Copyright

William Collins

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This eBook first published in Great Britain by William Collins in 2018

Copyright © 2018 by Smithsonian Institution

Design by Anna Morrison; Illustrations by Alex Boersma

First published in the United States of America by Viking, an imprint of Penguin Random House LLC in 2018 as Spying on Whales: The Past, Present, and Future of Earth’s Most Awesome Creatures

The author asserts the moral right to be identified as the author of this work.

A catalogue record for this book is available from the British Library.

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Source ISBN: 9780008244460

Ebook Edition © June 2018 ISBN: 9780008244484

Version: 2019-04-18

Dedication

Every author writes with a very specific reader in mind.

I wrote this book for you.

And for my family.

Epigraph

What have we been doing all these centuries but trying to call God back to the mountain, or, failing that, raise a peep out of anything that isn’t us? What is the difference between a cathedral and a physics lab? Are not they both saying: Hello? We spy on whales and on interstellar radio objects; we starve ourselves and pray till we’re blue.

—Annie Dillard, Teaching a Stone to Talk

For the animal shall not be measured by man. In a world older and more complete than ours, they move finished and complete, gifted with the extension of the senses we have lost or never attained, living by voices we shall never hear. They are not brethren, they are not underlings: they are other nations, caught with ourselves in the net of life and time, fellow prisoners of the splendour and travail of the earth.

—Henry Beston, The Outermost House

Contents

Cover

Title Page

Copyright

Dedication

Epigraph

Map

Prologue

PART I: PAST

1. How to Know a Whale

2. Mammals Like No Other

3. The Stories Bones Tell

4. Time Travel on the Fossil Whale Highway

5. The Afterlife of a Whale

6. Rock Picks and Lasers

7. Cracking the Case of Cerro Ballena

PART II: PRESENT

8. The Age of Giants

9. The Ocean’s Utmost Bones

10. A Discovery at Hvalfjörður

11. Physics and Flensing Knives

12. The Limits of Living Things

PART III: FUTURE

13. Arctic Time Machines

14. Shifting Baselines

15. All the Ways to Go Extinct

16. Evolution in the Anthropocene

17. Whalebone Junction

Epilogue

A Family Tree of Whales

Notes

Selected Bibliography

Index

Acknowledgments

About the Publisher

Map

At this very moment, two spacecraft move at over thirty-four thousand miles per hour, about ten billon miles away from us, each carrying a gold-plated copper record. The spacecraft, Voyager 1 and Voyager 2, are meant as messengers: they carry information about our address in the solar system, the building blocks of our scientific knowledge, and a small sampling of images, music, and greetings from around the world. They also carry whalesong.

The long squeaks and moans on the record belong to humpback whales. In the 1970s, when the Voyager mission launched, our view of whales was rapidly changing, from game animals to cultural icons and symbols of a nascent environmental movement. Scientists had recently discovered that male humpbacks produce complex songs, composed of phrases collected under broader themes, nested like Russian dolls that repeat in a loop. Humpback whalesong has evolved even since we started listening as each new singer improvises on the loop, creating new structures and hierarchies that constantly change over years, and across ocean basins.

Whalesong, however, remains a riddle to anyone who isn’t a humpback whale. We can capture its variation, details, and complexity, but we don’t know what any of it truly means. We lack the requisite context to decipher and understand it—or, really, any part of cetacean culture. Even so, we send whalesong into interstellar space because the creatures that sing these songs are superlative beings that fill us with awe, terror, and affection. We have hunted them for thousands of years and scratched them into our mythologies and iconography. Their bones frame the archways of medieval castles. They’re so compelling that we imagine aliens might find them interesting—or perhaps understand their otherworldly, ethereal song.

In the meantime, whales here on Earth remain mysterious. They live 99 percent of their lives underwater, far away from continuous contact with people and beyond most of our observational tools. We tend to think about them only when we glimpse them from the safety of a boat, or when they wash up along our shores. They also have an evolutionary past that is surprising and incompletely known. For instance, they haven’t always been in the water. They descend from ancestors that lived on land, more than fifty million years ago. Since then, they transformed from four-limbed riverbank dwellers to oceangoing leviathans, in a chronicle we can read only from their fossil record, a puzzle of bone shards unevenly spread across the globe.

The little we have learned about whales leaves us unsatisfied because the scales of their lives and facts of their bodies are endlessly fascinating. They are the biggest animals on Earth, ever. Some can live more than twice as long as we do. Their migrations take them across entire oceans. Some whales pursue prey with a filter on the roof of their mouth, while others evolved the ability to navigate an abyss with sound. And then they speak to one another with impenetrable languages. All the while, in the short clip of our own history, we’ve moved from heedlessly hunting them to an awareness that they have culture, just as we do, and that our actions, both direct and indirect, put their fate in jeopardy.

A paleontologist is a good tour guide for what we know about whales, not just because their evolutionary history is profoundly interesting. It’s because we, as paleontologists, are used to asking questions without having all of the facts. Sometimes we’re losing facts: fossils removed from their medium lose clues of context; promising bonebeds are razed to make room for roadways; or bones lay misidentified in a museum drawer. When faced with these challenges, paleontologists turn to inference, drawing on many different lines of evidence to understand processes and causes that we cannot directly see or study—the same approach used by any detective, really. In other words, thinking like a detective is a useful approach to confront the mysteries posed by the past, present, and future of whales.

This book is not a synoptic, comprehensive account of every different species of whale—there are far too many whales to fit into anything shorter than an encyclopedia. Instead, this book presents a selective account, a kind of travelogue to chasing whales, both living and extinct. I describe my experiences from Antarctica to the deserts in Chile, to the tropical coastlines of Panama, to the waters off Iceland and Alaska, using a wide variety of devices and tools to study whales: suction-cupped tags that cling to their backs; knives to dissect skin and blubber from muscles and nerves; and hammers to scrape and whack away rock that obscures gleaming, fossilized bone.

The narratives in this book group into three general sections: past, present, and future. Broadly, I want to answer questions about where whales came from, how they live today, and what will happen to them on planet Earth in the age of humans (a new era that some scientists call the Anthropocene). But these stories don’t cleanly fit into these three temporal silos. Instead, they build on one another and reciprocate because the ways that we need to think about whales require thinking about all the evidence at hand: unraveling the many mysteries of living whales requires a background about their evolutionary past, just as much as the surprises from the fossil record can clarify the meaningful facts about their lives today and into the future.

The first part of the book tells the chronicle of how whales went from walking on land to being entirely aquatic, relying on evidence from the fossil record showing what the earliest whales looked like. These fossils show us details that we couldn’t otherwise know about the history of whales, and I explore exactly how we dig up these clues in the first place. Following fossil whale bones brought me to the Atacama Desert of Chile, where my colleagues and I puzzled over an ecological detective story with the discovery of Cerro Ballena, the world’s richest fossil whale graveyard. How did this site come about, and what does it tell us about whales in geologic time?

The second part examines how and why whales became the biggest creatures ever in the history of life. The challenges of studying organisms as large as the largest species of whales means thinking about the limits of biology, and what exactly organisms at these superlative scales need to do, on a daily basis, to sustain their enormous sizes. While trying to connect muscle to bone at a whaling station, I share another serendipitous find: the discovery of an entirely new sensory organ in whales. What does an organ, lodged right at the tip of a whale’s chin, mean for how, when, and why baleen whales evolved to become all-time giants?

