The Best American Science and Nature Writing 2020

by Michio Kaku

  I got in, and we drove for an hour or so, turning through a ranch gate and following a maze of bone-rattling roads that eventually petered out in a grassy basin. The scattered badlands of Hell Creek form an otherworldly landscape. This is far-flung ranching and farming country; prairies and sunflower fields stretch to the horizon, domed by the great blue skies of the American West. Roads connect small towns—​truck stop, church, motel, houses and trailers—​and lonely expanses roll by in between. Here and there in the countryside, abandoned farmhouses lean into the ground. Over millions of years, the Hell Creek layer has been heavily eroded, leaving only remnants, which jut from the prairie like so many rotten teeth. These lifeless buttes and pinnacles are striped in beige, chocolate, yellow, maroon, russet, gray, and white. Fossils, worked loose by wind and rain, spill down the sides.

  When we arrived, DePalma’s site lay open in front of us: a desolate hump of gray, cracked earth, about the size of two soccer fields. It looked as if a piece of the moon had dropped there. One side of the deposit was cut through by a sandy wash, or dry streambed; the other ended in a low escarpment. The dig was a three-foot-deep rectangular hole, sixty feet long by forty feet wide. A couple of two-by-fours, along with various digging tools and some metal pipe for taking core samples, leaned against the far side of the hole. As we strolled around the site, I noticed on DePalma’s belt a long fixed-blade knife and a sheathed bayonet—​a Second World War relic that his uncle gave him when he was twelve, he said.

  He recalled the moment of discovery. The first fossil he removed, earlier that summer, was a five-foot-long freshwater paddlefish. Paddlefish still live today; they have a long bony snout, with which they probe murky water in search of food. When DePalma took out the fossil, he found underneath it a tooth from a mosasaur, a giant carnivorous marine reptile. He wondered how a freshwater fish and a marine reptile could have ended up in the same place, on a riverbank at least several miles inland from the nearest sea. (At the time, a shallow body of water, called the Western Interior Seaway, ran from the proto-Gulf of Mexico up through part of North America.) The next day, he found a two-foot-wide tail from another marine fish; it looked as if it had been violently ripped from the fish’s body. “If the fish is dead for any length of time, those tails decay and fall apart,” DePalma said. But this one was perfectly intact, “so I knew that it was transported at the time of death or around then.” Like the mosasaur tooth, it had somehow ended up miles inland from the sea of its origin. “When I found that, I thought, There’s no way, this can’t be right,” DePalma said. The discoveries hinted at an extraordinary conclusion that he wasn’t quite ready to accept. “I was 98 percent convinced at that point,” he said.

  The following day, DePalma noticed a small disturbance preserved in the sediment. About three inches in diameter, it appeared to be a crater formed by an object that had fallen from the sky and plunked down in mud. Similar formations, caused by hailstones hitting a muddy surface, had been found before in the fossil record. As DePalma shaved back the layers to make a cross-section of the crater, he found the thing itself—​not a hailstone but a small white sphere—​at the bottom of the crater. It was a tektite, about three millimeters in diameter—​the fallout from an ancient asteroid impact. As he continued excavating, he found another crater with a tektite at the bottom, and another, and another. Glass turns to clay over millions of years, and these tektites were now clay, but some still had glassy cores. The microtektites he had found earlier might have been carried there by water, but these had been trapped where they fell—​on what, DePalma believed, must have been the very day of the disaster.

  “When I saw that, I knew this wasn’t just any flood deposit,” DePalma said. “We weren’t just near the KT boundary—​this whole site is the KT boundary!” From surveying and mapping the layers, DePalma hypothesized that a massive inland surge of water flooded a river valley and filled the low-lying area where we now stood, perhaps as a result of the KT-impact tsunami, which had roared across the proto-Gulf and up the Western Interior Seaway. As the water slowed and became slack, it deposited everything that had been caught up in its travels—​the heaviest material first, up to whatever was floating on the surface. All of it was quickly entombed and preserved in the muck: dying and dead creatures, both marine and freshwater; plants, seeds, tree trunks, roots, cones, pine needles, flowers, and pollen; shells, bones, teeth, and eggs; tektites, shocked minerals, tiny diamonds, iridium-laden dust, ash, charcoal, and amber-smeared wood. As the sediments settled, blobs of glass rained into the mud, the largest first, then finer and finer bits, until grains sifted down like snow.

