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As it turned out, that would be dinosaurs. In fact, Nopcsa became interested in dinosaurs before he knew anything of Albania, before he met Doda. When he was eighteen, his sister picked up a mangled skull on the family estate. The bones had turned to stone, and it didn’t look like any animal the young baron had ever seen scurrying or soaring across his stately grounds. He brought it with him when he started university in Vienna later that year, and upon showing it to one of his geology instructors, he was told to go find more. And so he did, obsessively exploring the fields, hills, and riverbeds of the land he would later inherit, on foot and horseback. Four years later, a blueblood in name but still just a student, he stood up in front of the learned men of the Austrian Academy of Sciences and announced what he had been up to and what he had found: a whole ecosystem of strange dinosaurs. Nopcsa continued to collect Transylvanian dinosaurs for much of the rest of his life, taking breaks here and there when his services were needed in Albania. He studied them, too, and in doing so was one of the first people who made any attempt to grasp what dinosaurs were like as real animals, not simply bones to be classified. He had a genius when it came to interpreting fossils, and it didn’t take him very long to notice that something was odd about the bones he was finding on his estate. He could tell that they belonged to groups that were common in other parts of the world—a new species that he named Telmatosaurus was a duckbill, a long-necked critter called Magyarosaurus was a sauropod, and he also found the bones of armored dinosaurs. However, they were smaller than their mainland relatives, in some cases, astoundingly so; while its cousins were shaking the Earth with their thirty-ton frames in Brazil, Magyarosaurus was barely the size of a cow. At first Nopcsa thought the bones belonged to juveniles, but when he put them under a microscope, he realized that they had the characteristic textures of adults. There was only one suitable explanation: these Transylvanian dinosaurs were miniatures. This raised an obvious question: why were they so tiny? Nopcsa had an idea. Along with his expertise in espionage, linguistics, cultural anthropology, paleontology, motorbiking, and general scheming, the baron was also a very good geologist. He mapped the rocks that held the dinosaur fossils and could tell that they had formed in rivers—thick sequences of sandstones and mudstones that were deposited either in the channels or off to the side when the rivers flooded. Underneath these rocks were other layers that came from the ocean—fine clays and shales bursting with microscopic plankton fossils.


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Tracing out the aerial extent of the river rocks and scrutinizing the contacts between the river and ocean layers, Nopcsa realized that his estate used to be part of an island, which emerged from the water some time during the latest Cretaceous. The mini-dinosaurs were living on a small bit of turf, probably around thirty thousand square miles (eighty thousand square kilometers) in area, about the size of Hispaniola. Maybe, Nopcsa conjectured, the dinosaurs were small because of their island habitat. It stemmed from an idea that some biologists of the time were beginning to entertain, based on studies of modern species living on islands and the discovery of some strange small mammal fossils in the middle of the Mediterranean. This theory held that islands are akin to laboratories of evolution, where some of the normal rules that govern larger landmasses break down. Islands are remote, so it is always a little bit random as to which species can make their way out to them, being carried by the wind or rafting in on floating logs. There is less space on islands, so fewer resources, so some species may not be able to get so big. And, because islands are severed from the mainland, their plants and animals can evolve in splendid isolation, their DNA cut off from that of their continental cousins, each inbred island-living generation becoming more different, more peculiar over time. This, Nopcsa, thought, is why his island-dwelling dinosaurs were so tiny, so funny looking. Later research showed that Nopcsa was correct, and his dwarf dinosaurs are now regarded as a prime example of the “island effect” in action. Otherwise, fate wasn’t so kind to the baron. Austria-Hungary was on the losing side in the Great War, and Transylvania was handed over to one of the winners, Romania. Nopcsa lost his lands and his castle, and a senseless attempt to reclaim his estate ended with him getting pummeled by a gang of peasants and left for dead by the side of the road. With little money to support his lavish lifestyle, Nopcsa grudgingly accepted the directorship of the Hungarian Geological Institute in Budapest, but bureaucratic life was not for him, so he quit. He sold off his fossils and moved to Vienna with Doda, destitute and overcome with a melancholy that we would probably today recognize as depression. Eventually he had enough. In April 1933, the erstwhile baron slipped some sedative into his lover’s tea. When Doda drifted off to sleep, Nopcsa put a bullet into him, then turned the gun on himself. Nopcsa’s tragic demise left one mystery. The baron had cracked the riddle of the island dinosaurs, and he knew why they were small, but almost every bone he found—whether sauropod, duckbill, or armored ankylosaur—came from a plant-eater. He had little clue as to what predators prowled his miniature menagerie. Were there freakish versions of tyrannosaurs or carcharodontosaurs that ruled the island, perhaps ones that skipped over from the continents?


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Other types of meat-eaters, also of diminutive stature? Or maybe there were no carnivores at all—the herbivores able to shrink in size because there was nothing out there hunting them. Solving this problem took a century and another remarkable character, a Transylvanian cut from the same cloth as Nopcsa. Mátyás Vremir is also a polymath, a man of many languages, a traveler who sets out for strange lands with little more than his rucksack. He’s never been a spy—as far as I know—but for many years he hopscotched around Africa, working on oil rigs and scouting new drill sites. Now he runs his own company in his native city of Cluj-Napoca, doing environmental surveys and geological consulting on building projects. He’s also into many other things: skiing and exploring caves in the Carpathians, canoeing the Danube Delta, and rock climbing, often bringing along his wife and two young sons (in this custom, he departs from Nopcsa). Tall and wiry, with the long hair of a rocker and the piercing eyes of a wolf, he has an intense personal code of honor and does not suffer fools gladly—or really, at all—but if he likes and respects you, he will go to war with you. He’s one of my favorite people in the world. If I ever found myself in any real danger, in any godforsaken corner of the planet, he’s the one person whom I would want by my side, a man I know I could trust with my life. He has many talents, but what Mátyás does best is find dinosaurs. Along with my friend Grzegorz from Poland, who found all of those footprints of the first dinosauromorphs, Mátyás has the best nose for fossils of anybody I’ve ever known. And he seems to do it so effortlessly; when we’re together in Romania, me all festooned in my pricey field gear and Mátyás strolling along in his board shorts, cigarette dangling from his lips, it’s always he who sees the good fossils. But it isn’t really that easy. Mátyás is in fact ruthless: when on the scent of fossils, he’ll wade into frigid rivers in the Romanian winter, abseil down hundred-foot cliffs, or contort himself into the tightest and deepest of caves. Once I saw him push his way through rapids on a broken foot because he saw a bone sticking out of the opposite riverbank. At that very same river, in autumn 2009, Mátyás made the most important discovery of his life. He was out prospecting with his boys when he saw some chalk-white lumps poking out from the rusty red rocks on the bank a few feet above the waterline. Bones. He took out his tools and scratched into the soft mudrock, and more kept coming: the limbs and torso of a poodle-size critter. Excitement quickly turned to fear: the local power station would soon be discharging a surge of water into the river, and the rising currents would probably wash away the bones.


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So Mátyás worked quickly, but with the precision of a surgeon, and cut the skeleton out of its 69-million-year-old tomb. He brought it back to Cluj-Napoca, made sure it was kept safe in the local museum, and then got down to trying to figure out what it was. He was pretty sure it was a dinosaur, but nothing like it had been found in Transylvania before. Some outside advice would be useful, so Mátyás e-mailed a paleontologist who had excavated and described a great variety of small Late Cretaceous dinosaurs: Mark Norell, the dinosaur curator at the American Museum of Natural History in New York, the guy with Barnum Brown’s old job. Like me, Mark gets a lot of random e-mails from people asking him to identify their fossils, which often are nothing more than misshapen rocks or lumps of concrete. But when he opened the e-mail from Mátyás and downloaded the photos that were attached, Mark was gobsmacked. I know because I was there. I was Mark’s PhD student at the time, writing a thesis on theropod dinosaur genealogy and evolution. Mark called me into his office—a stately suite looking out over Central Park—and asked what I thought about the cryptic message he had just received from Romania. We both agreed the bones looked like a theropod’s, and when we did a bit of research, we realized that no good meat-eating dinosaur skeletons had ever been found in Transylvania. Mark replied to Mátyás and they struck up a friendship, and a few months later, the three of us found ourselves together in the February chill of Bucharest. We convened in the wood-paneled office of one of Mátyás’s colleagues, a thirty-something professor named Zoltán Csiki-Sava, who, after the fall of Communism put an end to his forced conscription in Ceaușescu’s army, went to college and became one of Europe’s top dinosaur experts. All of the bones were laid out before us on a table, and it was up to us four to identify them. Seeing the specimen with our own eyes, we had no doubt it was a theropod. Many of its light, delicate bones resembled those of Velociraptor and other lithe, fierce raptor species. It was about the same size as Velociraptor, too, or maybe a tad smaller. But something didn’t quite fit. Mátyás’s dinosaur had four big toes on each foot, the two inner ones bearing huge, sickle-shaped claws. The raptors were famous for their retractable sickle claws—which they used to slash and gut their prey—but they had only one on each foot. Besides, they had only three main toes, not four. We were stuck in a quandary, and it seemed that we might have a new dinosaur on our hands. Mátyás Vremir surveying the Red Cliffs in Transylvania, on the lookout for fossils of dwarfed dinosaurs. Photo courtesy of the author Over the course of the week, we kept studying the bones, measuring and comparing them to the skeletons of other dinosaurs. Finally it dawned on us.