Lastly, the third part explores the specter of the uncertain future that we share with whales on Anthropocene Earth. In the twentieth century alone, whaling in the open oceans killed more than three million whales, reducing many populations to shadows of their baseline abundances. Despite this decimation, no single species went extinct until the first decade of the twenty-first century. Since then, not a whistle or splash of the Yangtze river dolphin has been recorded, and responsibility for the extinction of this species can be placed squarely on our shoulders: we dammed the only river in which it lived. Other species, such as the vaquita, remain on the extinction watch list, numbering fewer than one dozen or two dozen individuals. But the news from the field isn’t entirely dire: some whale species have rebounded from the brink, even expanding to new habitats as climate and oceans change. What can we imagine about our shared future with whales, drawing on their lives today and what we know about their evolutionary past?

Ultimately, the quest to understand whales is a human enterprise. This book is a story not just about knowing whales but also about the scientists who study them. The scientists described in these stories come from a variety of different disciplines, ranging from cell biology and acoustics to stratigraphy and parachute physics. Some are historical but very much knowable through their writings, their specimen collections, and the intellectual questions that they asked. One of the great privileges of my professional life is the opportunity to work at the Smithsonian, which has afforded me not only the latitude to undertake this pursuit but also firsthand access to some of the world’s largest and most important collections of material evidence, be it specimens, scientific journals, or unpublished field notes. Every day, I think about the many generations of scientists before me who handled this same evidence, scratching away at the very same questions, while constrained by the circumstances of their times. My hope is that this book says as much about the inner lives of scientists as it does about whales.

I sat transfixed by a sea littered with a million fragments of ice, all rising and falling in time with the slow roll of the waves. We had spent the morning looking for humpback whales in Wilhelmina Bay, threading our rubber boat between gargantuan icebergs that were tall and sharp, like overturned cathedrals. Now we stopped, cut the engine, and listened in the utter stillness for the lush, sonorous breath of an eighty-thousand-pound whale coming to the water’s surface. That sound would be our cue to close in. We had come to the end of the Earth to place a removable tag on the back of one of these massive, oceangoing mammals, but we took nothing for granted in Antarctica. As we sat waiting on the small open boat, I came to feel more and more vulnerable, a speck floating in a sea of shattered ice. “Don’t fall in,” my longtime collaborator and friend Ari Friedlaender deadpanned.

I struggled to remember how long we had been away from the Ortelius, our much larger oceanic vessel with its ice-hardened steel hull. In every direction, we were enclosed by a landscape of nunataks, jagged spires of rock that pierced the creamy tops of surrounding glaciers. Where the glaciers met the sea, they ended in sheer, icy cliffs towering over the bay. Without a human structure for scale, these landforms seemed both near and far at the same time. This otherworldly scene of ice, water, rock, and light warped my sight lines, bending my sense of distance and the passage of time.

If you hold your fist with your left thumb out, your thumb is the western Antarctic Peninsula; your fist, the Antarctic continent’s outline. The Gerlache Strait is part of a long stretch of inner passageway along the outer side of Antarctica’s left thumb, and Wilhelmina Bay cuts a rough cul-de-sac off the Gerlache. The Gerlache is a hot spot for whales, seals, penguins, and other seabirds, and Wilhelmina Bay is the bull’s-eye. All come here to hunt for krill, small crustaceans that form the centerpiece of Antarctic ocean food webs. Consider your hand again: individual krill are about the length of your thumb, but whales pursue them because they explode into great aggregations, or swarms, during the Antarctic summer. With the right mixture of sunlight and nutrient-rich water, dense clouds of krill form a sort of superorganism that can stretch for miles and concentrate in hundreds of individuals per cubic foot. By some measures, there is more biomass of krill than of any other animal on the planet. Calorie-rich swarms of them lurked somewhere, not far, just under our boat.

Where there are krill in sufficient quantities, there will be whales, but the fundamental problem with studying whales is that we almost never see them, except when they come to the surface to breathe or when we dive, in our own limited fashion, in search of them. Whales are inherently enigmatic creatures because the parameters of their lives defy many of our tools to measure them: they travel over spans of whole oceans, dive to depths where light does not reach, and live for human lifetimes—and even longer.

In Wilhelmina Bay our goal was to attach a sleek plastic tag to the back of a whale to record audio, video, depth, changes in the whale’s speed, and even pitch, yaw, and roll. Our tags would provide crucial context for how humpbacks interact with their environment by relaying, in a time-stamped way, how they feed on krill. Ari and his colleagues have tagged and tracked whales along the Antarctic Peninsula for nearly two decades, charting their movements against the backdrop of changes in krill-patch density, water temperature, daylight, and other variables. As climate change warms the poles faster than the rest of the planet, every year counts.

I sat on the gunnel of the boat while Ari scanned from the bow. We were several days into a multiweek expedition with high hopes to tag as many humpbacks as possible—ideally, a pod feeding together—but thus far we had been skunked. Ari stood rigid like a figurehead, holding a twenty-foot-long carbon-fiber pole in folded arms. The pole flexed in synchrony with the swell, the teardrop-shaped tag bobbing at one end. I watched clouds shift slowly overhead, mirroring the dappled quicksilver of the water, and wondered whether any other place on Earth could feel as alien as Antarctica. Then a loud gurgle interrupted my daydreaming, followed by a trumpeting blast of water vapor bursting from flaring, paired nostrils. A whale’s blow.

We knew to expect more plumes of water immediately thereafter. A pod of whales synchronize when they surface to breathe—sometimes nearly simultaneously or split seconds apart. They usually breathe a few times in a row, in quick succession, before resubmerging—unless they’re asleep or truly exhausted, whales tend to act like surfacing is a nuisance and they’d rather be deep underwater. Their tight coordination in breathing likely has a lot to do with maximizing time spent below the surface engaged in the cooperative tasks of finding food and avoiding predators. Some species travel or hunt in pods that are tightly knit family genealogies, while others, such as the humpbacks before us, form short-lived associations, seemingly a matter of happenstance.

“Oh, that’s right,” Ari called out. The vapor from the blow lingered in the cold air. Ari pointed to a small patch of water a dozen yards from the boat, perfectly calm against the waves at the surface. This patch, called a flukeprint, betrayed the whale’s movement, unseen deep below our tiny boat. The single flukeprint bloomed into several, each the size of our boat, rising up from the depths, whirling and spreading into the smooth geometry of a lily pad. We were right. “He’s got buddies,” Ari said. Without the aid of an echo sounder—which would also tip off the whales about our location—we used the ephemeral patterns on the surface to read their path.

We started up the engine, throttling ahead slightly to a spot beyond the last flukeprint. Within seconds, right on cue, a pair of enormous nostrils bubbled at the surface, releasing a thundering tone and then a spray that carried past us as we kept up with the whale. A dorsal fin surfaced, and a second and third blow exploded nearby. “Pull up behind this last one. We have about three more breaths until they go down,” Ari shouted.

