncetemperaturesclimbabove90degreesFahrenheit,af(was) ew extra pounds of body weight make a hugedifference—so much so that to maintain heat balance, a 160- pound runner would lose nearly threeminutes per mile in a marathon against a one hundred-pound runner. In a two-hour pursuit of adeer, the Running Men would leave the Neanderthal competition more than ten miles behind.

Smothered in muscle, the Neanderthals followed the mastodons into the dying forest, and oblivion.

The new world was made for runners, and running just wasn’t their thing.

Privately, David Carrier knew the Running Man theory had a fatal flaw. The secret gnawed until itnearly turned him into a killer.

“Yeah, I was kind of obsessed,” he admitted when I met him at his lab in the University of Utah,twenty-five years and three academic degrees since his moment of inspiration at the dissectingtable in 1982. He was now David Carrier, Ph.D., professor of biology, with gray in his push-broommustache and rimless round glasses over his intense brown eyes. “I was dying to just grabsomething with my own two hands and say, ‘Look! Satisfied now?’”

The problem was this: Chasing an animal to death is evolution’s version of the perfect crime.

Persistence hunting (as it’s known to anthropologists) leaves behind no forensics—no arrowheads,no spear-nicked deer spines—so how do you build a case that a killing took place when you can’tproduce a corpse, a weapon, or witnesses? Despite Dr. Bramble’s physiological brilliance and Dr.

Lieberman’s fossil expertise, there was no way they could prove that our legs were once lethalweapons if they couldn’t show that someone, somewhere, had actually run an animal to death. Youcan spout any theory you want about human performance (“We can suspend our own heartbeats!

We can bend spoons with our brains!”) but in the end, you can’t make the shift from appealingnotion to empirical fact if you don’t come up with the goods.

“The frustrating thing is, we were finding stories all over the place,” David Carrier said. Throw adart at the map, and chances are you’ll bull’s-eye the site of a persistence-hunting tale. TheGoshutes and Papago tribes of the American West told them; so did the Kalahari Bushmen inBotswana, the Aborigines in Australia, Masai warriors in Kenya, the Seri and Tarahumara Indiansin Mexico. The trouble was, those legends were fourth-or fifth-hand at best; there was as muchevidence to support them as there was that Davy Crockett kilt him a b’ar when he was only three.

“We couldn’t find anyone who’d done a persistence hunt,” David said. “We couldn’t find someonewho’d even seen one.” No wonder the scientific community remained skeptical. If the RunningMan theory was right, then at least one person on this planet of six billion should still be able tocatch quarry on foot. We may have lost the tradition and necessity, but we should still have thenative ability: our DNA hasn’t changed in centuries and is 99.9 percent identical across the globe,meaning we’ve all got the same stock parts as any ancient hunter-gatherer. So how come none ofus could catch a stinking deer?

“That’s why I decided to do it myself,” David said. “As an under-grad, I got into mountain racesand had a lot of fun at those. So when it came to how humans breathe differently when we run, Ithink it was easier for me to see how it could affect us as a species. The idea didn’t seem as strangeto me as it would for someone who never left the lab.”

Nor did it seem strange to him that if he couldn’t find a caveman, he could become one. In thesummer of 1984, David persuaded his brother, Scott, a freelance writer and reporter for NationalPublic Radio, to go to Wyoming and help him catch a wild antelope. Scott wasn’t much of arunner, but David was in great shape and fiercely motivated by the lure of scientific immortality.

Between him and his brother, David figured, it should take only two hours before eight hundredpounds of proof was flopping at his feet.

“We drive off the interstate and down a dirt road for a few miles and it’s a wide and open highdesert of sagebrush, dry as a bone, mountains in every direction. There are antelope everywhere.”

That’s how Scott later painted the scene for listeners on NPR’s This American Life. “We stop thecar and start running after three—a buck and two does. They run very quickly, but for shortdistances, and then stop and stare at us till we catch up. Then they take off again. Sometimes theyrun a quarter of a mile, sometimes a half mile.”

Perfect! It was playing out exactly as David had predicted. The antelope weren’t getting enoughtime to cool off before David and Scott were yip-yip-yaahooing on their tails again. A few moremiles of this, David figured, and he’d be heading back to Salt Lake with a trunk full of venison anda killer video to slap down on Dr. Bramble’s desk. His brother, on the other hand, sensedsomething very different going on.