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This new Romanian theropod was a raptor, but a peculiar one, with extra toes and claws compared to its mainland relatives. This was quite the revelation: while the plant-eating dinosaurs of the ancient Transylvanian island got small, the predators went weird. It wasn’t just the double set of killer claws and the extra toe. The Romanian raptor was stockier than Velociraptor, many of the bones of its arms and legs were fused together, and it had even withered its hand into a conjoined mass of stubby fingers and wristbones. It was a new breed of meat-eating dinosaur, and a few months later we gave it a fitting scientific name: Balaur bondoc; the first word is an archaic Romanian term for dragon and the second means “stocky.” Balaur bondoc was the top dog of the Late Cretaceous European islands. Less tyrant than assassin, Balaur would employ its arsenal of claws to subdue the cow-size sauropods and mini-duckbills and armored dinosaurs marooned in the middle of the rising Atlantic. As best we can tell, it was the largest carnivorous dinosaur on the islands. Who knows what fossils Mátyás will find next, but it seems fairly certain he’ll never come across a giant tyrannosaurish carnivore. After a century of searching, after the collection of thousands of fossils—of not only bones but also eggs and footprints, and not only dinosaurs but also lizards and mammals—not a single scrap of a big flesh-eater has ever turned up. Not even a tooth. That absence is probably telling us something: the island was too small to support giant bone-crunching monsters, so it was the feisty little guys like Balaur that topped the food chain—another sign of just how unusual these most stupendous of dinosaur ecosystems were during the closing years of the Cretaceous. The foot of Balaur, the tiny top predator of the latest Cretaceous Transylvanian island. Photograph by Mick Ellison. ON ONE OF my trips to Transylvania, we took the afternoon off from fossil hunting and headed into the hills. Mátyás stopped the car outside a castle, near a small village called Săcel. It must have been grand once, but now it was falling to ruin, abandoned long ago. Most of the bright green paint on the outside had faded, exposing the bricks. The windows were all busted, the wooden floors were decaying, and the plaster was sprayed with graffiti. Feral dogs wandered about like zombies. Dust clung to every surface. But somehow, as if defying the laws of gravity and the ravages of time, a gilded chandelier hung proudly from the ceiling in the foyer. We walked underneath it, nervously, as we climbed a set of creaking stairs. Upstairs, more squalor was spread before us: an echoing chasm of a room, with a gaping hole where there used to be a bay window.


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It was here—a hundred years ago, when it was a library—where Baron Nopcsa sat and read about dinosaurs, learning the nuances of their bones, theorizing about why the fossils he was finding on the grounds outside were so strange. This castle was Nopcsa’s home, the seat of his family’s dynasty for centuries. Many generations of Nopcsas lived here, and when the baron himself was at the height of his achievement—when he was spying on the Albanians for his empire and lecturing about dinosaurs to packed audiences all over the continent—it probably seemed that many generations more would follow. So, too, it was with the dinosaurs. Toward the end of the Cretaceous—when T. rex and Triceratops were fighting in North America, carcharodontosaurs were hunting gigantic sauropods throughout the south, and a parade of dwarfs had colonized the European islands—dinosaurs seemed invincible. But like castles, like empires, and like genius noblemen with a flair for the dramatic, the great dynasties of evolution can also fall—sometimes when least expected.


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The Rise and Fall of the Dinosaurs 8 Dinosaurs Take Flight Archaeopteryx Chapter Title art by Todd Marshall THERE IS A DINOSAUR OUTSIDE my window. I’m watching it as I write this. Not a photo on a billboard, or a copy of a skeleton from a museum, or one of those obnoxious animatronic things you see in amusement parks. A real, honest-to-goodness, living, breathing, moving dinosaur. A descendant of those plucky dinosauromorphs that emerged on Pangea 250 million years ago, part of the same family tree as Brontosaurus and Triceratops, and a cousin of T. rex and Velociraptor. It’s about the size of a house cat, but with long arms tucked against its chest, and a much shorter pair of twiggy legs. Most of its body is the crisp white of a bridal gown, but the edges of its arms are gray, and the tips of its hands are jet black. As it stands stiff-legged on my neighbor’s rooftop, its head arching proudly upward, it cuts a regal profile against the darkening clouds of eastern Scotland. When the sun breaks through for a moment, I catch a glint reflecting from its beady eyes, which start to dart back and forth. No doubt this is a creature of keen senses and high intelligence, and it’s onto something. Maybe it can tell that I’m watching. Then, without warning, it yawns open its mouth and emits a high-pitched screech—an alarm to its compatriots, perhaps, or a mating call. Or maybe a threat directed my way. Whatever it is, I can hear it clearly through the double glazing, thankful now that there is a pane of glass between us. The fluffy-coated critter becomes silent again and swivels its neck so that it’s now staring directly at me. It definitely knows I’m here. Expecting another shriek, I’m surprised when it closes its mouth, its jaws coming together to form a sharp, yellow beak, which hooks downward at the front. It doesn’t have any teeth, but this beak looks like a nasty weapon that could do a lot of damage. Mindful again that I’m indoors and safe from any harm, I give the glass a playful little tap. And then the creature makes its move. With a grace that I can only struggle to describe, it pushes its webbed feet off the slate tiles, extends its feathered arms outward, and leaps into the breeze. I lose sight of it as it disappears over the trees, probably on its way to the North Sea. THE DINOSAUR I’M watching is a seagull. There are thousands of them living around Edinburgh. I see them every day, sometimes diving for fish in the sea a couple of miles north of my house, but more often I watch in disgust as they pick at discarded burger wrappers and other waste on the streets of the Old Town.


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Occasionally I catch one of them dive-bombing an unsuspecting tourist, spearing a french fry or two with its beak before launching back into the sky. When I observe this type of behavior—the cunning, the agility, the nastiness—it’s easy to see the inner Velociraptor in an otherwise forgettable seagull. Seagulls, and all other birds, evolved from dinosaurs. That makes them dinosaurs. Put another way, birds can trace their heritage back to the common ancestor of dinosaurs, and therefore are every bit as dinosaurian as T. rex, Brontosaurus, or Triceratops, the same way my cousins and I are Brusattes because we trace our lineage back to the same grandfather. Birds are simply a subgroup of dinosaurs, just like the tyrannosaurs or the sauropods—one of the many branches on the dinosaur family tree. It’s a notion that’s so important, it bears repeating. Birds are dinosaurs. Yes, it can be hard to get your head around. I often get people who try to argue with me: sure, birds might have evolved from dinosaurs, they say, but they are so different from T. rex, Brontosaurus, and the other familiar dinosaurs that we shouldn’t classify them in the same group. They’re small, they have feathers, they can fly—we shouldn’t call them dinosaurs. On the face of it, that may seem like a reasonable argument. But I always have a quick retort up my sleeve. Bats look and behave a whole lot differently than mice or foxes or elephants, but nobody would argue that they’re not mammals. No, bats are just a weird type of mammal that evolved wings and developed the ability to fly. Birds are just a weird group of dinosaurs that did the same thing. And just so there is no confusion, I’m talking about birds—real, true birds. This has nothing to do with another favorite cast member of the Age of Dinosaurs, the pterosaurs. Often referred to as pterodactyls, these were reptiles that glided and soared through the air on long, skinny wings anchored by a stretched fourth finger (the ring finger). Most were about the size of average birds today, but some had wingspans wider than small airplanes. They originated around the same time as dinosaurs in the Pangean days of the Triassic, and died out with most dinosaurs at the end of the Cretaceous, but they were not dinosaurs, and they were not birds. Instead, they were close cousins of dinosaurs. Pterosaurs were the first group of vertebrates (animals with backbones) to evolve wings and fly. Dinosaurs—in the guise of birds—were the second. This means that dinosaurs are still among us today. We’re so used to saying that dinosaurs are extinct, but in reality, over ten thousand species of dinosaurs remain, as integral parts of modern ecosystems, sometimes as our food and our pets, and in the case of seagulls, sometimes as pests.


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Indeed, the vast majority of dinosaurs died 66 million years ago, when that latest Cretaceous world of T. rex versus Triceratops, of the giant Brazilian sauropods and Transylvanian island dwarfs, was plunged into chaos. The reign of the dinosaurs ended and a revolution followed, forcing them to cede their kingdom to other species. But a few stragglers made it through, a few dinosaurs that had what it took to endure. The descendants of these remarkable survivors live on today as birds, the enduring legacy of over 150 million years of dinosaur domination, of a dead empire. THE REALIZATION THAT birds are dinosaurs is probably the single most important fact ever discovered by dinosaur paleontologists. Although we’ve learned much about dinosaurs over the past few decades, this is not a radical new idea pushed by my generation of scientists. Quite the opposite: it’s a theory that goes back a long way, to the era of Charles Darwin. The year was 1859. After two decades of sitting around and stewing over the observations he made as a young man sailing the world on the HMS Beagle, Darwin was finally ready to go public with his startling discovery: species are not fixed entities; they evolve over time. He even had a mechanism to explain evolution, a process he called natural selection. That November, he laid it all out in the Origin of Species. This is how it works. All populations of organisms are variable in their features. For instance, if you look at a bunch of rabbits in nature, they will have slightly different fur colors, even if they all belong to the same species. Sometimes one of those variations confers a survival advantage—say, darker fur that helps a rabbit camouflage itself better—and because of that, the individuals with that feature have a better chance of living longer and reproducing more. If that variation is heritable—if it can be passed on to offspring—then over time it will cascade throughout the population so that the entire rabbit species is now dark-haired. Dark hair has been naturally selected, and the rabbits have evolved. This process can even produce new species: if a population is somehow divided and each subset goes its own way, evolving its own naturally selected features until the two subsets are so different that they’re unable to reproduce with each other, they have developed into separate species. This process has brought into being all of the world’s species over the course of billions of years. It means that all living things—modern and extinct—are related, cousins on one grand family tree. Elegant in its simplicity, so far-reaching in its implications, today we regard Darwin’s theory of evolution by natural selection as one of the fundamental rules underpinning the world as we know it.