We trailed the laggard of the group, maneuvering the boat into position. Ari lowered himself across the bow and held the pole against his torso, extending the tip with the tag just ahead of the dorsal fin as we motored close to the behemoths moving yards away. Then, in a decisive motion, Ari launched the tip of the pole toward the whale’s back, where the tag’s suction cups hit the skin with a satisfying thwack. The whale rolled beneath the surface as we pulled back to pause and wait for it to return. We spotted its sleek, shiny back as it arose again, marked with a neon tag, and we cheered. The whale took one last breath before it raised its monstrously wide tail flukes out of the water and slipped down into emerald darkness with the others. Ari radioed back to the Ortelius. “Taaaaag on,” he said with a hint of swagger as he grinned at me.

Tag on

The whole rodeo of tagging is a bit like sticking a smartphone on the back of a whale, complete with the logistics of getting close enough to a forty-ton mammal in the first place. Just as your smartphone can record movies, track where you go, and automatically rotate images, the same technology—miniaturized and cheap, combining video, GPS, and accelerometers all in one device—has fueled a revolution in understanding how animals move throughout their world. Scientists call this new way of recording organismal movement biologging, and it has captured the interest of ecologists, behavioral biologists, and anatomists, all interested in knowing the details of how animals move through space and over time. Biologging has been especially important for revealing the daily, monthly, and even annual meanderings of animals that are extremely difficult to study. Stick a tag on a penguin, a sea turtle, or a whale, and there’s a chance to know how it swims, what it eats, and everything else it does whenever you’re not around to watch it—which is most of the time, for animals at sea.

The logistics of studying whales places them in a realm truly apart from every other large mammal on land or at sea. To know anything about them in the wild takes time on a boat, sticking a tag on their back, sliding a camera underwater, or spying overhead with a drone—if you’re lucky enough to come upon them in the first place. Biologging is helping us overcome this challenge by giving us a remote view into their lives, an extension of our senses more intimate and sometimes more detailed than any telephoto lens. In the case of humpbacks, tag data have revealed how these gulp-feeding whales lunge at large schools of krill and other prey, oftentimes in coordinated attacks. It’s a form of pack hunting, which might seem strange for a species celebrated as gentle giants. But baleen whales are serious predators, not like grazing cows but more like wolves or lions, pursuing their quarry with strategy and efficacy. Don’t be fooled by their lack of teeth, or just because krill don’t bleat in terror.

Hours later the Ortelius prowled silently through Wilhelmina Bay, with a pair of massive spotlights leading the way in search of icebergs in our path. Outside on the bow, I watched heavy snowflakes drift through the cones of light as Ari unfolded the metal radio antenna that would lead us back to our tag. The tags we were using had to be re-collected to yield their data; we would have to find and physically pluck them out of the water, provided that they’d already been knocked off the whales’ backs. By design, they can last minutes, hours, or even days from the force of suction alone, before being scraped, being bumped, or falling off. Its buoyant neon housing would keep the whole device floating on the surface until we triangulated its position.

Over the course of his career, Ari has probably tagged more species of whales than anyone, in all circumstances and in every ocean. Beyond friendship, mutual colleagues, shared ambitions, and wry humor, we were working together in Antarctica to build a bridge between our disciplines—paleontology for me, ecology for him—because questions about how whales evolved to become masters of ocean ecosystems over fifty-odd million years need to be grounded in the facts of what whales do today. Bridging gaps between disciplines sometimes necessitates spending time side by side. All the better if it’s in the field.

The metal prongs that Ari assembled looked like an elaborate set of rabbit ears from an old television set. He plugged the antenna into a small receiver with a speaker, and after a few moments, we heard a series of intermittent beeps. “That gap between the beeps tells us that the whale is sleeping, rising up to the surface to breathe, and then sinking back down.” Ari smiled. “Just dozing, belly full of krill. Not a bad way to spend a Saturday night.” We would need to come back later and listen again for our tag until it floated freely, beeping uninterrupted.

Most large baleen whale species alive today belong to the rorqual family, which feed on krill and other small prey by lunging underwater. They comprise the more familiar members of the cetacean bestiary, including humpbacks, blue whales, fin whales, and minke whales. Rorquals are also the most massive species of vertebrates ever to have evolved on the planet—far heavier than the largest dinosaurs. Even the smallest rorquals, minke whales, can weigh ten tons as adults, about twice as much as an adult bull African elephant. Rorquals are easy to distinguish from any other baleen whale, such as a gray whale or a bowhead whale: look for the long, corrugated throat pouch that runs from their chin to their belly button. (And yes, whales have belly buttons, just like you and me.) The features that make rorquals so obviously different from other baleen whales also play a critical role in how they feed.

Across whole ocean basins, individual whales find their food using probability, heading for feeding grounds burned into memory from a lifetime of migration. Rorquals travel routes that span hemispheres over the seasons; an individual whale might migrate from the tropics in the winter in search of mates and to bear young, then to the poles during the summer to forage under constant sunlight. Baleen whales still retain olfactory lobes, unlike their toothed cousins, such as killer whales and dolphins, which have lost them. Baleen whales might smell some aspect of their prey at the water’s surface, and it is possible that this mechanism could refine their search once on the scene. Originally their sense of smell evolved for transmission through air, not water; we know little beyond the basics about this sense in whales. Somehow, whales manage to be in the right place at the right time to feed. And what’s clear from biologging is that once in the right place, baleen whales spot the prey patches from below, probably approaching them by sight. Lacking the echolocation of their toothed relatives, vision is likely the dominant sense for baleen whales at short range.

With prey in range, a rorqual accelerates, fluking at top speed, and begins the amazing process of a lunge. Surging from below, it opens its mouth only seconds before it arrives at a patch of krill or school of fish, which may be as big as or bigger than the entire whale. When it lowers its jaws, the rorqual exposes its mouth immediately to a rush of water that pushes its tongue backward, through the floor of its mouth, into its throat pouch. In mere seconds, the accordion-like grooves of its throat pop out like a parachute. After engulfing the prey-laden water, the whale slows, almost to a halt, pouch distended and looking bloated, nothing like its airfoil-shaped profile from moments prior. Over the next minute, it slowly expels water out of its mouth through a sieve of baleen, until its throat pouch returns to its original form, the prey swallowed. For their part, krill and fish deploy collective defensive behavior by dispersing to try to escape the oncoming maw of death. In the end, a successful whale takes a bite out of a much bigger, more diffuse and dynamic superorganism.

Lunge feeding has been described as one of the largest biomechanical events on the planet, and it’s not hard to imagine why when you consider that an adult blue whale engulfs a volume of water the size of a large living room in a matter of seconds. Tags on humpbacks in other parts of Antarctica show how they sometimes feed close to the seafloor in pairs, swimming alongside each other as they scrape the bottom with their protruding chins in mirrored unison. Tags have also shown us that rorquals are right- or left-handed, just like us, favoring either a dextral or sinistral direction when they roll their bodies to feed.