“The three antelope look at me like they know exactly what we’re proposing, and they’re not theleast bit worried,” Scott continues. It didn’t take him long to find out why they were so calm in theface of what should have been impending death. Instead of flopping over in exhaustion, theantelope pulled a shell game; when they got winded, they circled back and hid in the herd, leavingDavid and Scott no idea which antelopes were tired and which were fresh. “They blend and flowand change positions,” Scott says. “There are no individuals, but this mass that moves across thedesert like a pool of mercury on a glass table.”

For two more days, the two brothers chased mercury balls across the Wyoming plains, neverrealizing they were in the midst of a magnificent mistake. David’s failure was unwitting proof ofhis own theory: human running is different from any other running on earth. You can’t catch otheranimals by copying them, and especially not by using the crude approximation of animal runningwe’ve preserved in sports. David and Scott were relying on instinct, strength, and stamina, withoutrealizing that human distance running, at its evolutionary best, is much more than that; it’s a blendof strategy and skill perfected during millions of years of do-or-die decisions. And like any otherfine art, human distance running demands a brain-body connection that no other creature is capableof.

But it’s a lost art, as Scott Carrier would spend the next decade discovering. Something strangehappened out there on the Wyoming plains: the lure of the lost art got into Scott’s blood andwouldn’t let go. Despite the hopelessness of that expedition, Scott spent years researchingpersistence hunting on his brother’s behalf. He even created a nonprofit corporation devoted tofinding the Last of the Long Distance Hunters, and recruited elite ultrarunner Creighton King—theDouble Grand Canyon record holder before the Skaggs bros came along—to join an expedition tothe Sea of Cortez, where word had it that a tiny clan of Seri Indians had preserved the link to ourdistance-running past.

Scott found the clan—but he found them too late. Two elders had learned old-style running fromtheir father, but they were a half century out of practice and too old to even demonstrate.

That was the end of the trail. By 2004, the hunt for that one person in six billion had lasted twentyyears and gone nowhere. Scott Carrier gave up. David Carrier had moved on long before, and wasnow studying physical-combat structures in primates. The Last of the Long Distance Hunters was acold case.

Naturally, that’s when the phone rang.

“So, out of the blue, I find myself talking to this stranger,” Dr. Bramble begins. He looks like anold cowpoke, with his shaggy gray hair and crisp rancher’s shirt, and it’s a style that perfectlymatches the dried animal skulls on the walls of his lab and his enthralling, gather-round-thecampfirestorytelling. By 2004, Dr. Bramble says, the Utah-Harvard team had identified twenty-sixdistance-running markers on the human body. With little hope of ever finding the Last Hunter,they decided to go ahead and publish their findings anyway. Nature magazine put them on thecover, and a copy apparently made its way to a beach town on the South African coast, becausethat’s where this call was coming from.

“It’s not hard to run an antelope to death,” the stranger said. “I can show you how it’s done.”

“Sorry—who are you?”

“Louis Liebenberg. From Noordhoek.”

Bramble knew all the top names in the running-theory field, which wasn’t hard since they could fitaround a diner booth. Louis Liebenberg from Noordhoek he’d never heard of.

“Are you a hunter?” Bramble asked.

“Me? No.”

“Oh … anthropologist?”


“What’s your field?”

“Math. Math and physics.”

Math? “Uh … how did a mathematician run down an antelope?”

Bramble heard a snort of laughter. “By accident, mostly.”

It’s eerie how the lives of Louis Liebenberg and David Carrier spiraled each other for decadeswithout either of them knowing it. Back in the early ’80s, Louis was also an undergraduate incollege and, like David, he was suddenly electrified by an insight into human evolution that fewothers believed in.

Part of Louis’s problem was his expertise: he had none. At the time, he was barely twenty andmajoring in applied mathematics and physics at the University of Cape Town. It was while takingan elective course in the philosophy of science that he started wondering about the Big Bang of thehuman mind. How did we leap from basic survival thinking, like that of other animals, to wildlycomplicated concepts like logic, humor, deduction, abstract reasoning, and creative imagination?