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It’s what produced the dinosaurs, what molded them into such a fantastic variety of species that were able to rule the planet for so long, adapting to drifting continents, shifting sea levels, changes in temperature, and the threats from competitors hoping to snatch their crown. Evolution by natural selection is also what produced us, and don’t be mistaken, it continues to operate right now, constantly, all around us. It’s why we’re so worried about superbugs that evolve resistance to antibiotics, why we’re always in need of new medicines to stay a step ahead of the bacteria and viruses that will do us harm. Some folks still dispute the reality of evolution today—and I won’t say any more about that—but whatever disagreements we have now pale in comparison to what was happening in the 1860s. Darwin’s book—written in beautiful, accessible prose for public consumption—sparked a fury. Some of society’s most cherished notions about religion, spirituality, and humankind’s place in the universe suddenly seemed up for debate. Evidence and accusations flew back and forth, and both sides were on the lookout for a trump card. For many of Darwin’s supporters, the ultimate proof of his new theory would be “missing links,” transitional fossils that capture, like a freeze frame, the evolution of one type of animal into another. These would not only demonstrate evolution in action, but could visually convey it to the public in a way that no book or lecture ever could. Darwin didn’t have to wait long. In 1861, quarry workers in Bavaria found something peculiar. They were mining a type of fine limestone that breaks into thin sheets, which was used at the time for lithographic printing. One of the miners—now nameless to history—split open a slab and found a 150-million-year-old skeleton of a Frankenstein creature inside. It had sharp claws and a long tail like a reptile but feathers and wings like a bird. Other fossils of the same animal were soon found in other limestone quarries that sprinkled the Bavarian countryside, including a spectacular one that preserved nearly the entire skeleton. This one had a wishbone, like a bird, but its jaws were lined with sharp teeth, like a reptile. Whatever this creature was, it seemed to be half reptile, half bird. This Jurassic hybrid was named Archaeopteryx, and it became a sensation. Darwin included it in later editions of the Origin of Species as evidence that birds had a deep history which could be explained only by evolution. The strange fossil also caught the eye of one of Darwin’s best friends and most vociferous supporters. Thomas Henry Huxley is perhaps best remembered as the man who came up with the term agnosticism to describe his uncertain religious views, but in the 1860s he was popularly known as Darwin’s Bulldog. It was a nickname he gave himself, because he was unrelenting in his defense of Darwin’s theory, taking on anyone—in person or in print—who maligned it.


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Huxley agreed that Archaeopteryx was a transitional fossil, linking reptiles and birds, but he went one step further. He noticed that it bore an uncanny resemblance to another fossil discovered in the same lithographic limestone beds in Bavaria, a small flesh-eating dinosaur called Compsognathus. So he proposed his own radical new idea: birds descended from dinosaurs. Debate continued for the next century. Some scientists followed Huxley; others didn’t accept the link between dinosaurs and birds. Even as a deluge of new dinosaur fossils emerged from the American West—the Jurassic Morrison dinosaurs like Allosaurus and its many sauropod compatriots, the Cretaceous Hell Creek congregation of T. rex and Triceratops—there didn’t seem to be enough evidence to settle the question. Then, in the 1920s, a book by a Danish artist made the simplistic argument that birds couldn’t have come from dinosaurs because dinosaurs apparently didn’t have collarbones (which birds fuse into wishbones), and although it may sound a little absurd, that viewpoint held sway until the 1960s (and today we realize that dinosaurs did indeed have collarbones, so the point is moot). As Beatlemania swept the globe, protesters marched for civil rights in the American South, and war raged in Vietnam, the consensus was that dinosaurs had nothing to do with birds. They were just very distant cousins that looked kind of similar. The feather-covered skeleton of Archaeopteryx, the oldest bird in the fossil record. Photo courtesy of the author That all changed in 1969, that tumultuous year of Woodstock. Revolution was afoot, as societal norms and traditions were being challenged throughout the West. That spirit of rebellion also percolated into science, and paleontologists started to see dinosaurs differently. Not as the dim-witted, dull-colored, slow-moving wastes of space that defined a pointless era of prehistory, but as more active, dynamic, energetic animals that ruled their world through talent and ingenuity, creatures that were very similar in many ways to living animals—particularly birds. A new generation—led by an unassuming Yale professor named John Ostrom and his rambunctious student Robert Bakker—completely reimagined dinosaurs, even making the argument that dinosaurs lived together in herds, had keen senses, cared for their young, and may have been warm-blooded like us. The dromaeosaur (raptor) Velociraptor locked in combat with the primitive horned dinosaur Protoceratops, from the Gobi Desert of Mongolia. Photograph by Mick Ellison, with assistance from Denis Finnin. Photo courtesy of the author The catalyst for this so-called Dinosaur Renaissance was a series of fossils unearthed a few years before, in the mid-1960s, by Ostrom and his team. They were out in far southern Montana, close to the border with Wyoming, prospecting in colorful rocks formed on a floodplain during the Early Cretaceous, some time between 125 and 100 million years ago. They found over a thousand bones of a dinosaur—a dinosaur that was astonishingly birdlike. It had long arms that looked almost like wings and the lithe build indicative of a fast-running dynamo of an animal.


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After a few years of studying the bones, Ostrom announced them in 1969 as a new species: Deinonychus, a raptor. It was a close cousin of Velociraptor, which was discovered in the 1920s in Mongolia and described by Henry Fairfield Osborn (the New York aristocrat who named T. rex), but in these pre–Jurassic Park times, it had yet to become a household name. Ostrom realized the enormous implications of his find. He used Deinonychus to resurrect Huxley’s idea that birds evolved from dinosaurs, which he argued in a series of landmark scientific papers in the 1970s, a lawyer making his case by meticulous presentation of incontrovertible evidence. Meanwhile, his flamboyant former student Bakker went a different route. The cowboy-hatted, hippie-haired child of the Sixties became an evangelist. He preached the dinosaur-bird connection—and the new image of dinosaurs as warm-blooded, big-brained evolutionary success stories—to the public with a Scientific American cover story in 1975 and a wildly successful book in the 1980s, The Dinosaur Heresies. Their contrasting styles caused considerable friction between them, but together Ostrom and Bakker revolutionized how everyone viewed dinosaurs. By the end of the 1980s, most serious students of paleontology had come around to their way of thinking. The recognition that birds came from dinosaurs raised a provocative question. Maybe, Ostrom and Bakker surmised, some of the most familiar features of modern birds first evolved in dinosaurs. Perhaps raptors like Deinonychus—so birdy in their bones and body proportions—even had that one thing that is most quintessentially “bird”: feathers. After all, because birds evolved from dinosaurs, and because the half-dinosaur half-bird Archaeopteryx was found covered in fossilized feathers, feathers must have developed somewhere along their evolutionary lineage—maybe in a dinosaur long before birds came onto the scene. Moreover, if some dinosaurs did have feathers, that would be the final jab in the gut to the few old-blood holdovers who didn’t accept the connection between dinosaurs and birds. The problem, though, is that Ostrom and Bakker couldn’t be sure if dinosaurs like Deinonychus had feathers. All they had were bones. Soft bits like skin, muscles, tendons, internal organs, and yes, feathers, rarely survive the ravages of death, decay, and burial to become fossilized. Archaeopteyx—which Ostrom and Bakker considered the oldest bird in the fossil record—was a lucky exception, having been buried quickly in a quiet lagoon and rapidly turned to stone. Maybe they would never be able to tell one way or another. So they waited, hopeful that somebody, somewhere, somehow would find feathers on a dinosaur. Then in 1996, as his career was drawing to a close, Ostrom was at the annual meeting of the Society of Vertebrate Paleontology in New York, where fossil hunters from around the world congregate to present new discoveries and discuss their research. While milling about the American Museum, Ostrom was approached by Phil Currie, a Canadian who was part of that first post-1960s generation raised on the idea that birds are dinosaurs.


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The theory so fascinated Currie that he spent much of the 1980s and 1990s hunting for small birdlike raptors in western Canada, Mongolia, and China. He had, in fact, just returned from one of his trips to China. While he was there, he caught wind of an extraordinary fossil. He took a photograph of it out of his pocket and showed it to Ostrom. There it was, a small dinosaur surrounded by a halo of feathery fluff, immaculately preserved as if it had died yesterday. Ostrom began to cry. His knees got weak, and he almost fell to the floor. Somebody had found his feathered dinosaur. The fossil Currie showed Ostrom—later named Sinosauropteryx—was only the start. Scientists sprinted to the Liaoning region of northeastern China, where it was found, with the mad ambition of prospectors on a gold rush. But the true authorities were the local farmers. They knew the land intimately and understood that even a single prime specimen, when sold to a museum, could bring them more money than a lifetime of toiling in the fields. Within a few years, farmers from all over the countryside had reported several other feathered dinosaur species, which were given names like Caudipteryx, Protarchaeopteryx, Beipiaosaurus, and Microraptor. Today, some two decades later, more than twenty such species are known, and these are represented by thousands of individual fossils. These dinosaurs had the great misfortune to live in a dense forest surrounding a wonderland of ancient lakes, a landscape that was periodically obliterated by volcanoes. Some of these eruptions spewed out tsunamis of ash, which combined with water to flood the landscape in a viscous ooze that buried everything in sight. The dinosaurs were captured going about their everyday business, preserved Pompeii-style. That’s why the details of the feathers are so pristine. Ostrom was a guy who waited hours for a bus, only to have five come along at once. He now had a whole ecosystem of feathered dinosaurs, which proved him right: birds really did arise from dinosaurs, an extension of the same family as T. rex and Velociraptor. The feathered dinosaurs of Liaoning are now among the most celebrated fossils in the world, and rightly so. When it comes to new dinosaur discoveries, nothing in my lifetime approaches their significance. ONE OF THE greatest privileges I’ve had in my career is studying many of the feathered dinosaurs of Liaoning, in museums all over China. I’ve even had the chance to name and describe a new one, the raptor Zhenyuanlong that we met back in the first few pages of this book, that mule-size creature with wings. These Liaoning dinosaurs are gorgeous fossils—as suited for an art gallery as a natural history museum—but they’re so much more than that. They are the fossils that help us untangle one of the biggest riddles of biology: how evolution produces radically new groups of organisms, with restyled bodies capable of remarkable new behaviors.