The more scientists tag whales, the more it’s apparent that there’s still much that we don’t know. It turns out that blue whales have a behavior where they spin 360 degrees underwater in a pirouette before they lunge, probably to line up their mouths precisely with a patch of krill. Other lightweight tags, launched with barbs that cling more deeply beneath the skin on the dorsal fin, have tracked the movement of Antarctic minke whales migrating over eight thousand miles of open ocean, from the Antarctic Peninsula to subtropical waters. These tags upload data directly to satellites whenever the whale surfaces, over the course of weeks to months, before eventually falling out. These tags are also especially useful for species that are rarely seen, such as beaked whales. Satellite-linked dive tags deployed on Cuvier’s beaked whales revealed, in a precise way, the astonishing extremes of their foraging dives for squid and fish—over 137.5 minutes of breath holding, 2,992 meters deep—data that set new dive records for a mammal. If the idea of holding your breath for over two hours doesn’t alarm you, imagine doing it while chasing your dinner to a depth of nearly two miles.

Tag data combined with tissue samples taken from biopsy darts tell us that these humpback whales feeding in the western Antarctic Peninsula are merely seasonal visitors for the austral summer. By early fall, they depart the icy bays, cross the great Circum-Antarctic Current that rings the seventh continent, and undertake various paths over thousands of miles to arrive at temperate latitudes. At Wilhelmina Bay the overwhelming majority of humpbacks return to the low latitudes of the Pacific coasts of Costa Rica and Panama to mate and give birth before returning to the Southern Ocean for the next austral summer to feed.

We eventually retrieved the tag, along with its data, and continued to Cuverville Island, on the other side of Wilhelmina Bay. As the Ortelius maneuvered out of the Gerlache and toward the island, I watched from the ship’s stern as we passed icebergs more massive than any I had yet seen. Their fragmented sides, a hundred feet high, were etched in luminous, milky blues and grays. They held light from sea to sky, glowing in unearthly ways, as if they could not have been formed on this planet. And of course they were mostly sheathed underwater, which was a bit of an ominous thought; the Ortelius kept a careful distance. But the incomprehensibility of something as overwhelming as an iceberg is belied by its transience: even the largest ones, platforms the size of cityscapes, will eventually shed their layers of ice, annealed over hundreds of thousands of years, and become part of the sea.

Scattered around the peninsula are several islands like the one we approached, islands that served as barely inhabitable platforms for whaling operations in the early and midtwentieth century. Today the only remnants of human civilization are occasional concrete pylons with bronze plaques identifying the area as an open-air heritage site, and leftover whale bones. After we hauled our rubber boat up on the rocks, I walked toward the spoil piles of green-stained and weathered whale bones, strewn like spare lumber at a construction site.

Reading whale bones is what I do, although sometimes I feel like the bones find me. I’ve spent so much time searching for them, cataloging them, and puzzling over them that my brain immediately recognizes even the slightest curve or weft of bone. Whale bones tend to be relatively large, so finding them is often largely a matter of making sure that you’re in the right neighborhood—it shouldn’t have been much of a surprise, especially on the grounds of an abandoned whaling station. On the island I mentally inventoried the first assemblage I encountered, as I dodged foot-tall gentoo penguins scrambling at my feet: ribs, parts of shoulder blades, arm bones, and fragments of crania. They clearly belonged to rorqual whales, about the size of humpbacks, or possibly even fin whales. Some of the more intact vertebrae were artfully balanced upright on the shoreline, probably posed by Antarctic tourists, passing through the peninsula by the thousands in the austral summer and looking for a perfect photograph.

If these bones belonged to humpback whales, it would not be surprising, given the abundance of this species out around Antarctica today. It’s likely that some of the whales that we tagged were descendants of these individuals, belonging to the same genetic lineage. But history tells us that if you turned back the clock a century, humpbacks probably wouldn’t have been the only ones here: blue and fin whales would have numbered in the hundreds, if not thousands; minke whales, beaked whales, and even Southern right whales would also have been part of the community. Ari has seen only one right whale out of the thousands of whales that he’s observed over fifteen years in the area. Southern right whales have barely recovered from two hundred years of whaling, and we know little about where they go besides their winter breeding grounds along protected coastlines of Australia, New Zealand, Patagonia, and South Africa.

It’s not just right whales that vanished. There’s no memory or record of just how many of any kind of whale there was in the Southern Ocean, in terms of their abundance, before twentieth-century whaling killed over two million in the Southern Hemisphere alone. However, as whale populations in this part of the world slowly recover from this devastation, we’re beginning to see what that past world might have looked like. On an expedition in 2009, Ari and his colleagues documented an extraordinary aggregation of over three hundred humpbacks in Wilhelmina Bay, the largest density of baleen whales ever recorded. “There is no external limit on these whales because there is just so much krill. They literally cannot eat enough before they need to leave,” Ari reflected. “That incredible resource base means that it’s just a matter of recovery time for whales—and I think what we saw in the bay that year was a glimpse of what their world was once like, before whaling.” On the whole, humpbacks have recovered to only about 70 percent of their prewhaling numbers in the Southern Ocean, although along the peninsula their population size has nearly returned to the best estimates of prewhaling levels at the start of the twentieth century.

I paused on a guano-free ledge to record a few observations about the bones’ weathering and their measurements in my field notes. To the southwest, the sky churned in a dark gray, portending wind and snow, and I felt a chill creep into my damp toes and fingertips. I pulled off my gloves and reached for a disposable hand warmer in my jacket pocket. Lodged in a mess of receipts and lozenge wrappers was a note my son had left me on the kitchen counter back home:

Im gona mis you

wen you go to

anaredica.

The night before I left my home in Maryland we traced the expedition route on a plastic globe. When he wanted to know how far away eight thousand miles was in inches, I didn’t tell him the answer that I wanted to, which was “Too far.” I reassured him that the passage was safe and that we would stay warm. “I’ll think about you when we drink hot cocoa,” I offered, dressing up my own concerns with a good smile.

As we pulled away from Cuverville Island to return to the Ortelius, the swirling clouds began to send down flurries, covering us in thick, wet snow. The boat bumped hard against the waves, and we saw humpbacks surfacing far off in the distance, the wind pushing their blows quickly behind them. The sight of those living, breathing, feeding whales in the same view as the island with beach-cast bones made me feel as though I could see the present and past simultaneously, each telling us facts that the other vantage could not. The bones on Cuverville Island and Ari’s tagging work in the Gerlache were each a unique window into the story of humpback whales in the Antarctic, though these views were terribly incomplete: the past represented by mere bones crumbling on remote shores, what we know today limited to a few hours’ or days’ worth of data collected by a hitchhiking recorder on whales’ backs.

Scientists tend to operate within intellectual silos because of the years of training and study that it takes to know about any single part of the world. But the best questions in science arise at the edges. Ari and I both want to know how, when, and why baleen whales evolved to become giants of the ocean—Ari wants to know more about their ecological dominance today, and I want to know what happened to them across geologic time. The answer to the basic question about the origin of whale gigantism requires pulling data and insights from multiple scientific disciplines, which is another way of saying that we need the perspectives of different kinds of science—and scientists—to untangle the monstrous challenges of the nearly inaccessible lives of whales. That’s why a paleontologist like me was on a boat tagging whales at the end of the Earth: I needed a front-row seat to know exactly what we can hope to know from a tag. But answering the questions that most captivate me about whales requires more than just a single tag. It means wrapping my arms around museum specimens, handling microscope slides, paging through century-old scientific literature, and wading knee-deep in carcasses.