Okay, so primitive man upgraded his hardware with a bigger brain—but where did he get thesoftware? Growing a bigger brain is an organic process, but being able to use that brain to projectinto the future and mentally connect, say, a kite, a key, and a lightning bolt and come up withelectrical transference was like a touch of magic. So where did that spark of inspiration comefrom?

The answer, Louis believed, was out in the deserts of southern Africa. Even though he was a citykid who knew jack about the outdoors, he had a hunch that the best place to look for the birth ofhuman thought was the place where human life began. “I had a vague gut feeling that the art ofanimal tracking could represent the origin of science itself,” Louis says. Then who better to studythan the Bushmen of the Kalahari Desert, who were both masters of animal tracking and livingremnants of our prehistoric past?

So, at age twenty-two, Louis decided to drop out of college and write a new chapter in naturalhistory by testing his theory with the Bushmen. It was an insanely ambitious plan for a collegedropout with zero experience in anthropology, wilderness survival, or scientific method. He spokeneither the Bushmen’s native tongue, !Kabee, nor their adopted one, Afrikaans. He didn’t evenknow anything about animal tracking, the reason he was going in the first place. But so what?

Louis shrugged, and got to work. He found an Afrikaans translator, made contact with huntingguides and anthropologists, and eventually set off down the Trans-Kalahari Highway intoBotswana, Namibia … and the unknown.

Like Scott Carrier, Louis soon discovered that he was losing a race against time. “I went village tovillage looking for Bushmen who hunt with bow and arrow, since they’d have the tracking skills,”

Louis says. But with big-game safaris and ranchers taking over their old game lands, most of theBushmen had abandoned the nomadic life and were living on government settlements. Theirdecline heartbreaking; instead of roaming the wilderness, many of the Bushmensurvivingon(was) slave wages for farm jobs and seeing their sisters and daughters recruited by truck-(were) stop bordellos.

Louis kept searching. Far out in the Kalahari, he finally came across a renegade band of Bushmenwho, he says, “stubbornly clung to freedom and independence and wouldn’t subject themselves tomanual labor or prostitution.” As it turned out, the search for One in Six Billion was just aboutmathematically correct: in all the Kalahari, only six true hunters remained.

The renegades agreed to let Louis hang around, an offer he took to the extreme; once installed,Louis acted like an unemployed in-law, basically squatting with the Bushmen for the next fouryears. The city kid from Cape Town learned to live on the Bushman diet of roots, berries,porcupine, and ratlike springhares. He learned to keep his campfire burning and tent zipped evenon the most sweltering nights, since packs of hyenas were known to drag people from openshelters and tear out their throats. He learned that if you stumble upon an angry lioness and hercubs, you stand tall and make her back down, but in the same situation with a rhino, you run likehell.

When it comes to mentors, you can’t beat survival; just trying to fill his belly every day and avoidpissing off, for instance, two black-backed jackals mating beneath a baobob was an excellent wayfor Louis to begin absorbing the wizardry of a master tracker. He learned to look at piles of zebradung and distinguish which droppings came from which animal; intestines, he discovered, haveridges and grooves that leave unique patterns on feces. Learn to tell them apart, and you can singleout a zebra from an exploding herd and track it for days by its distinctive droppings. Louis learnedto hunch over a set of fox tracks and re-create exactly what it was doing: here, it was movingslowly as it scented around for mice and scorpions, and look, that’s where it trotted off withsomething in its mouth. A swirl of swept dirt told him where an ostrich had taken a dust bath, andlet him backtrack to find its eggs. Meerkats make their warrens in hard-pan, so why were theydigging here in soft sand? Must mean there’s a den of tasty scorpions….

Even after you learn to read dirt, you ain’t learned nothing; the next level is tracking withouttracks, a higher state of reasoning known in the lit as “speculative hunting.” The only way you canpull it off, Louis discovered, was by projecting yourself out of the present and into the future,transporting yourself into the mind of the animal you’re tracking. Once you learn to think likeanother creature, you can anticipate what it will do and react before it ever acts. If that sounds alittle Hollywood, then you’ve seen your share of movies about impossibly clairvoyant FBIprofilers who can “see with the eyes of a killer.” But out there on the Kalahari plains, mind-throwing was a very real and potentially deadly talent.

“When tracking an animal, one attempts to think like an animal in order to predict where it isgoing,” Louis says. “Looking at its tracks, one visualizes the motion of the animal and feels thatmotion in one’s own body. You go into a trancelike state, the concentration is so intense. It’sactually quite dangerous, because you become numb to your own body and can keep pushingyourself until you collapse.”