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The formation of small, fast-growing, warm-blooded, flying birds from ancestors that looked like T. rex and Allosaurus is a prime example of this sort of jump—what biologists call a major evolutionary transition. You need fossils to study major transitions, because they’re not the sort of thing we can re-create in the lab or witness in nature. The Liaoning dinosaurs are an almost perfect case study. There are a lot of them, and they exhibit great diversity of body size, shape, and feather structure. They run the gamut from dog-size plant-eating ceratopsians with simple porcupine-style quills, to thirty-foot-long primitive cousins of T. rex coated in hairlike fuzz (like Yutyrannus, which we also met a few chapters ago), to raptors like Zhenyuanlong with full-on wings, and even to crow-size weirdos with wings on both the arms and the legs, something not seen in any modern birds. Each is a snapshot, and when stitched together and placed on a family tree, they provide something of a running film of an evolutionary transition in action. Most fundamentally, the Liaoning fossils confirm where birds perch on the dinosaur family tree. Birds are a type of theropod; they are rooted in that group of ferocious meat-eaters that most famously includes T. rex and Velociraptor and also many of the other predators that we’ve come across: the herd-living Coelophysis from Ghost Ranch, the Butcher Allosaurus from the Morrison Formation, the carcharodontosaurs and abelisaurids that terrorized the southern continents. This is exactly what Huxley, and later Ostrom, proposed. The Liaoning fossils sealed the deal by verifying how many features are shared uniquely by birds and other theropods: not just feathers, but also wishbones, three-fingered hands that can fold against the body, and hundreds of other aspects of the skeleton. There are no other groups of animals—living or extinct—that share these things with birds or theropods: this must mean that birds came from theropods. Any other conclusion requires a whole lot of special pleading. Among theropods, birds nest within an advanced group called the paravians. These carnivores break some of the stereotypes that many people still hold about dinosaurs, particularly theropods. They weren’t lumbering monsters like T. rex, but smaller, nimbler, smarter species, most of which were human-size or tinier. In effect, they were a subgroup of theropods that went on their own path, trading the brawn and girth of their ancestors for bigger brains, keener senses, and more compact, lightweight skeletons that permitted a more active lifestyle. Other paravians include Ostrom’s Deinonychus, Velociraptor, and my oh-so-birdlike Zhenyuanlong, along with all of the other dromaeosaurid raptor and troodontid species. These dinosaurs are the closest relatives of birds. They all had feathers, many of them had wings, and more than a few surely looked and acted like modern birds. LEFT The feathered dromaeosaur (raptor) Sinornithosaurus from Liaoning, China. Photograph by Mick Ellison. RIGHT Close-ups of the simple filament-like feathers along the head (top) and longer, quill-type feathers along the forearm (bottom) of Sinornithosaurus. Photograph by Mick Ellison.


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Somewhere within this flock of paravian species lies the line between non-bird and bird. As with the division between non-dinosaur and dinosaur, way back in the Triassic, this distinction is blurry. And it’s getting less distinct with each new fossil from Liaoning. Truthfully, it’s just a matter of semantics: today’s paleontologists define a bird as anything that falls into the group that includes Huxley’s Archaeopteryx, modern birds, and all descendants of their Jurassic common ancestor. It’s more historical convention than a reflection of any biological distinction. By this definition, Deinonychus and Zhenyuanlong fall ever so slightly on the non-bird side of the border. Let’s forget about that for a second. Definitions can distract from the story line. Today’s birds stand out among all modern animals. Feathers, wings, toothless beaks, wishbones, big heads that bob along on an S-shaped neck, hollow bones, toothpick legs . . . the list goes on. These signature features define what we call the bird body plan: the blueprint that makes a bird a bird. This body plan is behind the many superskills that birds are so renowned for: their ability to fly, their hypercharged growth rates, their warm-blooded physiology, and their high intelligence and sharp senses. We want to know where this body plan came from. The feathered dinosaurs of Liaoning give us the answer. And it’s remarkable: many of the supposedly signature features of today’s birds—the components of their blueprint—first evolved in their dinosaur ancestors. Far from being unique to birds, these features developed much earlier, in ground-living theropods, for reasons wholly unrelated to flight. Feathers are the best example—and we’ll return to them in a moment—but they are merely emblematic of a much bigger pattern. To see it, we have to start at the base of the family tree and move up. Let’s begin with a central feature of the bird blueprint. Long, straight legs and feet with three skinny main toes—hallmarks of the modern bird silhouette—first appeared more than 230 million years ago in the most primitive dinosaurs, as their bodies were reshaped into upright-walking, fast-running engines that could outpace and outhunt their rivals. In fact, these hind-limb features are some of the defining characteristics of all dinosaurs, the very things that helped them rule the world for so long. Then a little bit later, some of these upright-walking dinosaurs—the earliest members of the theropod dynasty—fused their left and right collarbones into a new structure, the wishbone. It was a seemingly minor change, which stabilized the shoulder girdle and probably allowed these stealthy, dog-size predators to better absorb the shock forces of grabbing prey. Much later, birds would co-opt the wishbone to serve as a spring that stores energy when they flap their wings. These proto-theropods, however, never could have known this would eventually happen, just as the inventor of the propeller had no idea the Wright Brothers would later put it on an airplane.


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Many tens of millions of years down the line, a subset of these upright-walking, wishbone-chested theropods called maniraptorans developed a gracefully curved neck, for reasons unknown. I speculate it may have had something to do with scouting for prey. Meanwhile, some of these species were getting smaller in size, probably because their shrinking physiques gave them entry to new ecological niches—trees, brush, perhaps even underground caves or burrows that were inaccessible to giants like Brontosaurus and Stegosaurus. Later, a subset of these small, upright, wishboned, bobbing-necked theropods started to fold their arms against the body, probably to protect the delicate quill-pen feathers that were evolving around the same time. These were the paravians—a subgroup of the maniraptorans, and the immediate ancestors of birds. These are just a few examples; there are many more. The point is, when I look at that seagull outside my window, many of the features that allow me to immediately recognize it as a bird are not actually trademarks of birds. They’re attributes of dinosaurs. This pattern isn’t confined to anatomy, either. Many of the most notable behaviors and biological characteristics of living birds also have deep dinosaurian heritage. Some of the best evidence comes not from Liaoning but from another trove of spectacular fossils, found in the Gobi Desert of Mongolia. For the last quarter century, a joint team from the American Museum of Natural History and the Mongolian Academy of Sciences has been mounting annual summer expeditions to this desolate expanse of central Asia. The fossils they have collected—which date from the Late Cretaceous, between about 84 and 66 million years ago—provide unprecedented insight into the lifestyles of dinosaurs and early birds. Leading the Gobi project is one of America’s most prominent paleontologists, Mark Norell, the head of the American Museum’s dinosaur collection and my former PhD supervisor. Mark grew up in Southern California, a long-haired surfer dude who worshipped Jimmy Page but at the same time had a nerdy obsession with collecting fossils. He did his graduate work at Yale, where Ostrom was one of his mentors, and was barely into his thirties when he was hired to Barnum Brown’s old curatorial post, widely regarded as the top dinosaur research job in the world. Mark Norell using one of his signature tricks for collecting fossils in damp conditions: drenching the plaster jacket covering the fossil in gasoline and lighting it on fire. Aino Tuomola. An oviraptor buried while protecting its nest, collected by Mark Norell in Mongolia. Photo courtesy of the author The total opposite of a stuffy academic caricature, Mark travels the planet hunting for the two things he knows best: dinosaurs, obviously, but also his other infatuation: Asian art. The stories he’s accumulated along the way—in auction houses, Chinese dance clubs, Mongolian yurts, fancy European hotels, and seedy bars—often seem too outrageous to be true but make him one of the best raconteurs I’ve known.