The wind sapped the last warmth from my already-wet gloves and whipped through openings around my hood as I held tight to the ropes on the gunnels. The first scientists to visit this place, over a hundred years ago, didn’t have the luxury of disposable hand warmers. They suffered more brutally than we can really imagine, with less certainty of safe return. In these narrow margins they must have wrestled with the tension that overcomes scientists in the field: the desire to apprehend something almost unknowable against the tolls of living a world away from civilization. I patted my son’s note, folded safely inside my jacket pocket. Hot cocoa sounded just right.

I was never a whale hugger. I didn’t fall asleep snuggling stuffed whales or decorate my room with posters of humpbacks suspended in prismatic light. Like most children, I went through phases of intense study: sharks, Egyptology, cryptozoology, and paleontology. The curriculum was loosely inspired by my small curio cabinet crammed with a bric-a-brac collection of gifts and found treasures: abalone shells from my parents’ friends in California and fluorite from a great-aunt in New Mexico sat next to trilobites and fossil ferns that I had collected on family trips to Tennessee and Nova Scotia (good fossils being hard to come by on the island of Montreal). My collection was a tangible means to escape, across geography and time, as I read ravenously about dinosaurs, mammoths, and whales under the tacit encouragement of my parents, professors who recognized this type of aimless curiosity.

During one of my immersive phases, I came across a distribution map that showed the location of whale species around the world. With my finger I traced the range of blue whales, the largest of all whales, as it went right up the St. Lawrence River, which bordered my neighborhood. I wondered about my chances of seeing a blue whale casually surfacing in the distance near my house. The thought of a local blue whale was a reverie that often arose in my mind as a kid, although it took two decades for me to return to it in earnest, as a scientist.

Some branches on the tree of life become quite personal, for reasons that are difficult to explain. We seek reflections of parts of ourselves in beings seemingly close to us—the disdain of a house cat or the perseverance of a tortoise—but in the end these species are distinctly other, refashioned by evolution and eons of time away from our shared ancestry. Those differences are accentuated to the furthest degree in whales; they seem mostly other—otherworldly, really—and that makes them both fascinating and enigmatic. They embody an incongruity that is vexing because they betray their mammalian heritage in so much of what they do, yet they look and live so far apart from us. Their size, power, and intelligence in the water are astonishing because they’re unparalleled, yet whales are benign and pose no threat to our lives. They are almost a human dream of alien life: approachable, sophisticated, and unscrutable.

I don’t malign whale huggers and dolphin lovers, even if I wrinkle my nose at the rhapsodic celebrations of armchair experts. Yes, whales and their lives are superlative, foreign, and well worth epic prose. But their amazing qualities are just starting points for me, as a scientist. Whales aren’t my destination: they are the gateway to a journey of discovery, across oceans and through time. I study whales because they tell me about inaccessible worlds, scales of experience that I can’t feel, and because the architecture of their bodies shows how evolution works. By rock pick, knife blade, or X-ray, I seek the corporeal evidence they provide—their fossils, their soft parts, or their bones—as a tangible way to anchor questions that surpass the bounds of our own lives. Whales have a past that reaches into Deep Time, over millions of years, which is important because some features of these past worlds, such as sea level rise and the acidification of ocean water, will return in our near-future one. We need that context to know what will happen to whales on planet Earth in the age of humans.

Whales are so very unlike the furry, sharp-eyed, tail-wagging, baby-nuzzling animals we think of when it comes to our mammalian relatives. First off, whales are among the few mammals that live their entire lives in the water. The only fur to be found on their bodies is the hairs that dot their beaks at birth. Although whales possess the same individual finger bones that you and I do, their phalanges are flattened, wrapped together in a mitt of flesh, and streamlined into bladelike wings, no hooves or claws to mar their perfect hydrofoils. Hind limbs exist only as relics in a handful of species, bony remnants tucked deep within muscle and blubber. A whale’s backbone ends in a fleshy tail fluke, like a shark’s; but unlike a shark or even a fish, whales swim by flexing their backbone up and down, not side to side. In short, they look nothing like squirrels or monkeys or tigers, but whales still breathe air, give birth, nurse their young, and keep company with one another over their lifetimes.

Fossils tell us the earliest whales were more obviously, visibly mammalian. The first whales had four legs, a nose at the tip of their snout, and maybe even fur (up for some debate among paleontologists, as fur doesn’t readily fossilize). They had sharp, bladelike teeth and lived in habitats that ranged from woodlands with streams to river deltas, occasionally feeding in the brackish waters of warm, shallow equatorial coasts. The oldest fossils of these land-dwelling, four-legged ur-whales come from rock sequences around about fifty million to forty million years old in the mountain ranges of Pakistan and India. At the time, the Indian subcontinent had not yet collided with Asia and sat in the middle of the forerunner to the Mediterranean Sea, called the Tethys sea, which split the Old World at the equator.

The skeletons of most of these first whales were the size of a large domestic dog. Because they lived on land, you won’t find the flattened arm and finger bones we see in whales today—instead their limb bones are round and weight bearing, and their hands and feet end in elegant, delicate phalanges. Their tail, as far as we can infer from the available bones, did not end in a fluke. Their Latin names give some clues about their provenance or what makes them special. Pakicetus, for example, originates from an area that is now Pakistan, but was once an island archipelago where early whales climbed in and out of streams. Ambulocetus, a low-slung early whale with body and skull proportions like a crocodile, has a name that translates as “ambulatory, or walking, whale.” Maiacetus, one of the rare early whales for which we have a near-complete skeleton, earned its name from fetal bones preserved near the abdominal cavity of the original specimen—the mother whale. Today’s whales all give birth tail first; the rear-facing position of the fossilized fetal Maiacetus showed that whales at this evolutionary stage still gave birth on land, headfirst.

The combination of four legs, phalanges, and cusped teeth is found in no whale alive today. What made these ancient creatures whales in the first place is subtle, lodged deep in their skeletons. That’s a good thing for us because these hard parts stand a chance of being preserved over tens of thousands of millennia. One of the most important features is the involucrum, a fan-shaped surface on the outer ear bone, rolled like a tiny conch shell. Pakicetus has an involucrum, as does every other branch on the whale family tree subsequent to it. The involucrum is one key trait, along with small clues in the inner ear and braincase, that the earliest whales share exclusively with today’s whales and no other mammals. In other words, it’s a feature that makes them whales and not something else. It’s unclear whether the trait gave Pakicetus an advantage for hearing on land, but later lineages of early whales co-opted it to hear directionally underwater, using a connection between the outer ear bones and the jawbones. Tens of millions of years later, the involucrum (and underwater hearing) persists in today’s whales, from porpoises to blue whales.

Pakicetus, a land dweller, swims in an Eocene streambed.

Fifty million years of whale evolution can be split into two major but unequal phases. The first deals with the transition of whales from land to sea in less than ten million years; the earliest land-dwelling whales all belong in that first phase—even at their most aquatic, they still retained hind limbs that could have supported their weight on land. The second phase covers everything that happened once whales evolved fully aquatic lives, for the remaining forty or so million years, until today. Throughout both of these phases, extinction dominates as a constant background theme because, as with the vast majority of animal lineages on the planet, most all the whale species that ever evolved are now extinct. While they are the most diverse marine mammal group today, numbering over eighty species, the fossil record documents over six hundred whale species that no longer exist.