  “We have the whole KT event preserved in these sediments,” DePalma said. “With this deposit, we can chart what happened the day the Cretaceous died.” No paleontological site remotely like it had ever been found, and, if DePalma’s hypothesis proves correct, the scientific value of the site will be immense. When Walter Alvarez visited the dig last summer, he was astounded. “It is truly a magnificent site,” he wrote to me, adding that it’s “surely one of the best sites ever found for telling just what happened on the day of the impact.”

  * * *

  When DePalma finished showing me the dig, he introduced me to a field assistant, Rudy Pascucci, the director of the Palm Beach Museum. Pascucci, a muscular man in his fifties, was sunburned and unshaven, and wore a sleeveless T-shirt, snakeproof camouflage boots, and a dusty Tilley hat. The two men gathered their tools, got down on the floor of the hole, and began probing the three-foot-high walls of the deposit.

  For rough digging, DePalma likes to use his bayonet and a handheld Marsh pick, popularized by the nineteenth-century Yale paleontologist Othniel C. Marsh, who pioneered dinosaur-hunting in the American West and discovered eighty new species. The pick was given to him by David Burnham, his thesis adviser at Kansas, when he completed his master’s degree. For fine work, DePalma uses X-Acto knives and brushes—​the typical tools of a paleontologist—​as well as dental instruments given to him by his father.

  The deposit consisted of dozens of thin layers of mud and sand. Lower down, it graded into a more turbulent band of sand and gravel, which contained the heavier fish fossils, bones, and bigger tektites. Below that layer was a hard surface of sandstone, the original Cretaceous bedrock of the site, much of which had been scoured smooth by the flood.

  Paleontology is maddening work, its progress typically measured in millimeters. As I watched, DePalma and Pascucci lay on their stomachs under the beating sun, their eyes inches from the dirt wall, and picked away. DePalma poked the tip of an X-Acto into the thin laminations of sediment and loosened one dime-size flake at a time; he’d examine it closely, and, if he saw nothing, flick it away. When the chips accumulated, he gathered them into small piles with a paintbrush; when those piles accumulated, Pascucci swept them into larger piles with a broom and then shoveled them into a heap at the far end of the dig.

  Occasionally, DePalma came across small plant fossils—​flower petals, leaves, seeds, pine needles, and bits of bark. Many of these were mere impressions in the mud, which would crack and peel as soon as they were exposed to the air. He quickly squirted them with PaleoBond, which soaked into the fossils and held them together. Or, using another technique, he mixed a batch of plaster and poured it on the specimen before it fell apart. This would preserve, in plaster, a reverse image of the fossil; the original was too short-lived to be saved.

  When the mosquitoes got bad, DePalma took out a briar pipe and packed it with Royal Cherry Cavendish tobacco. He put a lighter to it and vigorously puffed, wreathing himself in sickly-sweet smoke, then went back to work. “I’m like a shopaholic in a shoe store,” he said. “I want everything!”

  He showed me the impression of a round object about two inches wide. “This is either a flower or an echinoderm,” he said, referring to a group of marine life-forms that includes sea urchins and starfish. “I’ll figure it out in the lab.” He swiftly entombed it in PaleoBond and plaster. Next,
he found a perfect leaf, and near that a seed from a pinecone. “Cretaceous mulch,” he said, dismissively; he already had many similar examples. He found three more small craters with tektites in them, which he sectioned and photographed. Then his X-Acto blade turned up a tiny brown bone—​a jaw, less than a quarter-inch in length. He held it up between his fingers and peered at it with a lens.

  “A mammal,” he said. “This one was already dead when it was buried.” Weeks later, in the lab, he identified the jaw as probably belonging to a mammal distantly related to primates—​including us.