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A few years ago, the Wall Street Journal published a hagiography of Mark, referring to him as “the coolest dude alive.” Mark does dress like a hipster version of Andy Warhol (another of his heroes), hold court in a majestic office overlooking Central Park, boast a collection of ancient Buddhist art that puts many museums to shame, and bring portable fridges into the desert so he can make sushi while doing fieldwork. Is it enough to qualify as the single coolest individual in the world? I’ll let others judge. I do know that Mark is one of the world’s best advisors. He’s whip smart and thinks big, always urging his students to ask fundamental questions about how evolution works—for instance, how did a dinosaur turn into a bird? Never a micromanager or a credit stealer, he tries to attract motivated students, supplies them with kick-ass fossils, and then steps aside. That, and he never lets his students pay for beer. I and many of Mark’s students have built our careers studying dinosaurs he wrested from the Gobi. Among them are skeletons entombed by flash storms that captured parent dinosaurs brooding their nests of eggs just like the birds we know today. They show that birds inherited their superb parenting skills from their dinosaurian antecedents, and that these behaviors go back at least to some of the small, winged, arch-necked maniraptoran species. Mark’s crews have also discovered a wealth of dinosaur skulls, including the well-preserved crania of Velociraptor and other maniraptorans. CAT scanning of these specimens—spearheaded by Mark’s former student Amy Balanoff, who we met a couple of chapters ago—has revealed that these dinosaurs had huge brains, with an expanded forebrain at the front. It is the large forebrain that makes modern birds so intelligent and acts as their in-flight computer, allowing them to control the complicated business of flying and navigating the complex 3-D world of the air. We don’t precisely know why these maniraptorans evolved such intelligence, but the Gobi fossils tell us that the ancestors of birds got smart before they took to the skies. The list continues. Numerous theropods, found in the Gobi and elsewhere, had bones hollowed out by air sacs, which, as we learned earlier, are telltale signs that they had the ultra-efficient “flow through” lung that takes in oxygen during both inhalation and exhalation, a precious feature of birds that delivers the juice needed to maintain their high-energy way of life. The microscopic structure of dinosaur bones indicates that many species—including all known theropods—had growth rates and physiologies intermediate between slow-maturing, cold-blooded reptiles and the fast-growing, warm-blooded birds of today. Thus, we now know that a flow-through lung and relatively fast growth emerged more than 100 million years before birds took wing, as those first fast-running, long-legged dinosaurs were carving out a new livelihood as energetic live wires so different from the sluggish amphibians, lizards, and crocodiles they were battling.


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We even know that both the typical sleeping posture of birds and the way in which they mine calcium from their bones for the shells of their eggs first arose in dinosaurs long before birds. What we think of as the bird body plan, therefore, wasn’t so much a fixed blueprint as a Lego set that was put together brick by brick over evolutionary time. The same was true of the classic behavioral, physiological, and biological repertoire of today’s birds. And the same was true of feathers. WHENEVER I VISIT China, I always make time to see Xu Xing. He’s a polite, mild-tempered man who grew up poor in Xinjiang, a politically disputed sweep of western China that was once crossed by the Silk Road. Unlike most children in the West, Xu had no interest in dinosaurs when he was young. He didn’t even know they existed. When he won a prestigious scholarship to go to college in Beijing, the government told him that he would study paleontology, a subject he had never heard of before. Xu complied and actually enjoyed it, and then he went on to train further under Mark Norell in New York. Today, he’s the world’s greatest dinosaur hunter. He’s named more than fifty new species, more than anybody else alive. Compared to Mark’s presidential suite in the turret of the American Museum of Natural History, Xu’s office at the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing is spartan. But it contains some of the most amazing fossils you’ll ever see. In addition to the dinosaurs that Xu finds himself, he is routinely sent bones that have been collected by farmers, construction workers, and various other people from all over China. Many of those are new feather-covered dinosaurs from Liaoning. Whenever I visit and stride up to Xu’s door, I feel the adrenaline of a kid running into a toy store. The fossils I’ve seen in Xu’s office tell the story of how feathers evolved. More than any other part of a bird’s body or biology, feathers are central to figuring out where birds—and many of their unique abilities, like flight—came from. Feathers are nature’s ultimate Swiss Army knife, multipurpose tools that can be used for display, insulation, protection for eggs and babies, and of course, flight. Indeed, they have so many uses that it has been difficult to figure out which purpose they first evolved to serve and how they were modified into airfoils, but the Liaoning fossils are starting to provide an answer. Feathers didn’t suddenly spring forth when the first birds entered the scene; they evolved in their distant dinosaurian ancestors. The common ancestor of all dinosaurs may have even been a feathered species.


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We don’t know for sure, because we can’t study that ancestor directly, but it’s an inference based on an observation: so many small dinosaurs from Liaoning that are well preserved—the bounty of meat-eating theropods like Sinosauropteryx but also pint-size plant-eaters like Psittacosaurus—are found coated in some type of integument. Either these various dinosaurs evolved their feathers separately, which is unlikely, or they inherited them from a deep ancestor. These earliest feathers, however, looked very different from the quill pens of modern birds. The material that glazed the body of Sinosauropteryx and most other Liaoning dinosaurs was more like fluff, made up of thousands of hairlike filaments that paleontologists call proto-feathers. No way could these dinosaurs fly—their feathers were too simple, and they didn’t even have wings. So the first feathers must have evolved for something else, probably to keep these small, chinchilla-like dinosaurs warm or maybe as a way to camouflage their bodies. For most dinosaurs—the vast majority of those that I’ve studied in Xu’s office and in other Chinese museums—a coat of fluffy or bristly feathers was enough. However, in one subgroup—those wishboned, swan-necked maniraptorans—the hairy strands became longer and then started to branch, first into a few simple tufts and then later into a much more orderly system of barbs projecting sideways from a central shaft. Thus, the quill was born (or, in scientist-speak, the pennaceous feather). Lined up and layered across each other on the arms, these more complex feathers formed wings. Many theropods, particularly paravians, had wings of varying shapes and sizes. Some, like the dromaeosaurid Microraptor—one of the first feathered dinosaurs that Xu named and described—even had wings on both the arms and the legs, something unheard of in today’s birds. Wings, of course, are essential for flight. They are the airfoils that provide lift and thrust. For this reason, it was long assumed that wings must have evolved specifically for flight, that some maniraptorans turned their primitive dino-fuzz into sheets of pennaceous quill pens because they were fine-tuning their bodies into airplanes. It’s an intuitive explanation, but it’s probably false. In 2008, a team of Canadian researchers was prospecting the badlands of southern Alberta, an area rich in fossils of tyrannosaurs, ceratopsians, duckbills, and other last-surviving Late Cretaceous dinosaurs of North America. At the helm was another polite, even-tempered scientist: Darla Zelenitsky, one of the world’s experts on dinosaur eggs and reproduction. Her crew had found the skeleton of a horse-size ornithomimosaur—a beaked, omnivorous ostrich-mimic theropod—and its body was surrounded by wispy dark streaks, some of which seemed to continue straight onto the bone. If they were in Liaoning, Darla told her team with a snide laugh, they could call these things feathers and announce the find as a career-defining discovery. But they couldn’t be feathers. This ornithomimosaur was entombed in a sandstone dumped by a river, not rapidly buried in mint condition by Liaoning-style volcanic surges. Plus, no feathered dinosaurs had ever been reported from North America before.


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Darla Zelenitsky collecting dinosaurs in Mongolia. Photo courtesy of the author The joke ran its course a year later, when Darla and her team—which also included her husband François Therrien, an expert on dinosaur ecology—found a nearly identical fossil. Another ornithomimosaur, in sandstone, with a mange of cotton-candy fuzz around it. Something strange was going on, so the duo went into the storehouse of the Royal Tyrrell Museum of Palaeontology, where François is a curator, to check out other ornithomimosaurs in the collection. There they found a third fluffy skeleton that had been discovered in 1995—a year before Phil Currie took that photograph of the first feathered theropod from Liaoning and showed it to John Ostrom. The paleontologists who excavated the Albertan fossil in the mid-1990s didn’t yet know that dinosaur feathers could be preserved, but Darla and François could tell that the tufts on the three ornithomimosaurs were nearly identical in size, shape, structure, and position to the feathers on many of the Liaoning theropods. This could mean only one thing: they had found the first feathered dinosaurs in North America. The ornithomimosaurs that Darla and François discovered didn’t merely have feathers. They also had wings. You can clearly see the black splotches on the arm bones where large, quill-pen-style feathers were anchored, a tidy series of dots and dashes arrayed in lines all up and down the forearm. There’s no way this dinosaur could fly, though—it was far too big and heavy, and its arms were far too short and its wings too small to provide a large enough surface area to support the animal in the air. Moreover, it didn’t have the huge chest muscles necessary to power flight (the breast muscles of today’s birds, whose massive sizes make them good eating) nor the asymmetrical feathers (with a leading vane shorter and stiffer than the trailing vane) that are necessary to withstand the severe forces of surging through an airstream. The same turns out to be true of many of the winged theropods of Liaoning, including Zhenyuanlong. They had wings, sure, but their hefty bodies, pathetically undersize wings, and puny frames made them wholly unsuitable for the air. But why else would a dinosaur develop wings? It may seem like a conundrum, but we have to remember that today’s birds use their wings for many things other than flying (which is why, for instance, flightless birds like ostriches don’t lose their arms entirely). They are also used as display structures to entice mates and frighten rivals, as stabilizers that help birds climb, as fins to help them swim, and as blankets for keeping eggs warm in the nest, along with many other functions. Wings could have evolved for any of these reasons—or maybe another function entirely—but display seems the most likely, and there is growing evidence for it.