Visualization … empathy … abstract thinking and forward projection: aside from the keeling-overpart, isn’t that exactly the mental engineering we now use for science, medicine, the creative arts?

“When you track, you’re creating causal connections in your mind, because you didn’t actually seewhat the animal did,” Louis realized. “That’s the essence of physics.” With speculative hunting,early human hunters had gone beyond connecting the dots; they were now connecting dots thatexisted only in their minds.

One morning, four of the renegade Bushmen—!Nate, !Nam!kabe, Kayate, and Boro/xao—wokeLouis up before dawn to invite him on a special hunt. Don’t eat any breakfast, they warned him,and drink all the water you can hold. Louis downed a mug of coffee, grabbed his boots, and fell inbehind the hunters as they marched off across the savannah in the dark. The sun rose until it wasbroiling over their heads, but the hunters pushed on. Finally, after walking nearly twenty miles,they spotted a clutch of kudu, an especially agile form of antelope. That’s when the Bushmenstarted to run.

Louis stood there, confused. He knew the standard Bushman bow-hunting drill: drop to your belly,creep into arrow range, let fly. So what the hell was this all about? He’d heard a little aboutpersistence hunts, but he ranked them somewhere between an accident and a lie: either the animalhad actually broken its neck while fleeing, or the story was out-and-out baloney. No way theseguys were going to catch one of those kudus on foot. No way. But the more he said “No way,” thefarther away the Bushmen got, so Louis quit thinking and started running.

“This is how we do it,” !Nate said when a panting Louis caught up. The four hunters ran swiftlybut easily behind the bounding kudu. Whenever the animals darted into an acacia grove, one of thehunters broke from the group and drove the kudu back into the sun. The herd would scatter, reform,scatter again, but the four Bushmen ran and swerved behind a single kudu, cutting it out ofthe herd whenever it tried to blend, flushing it from the trees whenever it tried to rest. If they had adoubt about which one to chase, they dropped to the ground, checked the tracks, and adjusted theirpursuit.

As he gasped along behind the band, Louis was surprised to find !Nate, the strongest and mostskilled hunter of the renegade Bushmen, hanging back with him. !Nate wasn’t even carrying acanteen like the other hunters. Nearly ninety minutes into the pursuit, Louis discovered why: whenone of the older hunters tired and dropped out, he handed his canteen to !Nate. !Nate drank it dry,then traded it for a half-full one when a second runner dropped out.

Louis staggered along behind, determined to see the hunt through to the end. He was bitterlyregretting his choice of heavy bush boots; the Bushmen traditionally wore light, giraffe-skinmoccasins, and now had on thin, flimsy sneakers that let their feet cool on the fly. Louis felt theway the kudu looked; he watched it weave drunkenly … its front knees buckled, straightened … itrecovered and bounded away … then crashed to the ground.

So did Louis. By the time he got to the fallen kudu, he was so overheated he’d stopped sweating.

He pitched facedown into the sand. “When you’re focused on the hunt, you push to the limits.

You’re not aware you’re exhausted,” Louis later explained. In a way, he’d triumphed; Louis hadmanaged to cross over and run as hard as if he were the one being pursued. Where he failed wasnot knowing to check his own footprints; because it’s so easy to become numb to your own vitalsigns, the Bushmen learned long ago to periodically check their own tracks. If their prints lookedas bad as the kudu’s, they’d stop, wash their faces, hold a mouthful of water and slowly let ittrickle down their throats. After the final swallow, they’d walk and check their tracks again.

Louis’s head was pounding and his dry eyes were going blurry. He was barely conscious, but stillalert enough to be really scared; he was lying in the desert in 107- degree heat, and he knew he hadonly one chance to save his life. He fumbled for his belt knife and reached toward the dead kudu.

If he could slash it open, he could suck the water from its stomach.

“NO!” !Nate stopped Louis. Unlike other antelopes, kudus eat acacia leaves, which are poisonousfor humans. !Nate calmed Louis, told him to hold on a little longer, and took off running: eventhough !Nate had already hiked twenty miles and run fifteen, he was able to run twelve more milesto bring Louis back some water. !Nate wouldn’t let him drink it. First, he rinsed Louis’s head, thenhe washed his face, and only after Louis’s skin began to cool did !Nate allow him tiny sips.