  Half an hour later, DePalma discovered a large feather. “Every day is Christmas out here,” he said. He exposed the feather with precise movements. It was a crisp impression in the layer of mud, perhaps thirteen inches long. “This is my ninth feather,” he said. “The first fossil feathers ever found at Hell Creek. I’m convinced these are dinosaur feathers. I don’t know for sure. But these are primitive feathers, and most are a foot long. There are zero birds that big from Hell Creek with feathers this primitive. It’s more parsimonious to suggest it was a known dinosaur, most likely a theropod, possibly a raptor.” He kept digging. “Maybe we’ll find the raptor that these feathers came from, but I doubt it. These feathers could have floated from a long way off.”

  His X-Acto knife unearthed the edge of a fossilized fin. Another paddlefish came to light; it later proved to be nearly six feet long. DePalma probed the sediment around it, to gauge its position and how best to extract it. As more of it was exposed, we could clearly see that the fish’s two-foot-long snout had broken when it was forced—​probably by the flood’s surge—​against the branches of a submerged araucaria tree. He noted that every fish he’d found in the site had died with its mouth open, which may indicate that the fish had been gasping as they suffocated in the sediment-laden water.

  “Most died in a vertical position in the sediment, didn’t even tip over on their sides,” he said. “And they weren’t scavenged, because whatever would have dug them up afterward was probably gone.” He chipped away around the paddlefish, exposing a fin bone, then a half-dollar-size patch of fossilized skin with the scales perfectly visible. He treated these by saturating them with his own special blend of hardener. Because of the extreme fragility of the fossils, he would take them back to his lab, in Florida, totally encased in sediment, or “matrix.” In the lab, he would free each fossil under a magnifying glass, in precisely controlled conditions, away from the damaging effects of sun, wind, and aridity.

  As DePalma worked around the paddlefish, more of the araucaria branch came to light, including its short, spiky needles. “This tree was alive when it was buried,” he said. Then he noticed a golden blob of amber stuck to the branch. Amber is preserved tree resin and often contains traces of whatever was in the air at the time, trapping the atmospheric chemistry and even, sometimes, insects and small reptiles. “This is Cretaceous flypaper,” he said. “I can’t wait to get this back to the lab.”

  An hour later, he had chiseled all the way around the fish, leaving it encased in matrix, supported by a four-inch-tall pedestal of rock. “I’m pretty sure this is a species new to science,” he said. Because the soft tissue had also fossilized, he said, even the animal’s stomach contents might still be present.

  He straightened up. “Time to plaster,” he said. He took off his shirt and began mixing a five-gallon bucket of plaster with his hands, while Pascucci tore strips of burlap. DePalma took a two-by-four and sawed off two foot-long pieces and placed them like splints on either side of the sediment-encased fossil. One by one, he dipped the burlap strips in the plaster and draped them across the top and the sides of the specimen. He added rope handles and plastered them in. An hour later, when the plaster had cured, he chiseled through the rock pedestal beneath the fossil and flipped the specimen over, leaving the underside exposed. Back in the lab, he would go through this surface to access the fossil, with the plaster jacket acting as a cradle below. Using the rope handles, DePalma and Pascucci lugged the specimen, which weighed perhaps 200 pounds, to the truck and loaded it into the back. Later, DePalma would store it behind a friend’s ranch house, where all his jacketed fossils from the season were laid out in rows, covered with tarps.

  DePalma resumed digging. Gusts of wind stirred up clouds of dust, and rain fell; when the weather cleared, the late-afternoon sun spilled across the prairie. DePalma was lost in another day, in another time. “Here’s a piece of wood with bark-beetle traces,” he said. Plant fossils from the first several million years after the impact show almost no signs of such damage; the insects were mostly gone. The asteroid had likely struck in the fall, DePalma speculated. He had reached this conclusion by comparing the juvenile paddlefish and sturgeon he’d found with the species’ known growth rates and hatching seasons; he’d also found the seeds of conifers, figs, and certain flowers. “When we analyze the pollen and diatomaceous particles, that will narrow it down,” he said.

  In the week that followed, fresh riches emerged: more feathers, leaves, seeds, and amber, along with several other fish, three to five feet long, and a dozen more craters with tektites. I have visited many paleontological sites, but I had never seen so many specimens found so quickly. Most digs are boring; days or weeks may pass with little found. DePalma seemed to make a noteworthy discovery about every half-hour.