The first phase of whale evolution is fundamentally about transformation: the tinkering and repurposing of structures from an ancestral state (originally for use on land) to a new one, in aquatic life. Transformation requires an initial state, and some starting points in evolution can be difficult to discern. For example, hearing, sight, smell, and taste are all senses that evolved for nearly 300 million years on land before the first ancestors of whales took to the sea. While it’s convenient to think of the reshaping of hands into flippers in whales as an undoing, that’s a mistake: whales didn’t undo 300 million years of terrestrial modifications. They did not, for example, recover gills. Instead, the story is far more interesting. Whales worked with what their ancestors had as land animals, modifying many anatomical and physiological structures for a new use rather than some phantasmagoric evolutionary reversal.

The second phase, after whales got back in the water, encompasses any whale lineage obliged to spend its life exclusively in the water; this phase also spans all of the consequences that arise from that constraint. You can think of evolutionary innovation as a hack on constraint. In other words, novelty in evolution is the appearance of a totally new structure, such as baleen, that confers not just a slight advantage to those who possess and inherit it but shifts their descendants into a completely new dimension of adaptation. The second phase of whale evolution, when innovations such as filter feeding and echolocation appear and fuel the diversification of today’s whales, stretches in time from the first aquatic whales, about forty million years ago, to the present day, including all living cetaceans, along with hundreds of extinct forms in between.

In the past 250 million years, many backboned animals converted from living in terrestrial ecosystems to living in oceanic ones. The first wave happened throughout the time of the dinosaurs, when many different reptile lineages invaded ocean ecosystems from 250 million to 66 million years ago. Since the mass extinction at the end of the Cretaceous, the ecologically dominant ocean invaders have been mammals—including everything from whales to sea otters—although penguins and Galápagos marine iguanas are also more recent reentrants. All of today’s marine mammal lineages are distantly related to one another, whether it’s a whale, a sea otter, a seal, a sea cow, or a polar bear (yes, technically polar bears too, which eat seals and hop across ice-covered seas).

What makes early whale evolution so important is that the completeness of the fossil record from the early stages—Pakicetus, Ambulocetus, Maiacetus, and all others like them during that first phase—is unmatched by any other group in the fossil record. We simply don’t have the range of fossils showing the specific anatomical transformations from land to sea for any other mammal or reptile the way we do with whale origins.

Even so, the evidence for whale origins has only recently been uncovered. Until about forty years ago, we had no idea what the hind limbs of the earliest whales in the first evolutionary phase really looked like. The discovery of Pakicetus in 1981 gave us mostly bones from the neck up—paleontologists discovered a small W-shaped braincase exhibiting, among other features, an involucrum, but it otherwise looked like any other land mammal’s. They found the skull—pinched and delicate, like a handheld vase—in river deposits, and concluded that the earliest whales lived some part of their life on land. Without more of a skeleton, at the time they could only speculate about what these whales looked like from the neck down.

In 1994 the discovery of Ambulocetus clarified this picture, showing that the earliest whales had weight-bearing fore and hind limbs, with separate phalanges perhaps connected in life by webbing. Relatively large feet in Ambulocetus were a clue about its swimming style, which likely involved flexing its spinal column along with its broad feet, in one motion. Mechanically this style is somewhere between paddling with hands and feet (using drag for forward motion) and employing a hydrofoil, as modern whales do with their tail fluke (using lift, instead of drag). Our pelvis is rigidly connected to our backbone, whereas in Maiacetus, the pelvis was only partially connected to the backbone, permitting a lot of flexibility for the whole spinal column to undulate up and down. The shape of a few tail vertebrae can reveal a lot about locomotion—in Ambulocetus the fact that the tail vertebrae are longer than they are tall tells us that these early whales had long, thickened tails, although we still don’t have enough bones to know what direction these powerful tails might have moved.

Ambulocetus still didn’t provide enough evidence to help answer the big questions about whale origins: Where did they fit into the mammalian family tree? Who are their closest relatives? By the 1990s, DNA studies had shown that hippos are the closest living relatives to whales. Hippos and other even-toed hoofed mammals, such as cows, deer, and pigs, are seemingly unlikely relatives, until you look at their stomachs. Even anatomists in the nineteenth century knew that living whales had multichambered stomachs like these ungulates, pointing to a possible evolutionary relationship. Paleontologists, however, had other extinct fossil mammals in the running for whale’s closest relatives: mesonychids, which had strikingly similar teeth and were wholly carnivorous, as whales are today, but left no descendants. Without more skeletal material from four-legged whales, especially from their limbs, there was no way to parse the stories of DNA versus fossils for the deepest origins of whales.

Then, in 2001, two competing groups of paleontologists reported the same pivotal piece of evidence from different species of early whales: they each had discovered that the anklebone of ancient land-dwelling whales was exactly like those of living even-toed ungulates. This bone, called the astragalus, looks like two 35 millimeter film canisters taped together like a raft; in your hand it feels like some kind of board-game piece. Cows, goats, and camels all have it. Living whales don’t because they have no feet, and the only traces of hind limbs are reduced to nubbins of bone next to free-floating pieces of their pelvis, wrapped deeply in their body walls—making fossil hind limbs in early whales the only source for this information. Mesonychids didn’t have these double-pulley anklebones, which meant their tooth similarities with early whales were the result of convergent evolution—something that has happened frequently in mammal evolutionary history. The discovery that early whales had a so-called double-pulley astragalus confirmed the DNA findings: whales were just highly modified even-toed hoofed mammals, minus the hooves.

Since finding Pakicetus, paleontologists working in remote parts of Egypt, Pakistan, and India have discovered a rich variety of early land-dwelling whales that lived about fifty million to forty million years ago, toward the end of a geologic epoch called the Eocene. These early whales seem to have been experimenting with ecological modes that have parts both familiar and strange: Ambulocetus looked crocodile-like; Maiacetus more like a sea lion, which had not yet evolved; still other strange early whales such as Remingtonocetus were an amalgam of zoological categories, something like a long-snouted otter; and Makaracetus, named after a mythological South Asian creature that is half fish, half mammal, had a downturned snout, perhaps for eating clams. All of these early whales belonged to extinct branches at the base of the whale family tree; our expectation about what makes a whale is hindsight biased, based on how we see them today—a great challenge paleontologists face when trying to understand the biology of these extinct whale relatives.

Knowing how whales turned out makes our retelling of their evolutionary pathway a tidy, preordained story. It’s easy to imagine Pakicetus, looking something like a lost dog dipping its toes in the water, followed then by intermediate stages of creatures each spending more time in the water: Ambulocetus, which could hear underwater and lunge at prey with its powerful limbs, like an ambush predator; followed by Maiacetus, whose pelvis was less strongly coupled to its spinal column, permitting the first kind of flexibility for tail-driven propulsion in whales. Fossils belonging to relatives of Maiacetus extend over a far greater geographic range than those of previous ur-whales, suggesting that this still-quadrupedal animal was seafaring, though it still returned to the shore to give birth, like sea lions today. In this view, Maiacetus represented the last of the earliest whales; all subsequent whales, in the second phase of the evolutionary chronicle, had no weight-bearing limbs and were totally separated from land.