Later, after !Nate had helped him back to camp, Louis marveled at the ruthless efficiency of thepersistence hunt. “It’s much more efficient than a bow and arrow,” he observed. “It takes a lot ofattempts to get a successful hunt by bow. You can hit the animal and still lose it, or scavengers cansmell blood and get to it before you do, or it can take all night for the poison on the arrow tips towork. Only a small percentage of arrow shots are successful, so for the number of days hunting,the meat yield of a persistence hunt is much higher.”

Louis found out only in his second, third, and fourth persistence hunts how lucky he’d gotten in thefirst; that debut kudu dropped after only two hours, but every one after that kept the Bushmen onthe run for three to five hours (neatly corresponding, one might note, to how long it takes mostpeople to run our latter-day version of prehistoric hunting, the marathon. Recreation has itsreasons).

To succeed as a hunter, Louis had to reinvent himself as a runner. He’d been an excellent middle-distance athlete in high school, winning the 1,500-meter championship and finishing a closesecond in the 800, but to hang with the Bushmen, he had to forget everything he’d been taught bymodern coaches and study the ancients. As a track athlete, he’d drop his head and hammer, but asan apprentice Bushman, he had to be eyes high and tinglingly alert every step of the way. Hecouldn’t zone out and ignore pain; instead, his mind was constantly tap-dancing between theimmediate—scratches in the dust, sweat on his own forehead—and the imaginary, as he playedmental war games to think one step ahead of his prey.

The pace wasn’t too fierce; the Bushmen average about ten minutes a mile, but many of thosemiles are in soft sand and brush, and they occasionally stop to study tracks. They’d still fire the jetsand take off at a sprint, but they knew how to keep trotting afterward and recover on the run. Theyhad to, because a persistence hunt was like showing up at the starting line without knowing if youwere running a half marathon, marathon, or ultra. After a while, Louis began to look at running theway other people look at walking; he learned to settle back and let his legs spin in a quick, easytrot, a sort of baseline motion that could last all day and leave him enough reserves to acceleratewhen necessary.

His eating changed, too. As a hunter-gatherer, you’re never off the clock; you can be walkinghome after an exhausting day of collecting yams, but if fresh game scuttles into view, you dropeverything and go. So Louis had to learn to graze, eating lightly throughout the day rather thanfilling up on big meals, never letting himself get thirsty, treating every day as if he were in a racethat had already started.

The Kalahari summer cooled into winter, but the hunts continued. The Utah-Harvard docs wouldturn out to be wrong about one part of their Running Man theory: persistence hunting doesn’tdepend on killer heat, because the ingenious Bushmen had devised ways to run down game inevery weather. In the rainy season, both the tiny duiker antelope and the giant gemsbok, with itslancelike horns, would overheat because the wet sand splayed their hooves, forcing their legs tochurn harder. The four-hundred-pound red hartebeest is comfortable in waist-high grasslands, butexposed and vulnerable when the ground parches during dry winters. Come the full moon,antelopes are active all night and tired by daybreak; come spring, they’re weakened by diarrheafrom feasting on green leaves.

By the time Louis was ready to head home from the bush and begin writing The Art of Tracking:

The Origin of Science, he’d gotten so accustomed to epic runs that he almost took them forgranted. He barely mentions running in his book, focusing more on the mental demands of the huntthan the physical. It was only after a copy of Nature magazine fell into his hands that he fullyappreciated what he’d seen out there in the Kalahari, and grabbed the phone to dial Utah.

Know why people run marathons? he told Dr. Bramble. Because running is rooted in our collectiveimagination, and our imagination is rooted in running. Language, art, science; space shuttles,Starry Night, intravascular surgery; they all had their roots in our ability to run. Running was thesuperpower that made us human—which means it’s a superpower all humans possess.

“Then why do so many people hate it?” I asked Dr. Bramble as he came to the end of the story ofLouis and the Bushmen. “If we’re all born to run, shouldn’t all of us enjoy it?”