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When I was doing my PhD with Mark Norell in New York, there was another student working on his degree a couple of hours north at Yale, in the same department that Ostrom taught in before his death in 2005. Jakob Vinther comes from Denmark, and he has the Viking physique to prove it; he’s tall, with sandy blond hair, a big bushy beard, and intense Nordic eyes. Jakob never intended to study dinosaurs—he yearns for the Cambrian Period, that time a few hundred million years before the dinosaurs when life in the oceans was undergoing its big bang. While studying these ancient animals, Jakob started to wonder about how fossil preservation works on the microscopic scale. He began to look at lots of different fossils under high-powered microscopes and realized that many of them preserved a variety of small, bubblelike structures. Comparisons to modern animal tissues showed these to be melanosomes: pigment-bearing vessels. Because melanosomes of different size and shape correspond to different colors—sausage-shaped ones make black; meatball-shaped ones, a rusty red; and so on—Jakob gathered that by looking at fossilized melanosomes, you could tell what colors prehistoric animals would have been when they were alive. We were always told this was impossible, but Jakob proved the experts wrong. In my mind, it’s one of the cleverest things a paleontologist has ever done in my lifetime. Naturally, Jakob decided to take a gander at the newly discovered feathered dinosaurs. If the feathers were preserved well enough, he hoped, they might contain melanosomes. One by one, Jakob and his colleagues in China put the Liaoning dinosaurs under the microscope, and his hunch was proven correct. They found melanosomes everywhere—of all shapes and sizes, orientations, and distributions—which reveal that the feathers of nonflying, winged dinosaurs were a rainbow of different colors. Some were even iridescent, like those of today’s shiny-sheened crows. Colorful wings like these would have been perfect display instruments—just like the fabulous tail of a peacock. Although it doesn’t definitively prove that these dinosaurs were using their wings for display, it is solid circumstantial evidence. The totality of the evidence—that wings first evolved in dinosaurs too large and ungainly to fly, that these wings were ornately colored, and that modern birds use their wings for display—has led to a radical new hypothesis. Wings originally evolved as display structures—as advertising billboards projecting from the arms, and in some cases, like Microraptor, the legs, and even the tail. Then these fashionably winged dinosaurs would have found themselves with big broad surfaces that by the unbreakable laws of physics could produce lift and drag and thrust. The earliest winged dinosaurs, like the horse-size ornithomimosaurs and even most raptors like Zhenyuanlong, probably would have considered the lift and drag produced by their billboards to be little more than an annoyance. In any case, whatever lift was generated wasn’t nearly enough to get such large animals into the air.


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But in more advanced paravians, which had the magic combination of bigger wings and smaller body size, the billboards would have been able to take on an aerodynamic function. These dinosaurs could now move around in the air, even if awkwardly at first. Flight had evolved—and it had happened totally by accident, the billboards now repurposed as airfoils. The more fossils we find—particularly in Liaoning—the more complex the story gets. The early development of flight appears to have been chaotic. There was no orderly progression, no long evolutionary march in which one subgroup of dinosaurs was refined into ever better aeronauts. Instead, evolution had produced a general type of dinosaur—small, feathered, winged, fast-growing, efficient-breathing—that had all of the attributes needed to start playing around in the air. There seems to have been a zone on the dinosaur family tree where this type of animal had free reign to experiment. Flight probably evolved many times in parallel, as different species of these dinosaurs—with their different airfoil and feather arrangements—found themselves generating lift from their wings as they leaped from the ground, scurried up trees, or jumped between branches. Some of them were gliders, able only to soar passively on air currents. Microraptor undoubtedly could glide, as its arm and leg wings were big enough to support its body in the air. This isn’t just conjecture but has been demonstrated by experiments in which scientists have built anatomically correct, life-size models and stuck them in wind tunnels. Not only do they submissively stay afloat, but they’re pretty good at coasting in the airflow. There’s also another type of dinosaur that could probably glide, but in a much different way than Microraptor. The tiny Yi qi—maybe the wackiest dinosaur ever found—had a wing, but not made of feathers. Instead, it had a membrane of skin stretching between its fingers and body, like a bat. This membrane must have been a flight structure, but it was not flexible enough to actively flap, so gliding is really the only possibility. The fact that Microraptor and Yi have such divergent wing configurations is some of the strongest evidence that different dinosaurs were evolving distinct flight styles independently of one another. Other feathered dinosaurs would have started flying in a different way—by flapping. This is called powered flight, because the animal actively generates lift and thrust by beating its wings. Mathematical models suggest that some non-bird dinosaurs were plausible flappers, including Microraptor and the troodontid Anchiornis, as both had wings big enough and a body light enough that flapping could have powered them through the air, at least theoretically. These first attempts probably would have been awkward, as these dinosaurs wouldn’t have had the muscle strength or stamina to stay in the sky very long, but they provided evolution with a starting point. Now, with these big-winged, small-bodied dinosaurs fluttering around, natural selection could get to work and modify these creatures into better fliers.


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One of these wing-beating lineages—maybe the descendants of Microraptor or Anchiornis, or one that evolved completely separately—got even smaller, developed bigger chest muscles and hyperelongated arms. They lost their tails and teeth, ditched one of their ovaries, and hollowed out their bones even more to lessen their weight. Their breathing became more efficient, their growth faster, and their metabolism more supercharged, so that they became fully warm-blooded, able to maintain a constant high internal body temperature. With each evolutionary enhancement, they became even better fliers, some able to stay airborne for hours on end, others able to sail through the oxygen-starved upper reaches of the troposphere, over the rising Himalayas. These were the dinosaurs that became the birds of today. EVOLUTION MADE BIRDS from dinosaurs. And as we’ve seen, it happened slowly, as one lineage of theropod dinosaurs acquired the characteristic features and behaviors of today’s birds piecemeal, over tens of millions of years. A T. rex didn’t just mutate into a chicken one day, but rather, the transition was so gradual that dinosaurs and birds just seem blend into each other on the family tree. Velociraptor, Deinonychus, and Zhenyuanlong are on that “non-bird” side of the genealogy, but were they around today, we would probably consider them just another type of bird, no stranger than a turkey or an ostrich. They had feathers, they had wings, they guarded their nests and cared for their babies, and hell, some of them could probably even fly a little bit. During the tens of millions of years that dinosaurs were evolving the signature features of birds one by one, there was no long game, no greater aim. There was no force guiding evolution to make these dinosaurs ever more adapted to the skies. Evolution works only in the moment, naturally selecting features and behaviors that make an animal successful in its particular time and place. Flight was something that just kind of happened when the time was right. It may have even gotten to the point where it was inevitable. If evolution manufactures a small, long-armed, big-brained hunter with feathers to keep warm and wings to woo mates, it doesn’t take very much for that animal to start flapping around in the air. In that moment, working with a fluttering dinosaur with some awkward aerial ability struggling to survive in a dinosaur-eat-dinosaur world, natural selection could kick in and start shaping its progeny into even better fliers. With each additional refinement, you would have something that could fly better, farther, faster—until a modern-style bird had emerged. The culmination of this long transition was a game-changer in the history of life. When evolution had finally succeeded in assembling a small, winged, flying dinosaur, a great new potential was unlocked. These first birds began to diversify like crazy, probably because they had evolved a new ability that allowed them to invade novel habitats and live a different lifestyle than their predecessors. We can see this (relatively) sudden change in the fossil record.


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As part of my PhD project, I joined forces with two number crunchers to assess how rates of evolution changed across the dinosaur-bird transition. Graeme Lloyd and Steve Wang are paleontologists, but I don’t know if either of them has ever collected a fossil. They are first-rate statisticians—math whizzes who take joy in sitting in front of their computers for hours, writing code and running analyses. The three of us worked together to devise a new way of calculating how fast or slow animals change features of their skeletons over time and how these rates change branch by branch on the family tree. We started with the big new genealogy of birds and their closest theropod cousins that I produced with Mark Norell. We then made a vast database of anatomical features that vary in these animals—some species, for example, have teeth, but others, a beak. By mapping the distribution of these characteristics onto the family tree, we could see where one condition changed into another, where teeth gave way to beaks, and so on. This allowed us to count up how many changes occurred on each branch of the tree. We could also figure out how much time each branch on the tree represented, by using the ages of each fossil. Change over time is rate, and thus we could measure the pace of evolution for each branch. Then, using Graeme and Steve’s statistical know-how, we could test whether certain time intervals in dinosaur-bird evolution, or certain groups on the family tree, had higher rates of change than others. The results were about as clear as anything I’ve ever seen spit out of a statistics software program: most theropods were evolving at ho-hum background rates, but then, once an airworthy bird had emerged, the rates went into overdrive. The first birds were evolving much faster than their dinosaur ancestors and cousins, and they maintained these accelerated rates for many tens of millions of years. Meanwhile, other studies have shown that there was a sudden decrease in body size and a spike in rates of limb evolution right around this same point on the genealogy, as these first birds were quickly getting smaller and growing longer arms and bigger wings so that they could fly better. Although it had taken tens of millions of years for evolution to make a flying bird out of a dinosaur, now things were happening very fast, and birds were soaring. A QUICK WALK from Xu Xing’s office in Beijing is another room, brighter and less solemn but with fewer fossils. It’s where Jingmai O’Connor works—but only part of the time. The reason there aren’t many fossils here is because Jingmai studies Liaoning birds—the bona fide fliers that flapped over the heads of the feathered dinosaurs—and most of these are crushed onto limestone slabs, so she can describe and measure them from photographs blown up on her computer screen.