The problem with this linear narrative is that we know the final result, which lets us pick and choose the likely path of least resistance toward the whales we recognize today. But evolution doesn’t work like that: it makes no concession for the future; it’s about what’s good enough in the moment. Selection operates on what’s available, sorting biological variation based on the demands of the immediate world. If you were somehow able to return to a late Eocene shoreline in the Tethys sea and happen upon the entire assemblage of early whales in one lineup—all of the early whales, four-legged and odd, scattered on the shoreline—you wouldn’t be able guess the eventual winner of the evolutionary sweepstakes. In its own time and habitat, each early whale was as well adapted as any crocodile, sea lion, or otter living today. It’s just that when we work with the fossil record, we’re afforded a view of the very long run, and the relative successes and failures in any particular group over millions of years. The eventual winners of the evolutionary sweepstakes were early whales that completely severed their ties to land, becoming fully aquatic, eventually yielding descendants that filter feed and echolocate.

These first whales were merely semiaquatic mammals with specializations for life near the water to one degree or another. There was nothing predetermined about some of their descendants becoming fish-shaped leviathans many millions of years later. Retrospection, however, does cue us into specific features that show incremental transformations: shell-shaped ear bones being repurposed for underwater hearing; or the pelvis becoming unlinked from the backbone, allowing the whole back end to serve as a propulsion device. If you focus on tallying which species go extinct and which ones survive, you might lose sight of the important lessons about major evolutionary change told through bones over geologic time.

Of all the two-hundred-odd bones in a whale’s body, skulls are probably the most important part to examine if you’re interested in the big picture of whale evolution. Like the skull of any vertebrate animal, whale skulls past and present conveniently house the primary organs for taste, smell, sight, sound, and thought all in one unit. Skulls are thus rich sources of functional information about the lives of whales and their transformation over time—after all, these senses are tweaked, enhanced, or diminished when lineages undergo major ecological transitions, such as the one from land to sea, over the course of evolution. Despite their durability, skulls are challenging objects for study. Their individual bones interlock with one another in complex and hidden ways, with blind corners, overlapping parts, and delicate connections. Soft tissues such as the eyes and brain all rest across several bones, like fruit sitting in a bowl made of interconnected puzzle pieces. To make things even more interesting, whale skulls are not only intricate but big. I’ve stared at whale skulls long enough that they feel familiar to me, but I always have to remember that whale skulls are, in very clear ways, unlike those belonging to any other mammal.

Take the skull of a bottlenose dolphin, which rests comfortably on a desk but would require two hands to move carefully. It consists of two basic parts: a paddle-shaped beak, formed of elongate bones with rows of teeth like pencil tips; and a cranium of layered bones that cover a bowling ball–shaped braincase. About those teeth: You won’t find the traditional lineup of incisors, canines, premolars, and molars that mammals usually possess. At some point in their evolutionary history, toothed whales gave up chewing for merely seizing their prey with a snap of their jaws and then swallowing it whole. A bottlenose dolphin may flash what looks like a welcoming toothy grin, but I wouldn’t put my hands anywhere near it.

Moving from the beak to the rest of the skull, the next-most-obvious feature is the orbit, the bone roofing where the eye would be, like a heavy eyebrow, still very much like that of other mammals. But behind the orbits, differences begin to accumulate. First, there’s the aperture that leads to nostrils, or the blowhole. You can peer down the curved passageway formed by these nostril bones to the underside of the skull, where you’ll see an origami construction of delicate, folded bones with paper-thin edges. The bones leading to the blowhole are actually behind where the eyes would be located, the complete opposite of any other mammal, where nostrils are located at the tip of the snout. If your nostrils were positioned like those of a dolphin, you’d blow your nose from the top of your forehead.

Pakicetus, Maiacetus, and Remingtonocetus had nostrils toward the tip of their snout, and these structures slowly migrated backward in other stages of fossil whales, up to the bottlenose dolphins that we see today, with nostrils displaced well behind the eyes. Interestingly, whales aren’t alone in nostril migration: sea cows and manatees, also full-time aquatic mammals, have nostrils positioned high on the skull (though not behind the eyes), whereas their early fossil relatives have nostrils positioned more forward. This parallel migration of the nostrils lets fully aquatic mammals, such as whales and sea cows, orient their body in a more energy-saving horizontal position in the water, as opposed to doggy-paddling with their nose out of the water. But swimming horizontally is just part of the reason for the strangeness of the bottlenose dolphin skull before us.

When viewed from the side, the top of a bottlenose dolphin’s skull is shaped like a scoop—if you were a dolphin, imagine having a skull with a dishlike forehead, right above your eyebrows. In life, for a dolphin this cavity contains a cone of fat called the melon, which gives toothed whales a domelike forehead. Tucked behind the melon, and underneath the blowhole, are empty sacks: air sinuses underlain by muscles and sealed with an organ that looks like a pair of lips. When these lips buzz like a trumpeter’s, they generate sound, which bounces around the inside of the head and then gets focused by the melon into a discrete path out of the head, as a high-frequency sound beam, like an acoustic beam emanating from a searchlight strapped to the dolphin’s forehead.

By coordinating this process across a specialized set of anatomical parts to generate sound, toothed whales create a form of biological sonar—or echolocate—to see their underwater world in sound. All toothed whale species alive today echolocate, whether they are sperm whales, beaked whales, river dolphins, porpoises, or true dolphins. It’s how they wayfind, or hunt, in murky rivers or at ocean depth, sometimes a mile deep, with no light. Echolocation itself has evolved only a handful of times in other vertebrates; toothed whales are the only animals that do it underwater.

Making high-frequency sound, however, is just one part of echolocation; after sound bounces off an object, it produces an echo that the animal needs to hear. (The classic dolphin chirps and squeaks are how they vocalize to communicate with one another at lower frequencies.) We can’t hear directionally underwater, but whales can because their ear bones float inside hollow pockets. In life, the ear bones of a dolphin hang in a sinus cavity full of spongy tissue, which acoustically isolates each ear, letting the brain detect small differences in the arrival time of sound between the right and left ear, helping to pinpoint the source in three dimensions. Whales have had the ability to hear like this since bthe time of Ambulocetus.

But how does sound get to the ear bones, especially when whales don’t have external ears? Fats are conductive of sound, and along with the melon, toothed whales have large, fat bodies that fit hand in glove into hollows in the backs of their jaws and then branch out, backward, into lobes that directly connect to the ear bones. Akin to the way our ear canals funnel sound, these fat bodies provide a pathway for sound to reach the ears, although researchers still debate whether there aren’t other acoustic pathways in the head—testing the anatomical basis for echolocation requires clever experimental work, and captive animals are not easily procured. This hallmark sense in toothed whales was poorly understood until the late 1950s, when scientists, supported by strong interest from the U.S. Navy, resolved the enigmatic echolocation abilities of toothed whales in a simple way: after covering a captive dolphin’s eyes with suction cups, they discovered that the animal was still able to navigate a maze to find a small object.