Dr. Bramble began his answer with a riddle. “This is fascinating stuff,” he said. “We monitored theresults of the 2004 New York City Marathon and compared finishing times by age. What we foundis that starting at age nineteen, runners get faster every year until they hit their peak at twenty-seven. After twenty-seven, they start to decline. So here’s the question—how old are you whenyou’re back to running the same speed you did at nineteen?”

All righty. I flipped my notebook to a blank page and started jotting numbers. It takes eight yearsuntil you run your best time at age twenty-seven. If you get slower at the same rate you got faster,then you’d be back at your nineteen-year-old time by age thirty-six: eight years up, eight yearsdown. But I knew there was a twist involved, and I was pretty sure it had to be whether we fadeaway as quickly as we improve. “We probably hang on to our speed a little longer once we get it,”

I decided. Khalid Khannouchi was twenty-six when he broke the marathon world record, and wasstill fast enough at thirty-six to finish in the top four at the 2008 U.S. Olympic trials. He’d lost onlyten minutes in ten years, despite a ton of injuries. In honor of the Khannouchi Curve, I bumped myanswer up to forty.

“Forty—,” I started to say, until I saw the smile creasing Bramble’s face. “Five,” I hastily added.

“I’ll guess forty-five.”




“It can’t be fifty-five.”

“You’re right,” Bramble said. “It can’t be. It’s sixty-four.”

“Are you serious? That’s a—” I scribbled out the math. “That’s a forty-five-year difference.

You’re saying teenagers can’t beat guys three times their age?”

“Isn’t that amazing?” Bramble agreed. “Name any other field of athletic endeavor where sixtyfour-year-olds competing with nineteen-year-olds. Swimming? Boxing? Not even close.

There’ssomething(are) really weird about us humans; we’re not only really good at endurance running,we’re really good at it for a remarkably long time. We’re a machine built to run—and the machinenever wears out.”

You don’t stop running because you get old, the Dipsea Demon always said. You get old becauseyou stop running….

“And it’s true for both genders,” Dr. Bramble continued. “Women show the same results as men.”

That makes sense, since a curious transformation came over us when we came down from thetrees: the more we became human, the more we became equal. Men and women are basically thesame size, at least compared with other primates: male gorillas and orangutans weigh twice asmuch as their better halves; male chimps are a good one-third bigger than females; but between theaverage human him and the average human her, the difference in bulk is only a slim 15 percent. Aswe evolved, we shucked our beef and became more sinuous, more cooperative … essentially, morefemale.

“Women have really been underrated,” Dr. Bramble said. “They’ve been evolutionarilyshortchanged. We perpetuate this notion that they were sitting around waiting for the men to comeback with food, but there’s no reason why women couldn’t be part of the hunting party.” Actually,it would be weird if women weren’t hunting alongside the men, since they’re the ones who reallyneed the meat. The human body benefits most from meat protein during infancy, pregnancy, andlactation, so why wouldn’t women get as close to the beef supply as possible? Hunter-gatherernomads shift their camps by the movements of the herds, so instead of hauling food back to camp,it made more sense for the whole camp to go to the food.

And caring for kids on the fly isn’t that hard, as American ultra-runner Kami Semickdemonstrates; she likes to run mountain trails around Bend, Oregon, with her four-year-olddaughter, Baronie, riding along in a backpack. Newborns? No problem: at the 2007 Hardrock 100,Emily Baer beat ninety other men and women to finish eighth overall while stopping at every aidstation to breast-feed her infant son. The Bushmen are no longer nomadic, but the equal-partnersin-hunting tradition still exists among the Mbuti Pygmies of the Congo, where husbands and wiveswith nets pursue the giant forest hog side by side. “Since they are perfectly capable of giving birthto a child while on the hunt, then rejoining the hunt the same morning,” notes anthropologist ColinTurnbull, who’s spent years among the Mbuti, “mothers see no reason why they should notcontinue to participate fully”

Dr. Bramble’s picture of the past was taking on clarity and color. I could see a band of hunters—young and old, male and female—running tirelessly across the grasslands. The women are upfront, leading the way toward fresh tracks they spotted while foraging, and hard behind are the oldmen, their eyes on the ground and their minds inside a kudu skull a half mile ahead. Crowdingtheir heels are teens eager to soak up tips. The real muscle hangs back; the guys in their twenties,the strongest runners and hunters, watching the lead trackers and saving their strength for the kill.

And bringing up the rear? The Kami Semicks of the savannah, toting their kids and grandkids.