  When DePalma first visited the site, he noted, partially embedded on the surface, the hip bone of a dinosaur in the ceratopsian family, of which triceratops is the best-known member. A commercial collector had tried to remove it years earlier; it had been abandoned in place and was crumbling from years of exposure. DePalma initially dismissed it as “trash” and decried the irresponsibility of the collector. Later, though, he wondered how the bone, which was heavy, had arrived there, very close to the high-water mark of the flood. It must have floated, he said, and to have done so it must have been encased in desiccated tissue—​suggesting that at least one dinosaur species was alive at the time of the impact. He later found a suitcase-size piece of fossilized skin from a ceratopsian attached to the hip bone.

  At one point, DePalma set off to photograph the layers of the deposit which had been cut through and exposed by the sandy wash. He scraped smooth a vertical section and misted it with water from a spray bottle to bring out the color. The bottom layer was jumbled; the first rush of water had ripped up layers of mud, gravel, and rocks and tumbled them about with pieces of burned (and burning) wood.

  Then DePalma came to a faint jug-shaped outline in the wall of the wash. He examined it closely. It started as a tunnel at the top of the KT layer, went down, and then widened into a round cavity, filled with soil of a different color, which stopped at the hard sandstone of the undisturbed bedrock layer below. It looked as though a small animal had dug through the mud to create a hideout. “Is that a burrow?” I asked.

  DePalma scraped the area smooth with his bayonet, then sprayed it. “You’re darn right it is,” he said. “And this isn’t the burrow of a small dinosaur. It’s a mammal burrow.” (Burrows have characteristic shapes, depending on the species that inhabit them.) He peered at it, his eyes inches from the rock, probing it with the tip of the bayonet. “Gosh, I think it’s still in there!”

  He planned to remove the entire burrow intact, in a block, and run it through a CT scanner back home, to see what it contained. “Any Cretaceous mammal burrow is incredibly rare,” he said. “But this one is impossible—​it’s dug right through the KT boundary.” Perhaps, he said, the mammal survived the impact and the flood, burrowed into the mud to escape the freezing darkness, then died. “It may have been born in the Cretaceous and died in the Paleocene,” he said. “And to think—​66 million years later, a stinky monkey is digging it up, trying to figure out what happened.” He added, “If it’s a new species, I’ll name it after you.”

  When I left Hell Creek, DePalma pressed me on the need for secrecy: I was to tell no one, not even close friends, about what he’d found. The history o
f paleontology is full of tales of bribery, backstabbing, and double-dealing. In the nineteenth century, Othniel C. Marsh and Edward Drinker Cope, the nation’s two leading paleontologists, engaged in a bitter competition to collect dinosaur fossils in the American West. They raided each other’s quarries, bribed each other’s crews, and vilified each other in print and at scientific meetings. In 1890, the New York Herald began a series of sensational articles about the controversy with the headline “Scientists Wage Bitter Warfare.” The rivalry has since become known as the Bone Wars. The days of skulduggery in paleontology have not passed; DePalma was deeply concerned that the site would be expropriated by a major museum.

  * * *

  DePalma knew that a screwup with this site would probably end his career, and that his status in the field was so uncertain that he needed to fortify the find against potential criticism. He had already experienced harsh judgment when, in 2015, he published a paper on a new species of dinosaur called a Dakotaraptor, and mistakenly inserted a fossil turtle bone in the reconstruction. Although rebuilding a skeleton from thousands of bone fragments that have commingled with those of other species is not easy, DePalma was mortified by the attacks. “I never want to go through that again,” he told me.

  For five years, DePalma continued excavations at the site. He quietly shared his findings with a half-dozen luminaries in the field of KT studies, including Walter Alvarez, and enlisted their help. During the winter months, when not in the field, DePalma prepared and analyzed his specimens, a few at a time, in a colleague’s lab at Florida Atlantic University, in Boca Raton. The lab was a windowless, wedgelike room in the geology building, lined with bubbling aquarium tanks and shelves heaped with books, scientific journals, pieces of coral, mastodon teeth, seashells, and a stack of .50-caliber machine-gun rounds, dating from the Second World War, that the lab’s owner had recovered from the bottom of the Atlantic Ocean. DePalma had carved out a space for himself in a corner, just large enough for him to work on one or two jacketed fossils at a time.