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:

You.

“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 &ldq............