After all, what else did we have going for us? Nothing, except we ran like crazy and stucktogether. Humans are among the most communal and cooperative of all primates; our sole defensein a fang-filled world was our solidarity, and there’s no reason to think we suddenly disbandedduring our most crucial challenge, the hunt for food. I remembered what the Seri Indians told ScottCarrier after the sun had set on their persistence-hunting days. “It was better before,” a Seri elderlamented. “We did everything as a family. The whole community was a family. We sharedeverything and cooperated, but now there is a lot of arguing and bickering, every man for himself.”

Running didn’t just make the Seris a people. As Coach Joe Vigil would later sense about his ownathletes, it also made them better people.

“But there’s a problem,” Dr. Bramble said. He tapped his forehead. “And it’s right up here.” Ourgreatest talent, he explained, also created the monster that could destroy us. “Unlike any otherorganism in history, humans have a mind-body conflict: we have a body built for performance, buta brain that’s always looking for efficiency.” We live or die by our endurance, but remember:

endurance is all about conserving energy, and that’s the brain’s department. “The reason somepeople use their genetic gift for running and others don’t is because the brain is a bargain shopper.”

For millions of years, we lived in a world without cops, cabs, or Domino’s Pizza; we relied on ourlegs for safety, food, and transportation, and it wasn’t as if you could count on one job endingbefore the next one began. Look at !Nate’s wild hunt with Louis; !Nate sure wasn’t planning on afast 10k immediately after a half-day hike and a high-speed hunt, but he still found the reserveenergy to save Louis’s life. Nor could his ancestors ever be sure that they wouldn’t become foodright after catching some; the antelope they’d chased since dawn could attract fiercer animals,forcing the hunters to drop lunch and run for their lives. The only way to survive was to leavesomething in the tank—and that’s where the brain comes in.

“The brain is always scheming to reduce costs, get more for less, store energy and have it ready foran emergency,” Bramble explained. “You’ve got this fancy machine, and it’s controlled by a pilotwho’s thinking, ‘Okay, how can I run this baby without using any fuel?’ You and I know howgood running feels because we’ve made a habit of it.” But lose the habit, and the loudest voice inyour ear is your ancient survival instinct urging you to relax. And there’s the bitter irony: ourfantastic endurance gave our brain the food it needed to grow, and now our brain is underminingour endurance.

“We live in a culture that sees extreme exercise as crazy,” Dr. Bramble says, “because that’s whatour brain tells us: why fire up the machine if you don’t have to?”

To be fair, our brain knew what it was talking about for 99 percent of our history; sitting aroundwas a luxury, so when you had the chance to rest and recover, you grabbed it. Only recently havewe come up with the technology to turn lazing around into a way of life; we’ve taken our sinewy,durable, hunter-gatherer bodies and plunked them into an artificial world of leisure. And whathappens when you drop a life-form into an alien environment? NASA scientists wondered thesame thing before the first space flights. The human body had been built to thrive under thepressure of gravity, so maybe taking away that pressure would act as an escape-trajectory Fountainof Youth, leaving the astronauts feeling stronger, smarter, and healthier. After all, every caloriethey ate would now go toward feeding their brains and bodies, instead of pushing up against thatrelentless downward pull—right?

Not by a long shot; by the time the astronauts returned to earth, they’d aged decades in a matter ofdays. Their bones were weaker and their muscles had atrophied; they had insomnia, depression,acute fatigue, and listlessness. Even their taste buds had decayed. If you’ve ever spent a longweekend watching TV on the sofa, you know the feeling, because down here on earth, we’vecreated our own zero-gravity bubble; we’ve taken away the jobs our bodies were meant to do, andwe’re paying for it. Nearly every top killer in the Western world—heart disease, stroke, diabetes,depression, hypertension, and a dozen forms of cancer—was unknown to our ancestors. Theydidn’t have medicine, but they did have a magic bullet—or maybe two, judging by the number ofdigits Dr. Bramble was holding up.

“You could literally halt epidemics in their tracks with this one remedy,” he said. He flashed twofingers up in a peace sign, then slowly rotated them downward till they were scissoring throughspace. The Running Man.

“So simple,” he said. “Just move your legs. Because if you don’t think you were born to run,you’re not only denying history. You’re denying who you are.”