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That means she can easily work from home, which is deep among the last remaining Beijing hutongs—traditional narrow-alleyed neighborhoods of single-story stone buildings pasted together. Good thing too, because she spends a lot of her nonscience time hanging about in the hutongs, raving and even occasionally DJ-ing in the trendy clubs of China’s suddenly hip capital. Jingmai calls herself a paleontologista—fitting, given her fashionista style of leopard-print Lycra, piercings, and tattoos, all of which are at home in the club but stand out (in a good way) among the plaid-and-beard crowd that dominates academia. A native of Southern California—half Irish, half Chinese by blood—Jingmai is a Roman candle of energy—delivering caustic one-liners one moment, speaking in eloquent paragraphs about politics the next, and then it’s on to music or art or her own unique personal brand of Buddhist philosophy. Oh yes, and she’s also the world’s number one expert on those first birds that broke the bounds of Earth to fly above their dinosaur ancestors. Many birds lived during the Age of Dinosaurs. The first flapping fliers must have originated sometime before 150 million years ago, because that is the age of Archaeopteryx, Huxley’s Frankenstein creature, which is still, as far as we know, the very oldest true bird, unarguably capable of powered flight, in the fossil record. Most likely, evolution had already assembled a small, winged, flapping, bona fide bird sometime in the middle part of the Jurassic Period, around 170 to 160 million years ago. That means there was a good hundred million years during which birds coexisted with their dinosaur predecessors. LEFT Yanornis, a species of true bird—which could fly by flapping its large feathered wings—from Liaoning, China. RIGHT Jingmai O’Connor, the world’s leading expert on the oldest bird fossils. Photo courtesy of the author A hundred million years is a lot of time to attain a lot of diversity, particularly as these early birds were evolving at such fast rates compared to other dinosaurs. The Liaoning birds that Jingmai studies are a snapshot of this Mesozoic aviary—the best portrait of what birds were doing during the earliest years of their evolutionary history. Every week, middlemen and museum curators from all over China send photographs to Jingmai and her colleagues in Beijing, of new bird fossils plucked from the rolling fields of northeastern China by farmers. Thousands of these fossils have been reported over the last two decades, and they are much more common than feathered dinosaurs like Microraptor and Zhenyuanlong. It’s probably because flocks of primitive birds were suffocated by noxious gases from the big volcanic eruptions, and their limp bodies then fell into the lakes and forests that were buried by the ashy sludge that also entombed the feathered dinosaurs. Week after week, Jingmai opens her e-mail, downloads the photographs, and finds herself staring at a new type of bird. These birds include countless species; Jingmai seems to be naming a new one every month or two.


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They lived in the trees, on the ground, and even in and around the water like ducks. Some of these still had teeth and long tails, retained from their Velociraptor-like forebears, whereas others had the tiny bodies, huge breast muscles, stubby tails, and majestic wings of modern birds. Meanwhile, gliding and gawkily flapping alongside these birds were some of those other dinosaurs experimenting with flight—the four-winged Microraptor, the bat-winged species, and so on. This is more or less where things stood 66 million years ago. This whole suite of birds and other airborne dinosaurs was there, gliding and flapping overhead, when T. rex and Triceratops were duking it out in North America, carcharodontosaurs were chasing titanosaurs south of the equator, and dwarf dinosaurs were hopping across the islands of Europe. And then they witnessed what came next, the instant that snuffed out almost all of the dinosaurs, all but a few of the most advanced, best-adapted, best-flying birds, which made it through the carnage and are still with us today—among them the seagulls outside my window.


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The Rise and Fall of the Dinosaurs 9 Dinosaurs Die Out Edmontosaurus Chapter Title art by Todd Marshall IT WAS THE WORST DAY in the history of our planet. A few hours of unimaginable violence that undid more than 150 million years of evolution and set life on a new course. T. rex was there to witness it. When a pack of Rexes woke up that morning 66 million years ago on what would go down as the final day of the Cretaceous Period, all seemed normal in their Hell Creek kingdom, the same as it had for generations, for millions of years. Forests of conifers and ginkgos stretched to the horizon, interspersed with the bright flowers of palms and magnolias. The distant churn of a river, rushing eastward to empty into the great seaway that lapped against western North America, was drowned out by the low bellow of a herd of Triceratops several thousand strong. As the pack of T. rex readied themselves for the hunt, sunlight began to trickle through the forest canopy. It highlighted the outlines of various small critters darting through the sky, some flapping their feathered wings and others gliding on currents of hot air rising from the humidity of the young day. Their chirps and tweets were beautiful, a dawn symphony that could be heard by all the other creatures of the forest and floodplains: armored ankylosaurs and dome-headed pachycephalosaurs hiding in the trees, legions of duckbills just beginning their breakfast of flowers and leaves, raptors chasing mouse-size mammals and lizards through the brush. Then things started to get weird, truly outside all norms of Earth history. For the last several weeks, the more perceptive of the Rexes may have noticed a glowing orb in the sky, far off in the distance—a hazy ball with a fiery rim, like a duller and smaller version of the sun. The orb seemed to be getting larger, but then it would disappear from view for large portions of the day. The Rexes wouldn’t have known what to make of it; it was far beyond their brainpower to contemplate the motions of the heavens. But this morning, as the pack broke through the trees and emerged onto the riverbank, all of them could see that something was different. The orb was back, and it was gigantic, its shine illuminating much of the sky to the southeast in a cloudy psychedelic mist. Then, a flash. No noise, only a split-second flare of yellow that lit up the whole sky, disorienting the Rexes for a moment. As they blinked their eyes back to focus, they noticed that the orb was now gone, the sky a dull blue. The alpha male turned to check on the rest of his pack . . . . And then they were blindsided. Another flash, but this one far more vengeful. The rays lit the morning air in a fireworks display and burned into their retinas.


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One of the juvenile males fell over, cracking his ribs. The rest of them stood frozen, blinking manically, trying to rid themselves of the sparks and speckles that flooded their vision. Still no sound to go with the visual fury. In fact, no noise at all. By now, the birds and flying raptors had stopped chirping, and silence hung over Hell Creek. The calm lasted for only a few seconds. Next, the ground beneath their feet started to rumble, then to shake, and then to flow. Like waves. Pulses of energy were shooting through the rocks and soil, the ground rising and falling, as if a giant snake were slithering underneath. Everything not rooted into the dirt was thrown upward; then it crashed down, and then up and down again, the Earth’s surface having turned into a trampoline. Small dinosaurs and the little mammals and lizards were catapulted upward, then splattered onto trees and rocks when they landed. The victims danced across the sky like shooting stars. Even the largest, heaviest, forty-foot-long Rexes in the pack were launched several feet off the ground. For a few minutes, they bounced around helplessly, flailing about as they rode the trampoline. Moments earlier they had been the undisputed despots of an entire continent; now they were little more than seven-ton pinballs, their limp bodies careening and colliding through the air. The forces were more than enough to crush skulls, snap necks, and break legs. When the shaking finally stopped and the ground was no longer elastic, most of the Rexes were littered along the riverbank, casualties on a battlefield. Very few of the Rexes—or the other dinosaurs of Hell Creek—were able to walk away from the bloodbath. But some did. As the lucky survivors staggered out, sidestepping the corpses of their compatriots, the sky began to change color above them. Blue turned to orange, then to pale red. The red got sharper and darker. Brighter, brighter, brighter. As if the headlights of a giant oncoming car were coming closer and closer. Soon everything was bathed in an incandescent glory. Then the rains came. But what fell from the sky was not water. It was beads of glass and chunks of rock, each one scalding hot. The pea-size morsels pelted the surviving dinosaurs, gouging deep burns into their flesh. Many of them were gunned down, and their shredded corpses joined the earthquake victims on the battlefield. Meanwhile, as the bullets of glassy rock whizzed down from above, they were transferring heat to the air. The atmosphere grew hotter, until the surface of the Earth became an oven. Forests spontaneously ignited and wildfires swept across the land. The surviving animals were now roasting, their skin and bones cooking at temperatures that instantaneously produce third-degree burns. It was no more than fifteen minutes since the T. rex pack was startled by that first jolt of light, but by now they were all dead, as were most of the dinosaurs they had lived with.


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The once-lush woodlands and river valleys were aflame. Still, animals had survived—some of the mammals and lizards were underground, some of the crocodiles and turtles were underwater, and some of the birds had been able to fly to safer refuges. Over the next hour or so, the rain of bullets ceased, and the air cooled. A breath of calm once again settled over Hell Creek. It seemed that the danger was over, and many of the survivors came out of their hiding places to survey the scene. Carnage everywhere, and although the sky was no longer radioactive red, it was getting blacker as it choked up with soot from the forest fires, which were still raging. As a couple of raptors sniffed the charred bodies of the T. rex pack, they must have thought that they had survived the apocalypse. They were wrong. Some two and a half hours after the first light flash, the clouds began to howl. The soot in the atmosphere began to swirl into tornadoes. And then—woosh—the wind charged across the plains and through the river valleys, blowing at hurricane force, hard enough to make many of the rivers and lakes burst their banks. Along with the wind was a deafening noise, louder than anything these dinosaurs had ever heard. Then another. Sound travels much slower than light, and these were the sonic booms that occurred at the same time as the two light flashes, caused by the distant horror that had started the chain reaction of brimstone hours earlier. The raptors shrieked in pain as their ears ruptured, and many of the smaller critters hurried back into the safety of their burrows. While all of this was happening in western North America, other parts of the world were going through their own upheavals. The earthquakes, glassy-rock rain, and hurricane winds were less severe in South America, where carcharodontosaurs and giant sauropods roamed. The same was true of the European islands that the weird Romanian dwarf dinosaurs called home. Still, these dinosaurs also had to deal with quaking ground, wildfires, and intense heat, and many of them died during those same chaotic two hours that wiped out most of the Hell Creek community. Other places, though, had it much worse. Much of the mid-Atlantic coast was sliced apart by tsunamis twice as tall as the Empire State Building, which flushed the carcasses of plesiosaurs and other sea-dwelling giant reptiles far inland. Volcanoes started to spew out rivers of lava in India. And a zone of Central America and southern North America—everything within a radius of about six hundred miles (one thousand kilometers) of the Yucatán Peninsula of modern-day Mexico—was annihilated. Vaporized. As the morning gave way to afternoon and then evening, the winds died down. The atmosphere continued to cool, and although there were a few aftershocks, the ground was stable and solid. The wildfires seared away in the background.


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When night finally came and this most horrible of days finally was over, many—maybe even most—of the dinosaurs were dead, all over the world. Some did stagger on, however, into the next day, the next week, the next month, the next year, and the next decades. It was not an easy time. For several years after that terrible day, the Earth turned cold and dark because soot and rock dust lingered in the atmosphere and blocked out the sun. The darkness brought cold—a nuclear winter that only the hardiest of animals could survive. The darkness also made it very difficult for plants to subsist, as they need sunlight to power photosynthesis to make their food. As plants died, food chains collapsed like a house of cards, killing off many of the animals that had been able to endure the cold. Something similar happened in the oceans, where the death of photosynthesizing plankton took out the larger plankton and fish that fed on them and in turn the giant reptiles at the top of the food pyramid. The sun did eventually break through the darkness, as the soot and other gunk was leached out of the atmosphere by rainwater. These rains, however, were highly acidic and would have scalded much of the Earth’s surface. And the rain was not able to remove some ten trillion tons of carbon dioxide that had been blown up into the sky with the soot. CO2 is a nasty greenhouse gas that traps heat in the atmosphere, and soon nuclear winter gave way to global warming. All of these things conspired in a war of attrition to knock off whatever dinosaurs were not felled by the initial cocktail of earthquakes, brimstone, and fires. A few hundred years after that dreadful day—a few thousand years at the absolute most—western North America was a scarred, post-apocalyptic landscape. What was once a diverse ecosystem of sweeping forests, alive with the hoofbeats of Triceratops and ruled by T. rex, was now quiet and mostly empty. Here and there, the odd lizard scurried through the bushes, some crocodiles and turtles paddled in the rivers, and rat-size mammals periodically peeked out of their burrows. A few birds were still around, picking at seeds still buried in the soil, but all the other dinosaurs were gone. Hell Creek had turned to Hell. So had much of the rest of the world. It was the end of the Age of Dinosaurs. WHAT HAPPENED ON that day—when the Cretaceous ended with a bang and the dinosaurs’ death warrant was signed—was a catastrophe of unimaginable scale that, thankfully, humankind has never experienced. A comet or an asteroid—we aren’t sure which—collided with the Earth, hitting what is now the Yucatán Peninsula of Mexico. It was about six miles (ten kilometers) wide, or about the size of Mount Everest. It was probably moving at a speed of around 67,000 miles per hour (108,000 kilometers per hour), more than a hundred times faster than a jet airliner.


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When it slammed into our planet, it hit with the force of over 100 trillion tons of TNT, somewhere in the vicinity of a billion nuclear bombs’ worth of energy. It plowed some twenty-five miles (forty kilometers) through the crust and into the mantle, leaving a crater that was over 100 miles (160 kilometers) wide. The impact made an atom bomb look like a Fourth of July cherry bomb. It was a bad time to be alive. The Hell Creek dinosaurs were living about 2,200 miles (3,500 kilometers) northwest of ground zero, as the Microraptor flies. Give or take a little artistic license, they would have experienced the string of terrors described above. Their cousins in New Mexico—southern versions of T. rex, other types of horned and duck-billed dinosaurs, and some of the few sauropods living in North America, whose bones I’ve collected during many summers of fieldwork—would have been even worse off. They were only about 1,500 miles (2,400 kilometers) from the impact site. The closer you were, the greater the horrors: the light and sound pulses would have arrived quicker, the earthquakes would have been more severe, the rain of glass and rocks would have been heavier, and the temperature of the oven would have been greater. All creatures living within six hundred miles (a thousand kilometers) or so of the Yucatán would have been instantly turned into ghosts. Earth forty-five seconds after the impact of the Chicxulub asteroid, with a growing cloud of dust and molten rock shooting into the atmosphere and a fire-igniting heat pulse starting to spread across the oceans and land. Artwork by Donald E. Davis, NASA. Relief map of the modern-day Yucatán Peninsula of Mexico, showing the outline of the Chicxulub crater (the remainder of the crater is underwater). Courtesy of NASA. The glowing orb in the sky, which piqued the interest of the T. rex herd, was the comet or asteroid itself (from here on out, I’ll just refer to it as an asteroid for simplicity). If you were around back then, you would have seen it. The experience would have probably been similar to those times Halley’s Comet has come close to Earth. Seemingly floating up in the heavens, the asteroid would have appeared harmless. You would have been oblivious, at least at first. The first flash of light occurred as the asteroid punched through the Earth’s atmosphere and violently compressed the air in front of it, so much that the air became four or five times as hot as the surface of the sun and ignited. The second flash was the impact itself, when asteroid met bedrock. The sonic booms associated with both of these flashes followed many hours later, sound moving much slower than light. With them came the winds, which probably blasted at over 600 miles per hour (1,000 kilometers per hour) close to the Yucatán and still at several hundred miles per hour by the time they reached Hell Creek.


The rise and fall of the dinosaurs [eBook - NC Digital -- Steve Brusatte -- 1, 2018 -- William Morrow -- 9780062490421 -- 819b642fffa68675f9e07cf3af773125 -- Anna’s Archive.6

(For comparison, Hurricane Katrina’s maximum wind speed was measured at about 175 miles per hour.) As the asteroid and Earth smashed together, an enormous amount of energy was unleashed, which fed shock waves that caused the ground to shake like a trampoline. These earthquakes were probably around 10 on the Richter scale—far more powerful than anything human civilizations have ever coped with. Some of these earthquakes triggered the Atlantic tsunamis, which ripped up house-size boulders and flung them far inland; others kicked the Indian volcanoes into hyperdrive, and they kept erupting for thousands of years, compounding everything else the asteroid had wrought. The energy from the collision vaporized the asteroid and the bedrock that it hit. Dust, dirt, rock, and other debris from the collision shot up into the sky—most as vapor or liquid but some as small but still solid pieces of rock. Some of this material flew past the outer fringes of the atmosphere into outer space. But what goes up (as long as it doesn’t reach escape velocity) must come down, and as it did, the liquified rock cooled into glassy blobs and tear-shaped spears, which transferred heat to the atmosphere, transforming it into an oven. The spiking temperatures lit forests on fire—maybe not all over the world, but certainly in much of North America and anywhere else within a few thousand miles of the Yucatán. We see the singed remnants of leaves and wood—the kind of stuff left after a campfire has been extinguished—in rocks that were laid down right after the asteroid hit. The soot from the fires, with other dust and grime kicked up by the impact but too light to fall back down to earth, would have floated up into the atmosphere, clogging the currents that circulate air across the globe, until the entire planet was dark. The ensuing period—thought to be equivalent to a global nuclear winter—probably killed off most of the dinosaurs in areas far from the smoldering crater. I could go on and on, exhausting my thesaurus, but if I go much further, you probably won’t believe me. Which would be a shame, because all that I write really happened. And we know that because of the work of one man, a geological genius who is one of my scientific heroes: Walter Alvarez. WE’VE ALREADY ESTABLISHED that I did some silly things in high school, when my obsession with dinosaurs overtook my better judgment. My fanboy stalking of Paul Sereno wasn’t nearly the worst of it. Nothing was more brazen than when I picked up the phone one day in the spring of 1999 and cold-called Walter Alvarez at his office in Berkeley, California. I was a fifteen-year-old kid with a rock collection; he was the eminent National Academy of Sciences member who nearly twenty years earlier had proposed the idea that a giant asteroid impact killed off the dinosaurs. He answered on the second ring.


The rise and fall of the dinosaurs [eBook - NC Digital -- Steve Brusatte -- 1, 2018 -- William Morrow -- 9780062490421 -- 819b642fffa68675f9e07cf3af773125 -- Anna’s Archive.7

Even more astounding, he didn’t hang up as I rambled on about the purpose of my call. I had read his book T. rex and the Crater of Doom—still, to my mind, one of the best pop-science books on paleontology ever written—and was captivated by how he put together the clues that pointed to the asteroid. His book explained how the detective game started in a rocky gorge on the outskirts of the medieval commune of Gubbio, in the Apennine Mountains of Italy. It was here where Alvarez first noticed the unusual character of the thin band of clay that marked the end of the Cretaceous. As chance had it, my family was gearing up for a trip to Italy to celebrate my parents’ twentieth wedding anniversary. It would be my first time outside of North America, and I wanted to make it memorable. For me, that wasn’t basilicas and art museums, but a pilgrimage to Gubbio, to stand on the spot where Alvarez started to figure out one of the biggest riddles in science. But I needed directions, so I decided to go straight to the source. Professor Alvarez gave me detailed instruction that even a kid without any modicum of Italian could follow. We also talked for a while about my interest in science. Looking back, I am astonished that such a scientific giant could be as kind and generous with his time as he was. But alas, it turned out to be for naught, because my family never made it to Gubbio that summer. Floods closed the main rail line from Rome, and I was devastated. My whining nearly ruined my parents’ second honeymoon. Five years later, however, I was back in Italy for a college geology field course. We were staying in a small observatory in the Apennines run by Alessandro Montanari, one of the many scientists who made a name in the 1980s studying the end-Cretaceous extinction. On our first-day tour we passed through the library, where a solitary figure was scrutinizing a geological map under a flickering light. “I want you all to meet my friend and mentor, Walter Alvarez,” Sandro said in his singsong Italian accent. “Some of you may have heard of him.” I was paralyzed. Never, before or since, have I been as gobsmacked. The rest of the tour was a blur, but afterward I sneaked back to the library and gently opened the door. Alvarez was still there, hunched over the map in a trance of concentration. I felt bad about interrupting him—maybe he was homing in on some other unsolved mystery of Earth history. I introduced myself and was gobsmacked a second time when he remembered our conversations from a few years back. “Did you make it to Gubbio back then?” he asked me. I could only mutter an embarrassed no, not really wanting to admit that I had wasted his time with that phone call—and several e-mails that followed.