We still know little about how echolocation in toothed whales truly works, especially in wild, free-ranging animals. It surpasses even the best military technology, and we’re just starting to understand the basics. There is marked variation, from species to species, in terms of the arrangement of air sacs, melon shape, and even ear bones. What any one of those differences means for sound frequency and how whales perceive it remains a broad mystery, hopefully the work of future dissertations. We can say, however, that a quick tour of a dolphin skull shows us how evolution refashions or modifies existing parts—like nostrils displaced behind the level of the eyes—while other times it generates completely new structures, such as a biosonar apparatus on the forehead. How evolutionary novelty happens remains one of the most important unanswered questions in biology today.

Transformation and novelty are recurring themes in whale evolution as much as they are for any group in the tree of life, and it is sometimes difficult to parse the distinction between them. Consider how the feathers that most birds use today for flight are elaborations—transformed many, many times over—from basic scales that once covered their dinosaur ancestors. Or how turtles, early in their evolutionary history, acquired shoulder blades inside their rib cage; turtles’ ribs later fused with other bones so that every turtle thereafter, for the past 200 million years, has had a shell with its shoulders tucked firmly inside. In both of these cases, evolutionary novelty does come from somewhere in the body—it’s an extreme flavor of transformation that starts with some available parts—but novelty is different because of its consequences. Whereas a transformation can be the reduction of parts or a change in size or proportions, a novelty is a one-time evolutionary appearance of a new structure that enables the evolutionary success of all of its descendants. Today’s whales are exemplars of the great success of evolutionary novelty, with echolocation in toothed whales and filter feeding in baleen whales enabled by biological apparatuses present in none of their forebears.

Evolution is the intellectual glue that connects living whales, in all of their seeming weirdness, to their deep ancestry, which is both incomplete and still not entirely known. Skulls point us to these evolutionary clues in a tangible and clear way; and without these insights, and the millions of years that brought these changes about, it would be very hard to illuminate the connection whales have with other closely related mammals.

My way back to whales, as a scientist, has always involved skulls in one way or another. In college I puzzled over a half-rotten dolphin head when our field class, on a barrier island off the coast of Georgia, discovered its carcass buried in the sand. The putrid smell dispersed the rest of the class, but I held fast. I wasn’t riveted by the grotesque allure; instead I was captivated for the first time by the thought of how, exactly, a whale might become a fossil.

In graduate school, I sought fossil whale skulls peeking out of seaside cliffs or crumbling out of rock formations in badlands that were once seafloors. Cetaceans became my vehicles for understanding life over geologic time, across scales so vast that we cannot truly comprehend them, even if paleontologists casually discuss geologic markers as if referring to last week’s dentist appointment. And it all led me to the Smithsonian, where I tend to the world’s great collection of fossil whale skulls.

However, part of the deal with being a museum scientist, especially at the Smithsonian, is that people ask you for tours. It’s more than a fair trade. First, I like giving tours. They give me an excuse to try out new ways to talk about ideas—the big ones, like the evidence for evolution and extinction—that not only excite me but also explain how whales came to be. Also, tours often involve children, and children are usually the toughest audiences of all, whether they’re whale huggers or fossil fiends. If I can figure out how to keep them interested, even for a short show-and-tell, then I think I’ve done my job. And who knows, I might even be convincing enough to ignite more than a passing interest.

My friend and colleague Megan McKenna first taught me about whale heads and their inner biosonar anatomy when we were both in graduate school, so when she brought her family recently for an early-morning tour before the museum opened, I was excited at the opportunity to settle a debt. Her four-year-old daughter was just a bit older than mine. The museum’s halls, especially when they’re empty, can be intimidating spaces, so I started slowly—I didn’t want to overwhelm or manufacture too much excitement.

As we walked into the Sant Ocean Hall, we stopped short underneath the imposing right whale model, and turned to face the eel-like skeleton of Basilosaurus, grimacing from above. Basilosaurus is an early whale several million years younger than Pakicetus and Maiacetus but it looks worlds apart in size and shape. Its dinosaur-sounding name literally translates from Latin as “king lizard,” in a nod to its serpentine, bus-length body. The first fossils of Basilosaurus were collected from the chalky marls of rural Arkansas and Alabama in the early nineteenth century. With a skull over three feet long, jaws bearing palm-sized, saw-shaped teeth, and individual vertebrae large enough to serve as stools, a Basilosaurus skeleton gives every impression of belonging to a sea monster—and its name has stuck, if only for the conventions that scientists use to name species.

Unlike today’s whales, Basilosaurus has a head that does not dominate its body, arms that crook at the elbows, and a surprising, diminutive set of legs that could never have supported its large weight on land. But Basilosaurus has an involucrum like all the other early land-dwelling whales, and its ear bones floated in a sinus space below its skull. Basilosaurus did not echolocate, nor filter feed, leaving it caught somewhat in an evolutionary middle ground for whale evolution: one of the first fully aquatic whales, completely unreliant on land, yet still carrying many of the biological apparatuses of its terrestrial ancestors.

A Basilosaurus tooth

As I walked with Megan under the skeleton, I pointed to its hind limbs and joked aloud about how they dangled like poorly placed, miniature landing gear. Megan then leaned down to her daughter. “Hey, Etta, Nick studies whale bones just like those ones.” Etta looked at me intently, mulling the assertion. “Why?”

I opened my mouth to deliver a canned response involving school, science, and curiosity, more boilerplate than authentic. I knew I could do better. I waited a few beats.

“Their bones all tell stories,” I said, “about where whales came from.” She glanced up at Basilosaurus looming from the ceiling, like a giant, flippered, macabre snake. “And if you become a scientist, you can learn to read them and know their stories.” I knew I had her attention. “But they sure don’t just show up here in the museum all put together,” I smiled. “You have to find them first.”

I walked with my eyes trained on a long, gray road cut through a hillside on a cattle ranch. In the late-afternoon California sun, the waving golden grass gave the hill the look of an enormous, shaggy animal, revealing its sedimentary flank. I followed a small path, parallel to the exposed fossil-rich layer. Walk, stare, walk some more, scrape the exposure, and then walk again; maybe you get lucky.

A few yards away from me, my colleague Jim Parham was doing the exact same thing. I’ve known Jim since graduate school, and we don’t need to say much to each other in the field. Jim’s an expert on turtles and other reptiles. As it is for me with whale bones, Jim has seen enough specimens that even the smallest fragments of fossil shell can help him solve riddles about turtle origins, which stretch back even deeper in geologic time than whales, though we tend to find fossil sea turtles in the same type of rock as fossil whales. Jim and I reliably fall on the same page, by temperament and by rock units.

We had visited many other outcrops in the foothills of the Sierra Nevada together. We worked side by side, scanning in silence. “Hey,” Jim said abruptly, reaching down. He raised a palm-sized shark tooth to the sky, its serrated edges cutting the orange light. I looked down and immediately started to see other shark teeth and whale bone fragments recently eroded out of the hillside, gems in the rough. “Oh, check this out,” I said, retrieving a segment of dolphin rib from the newly formed sediment piles. As I flipped it over between my fingers, I noticed something unusual—a set of a dozen parallel lines gouging a path across the bone’s surface. A shark bite. This site was, after all, the Sharktooth Hill bonebed.

The fact that the rib bone belonged to a small species of extinct toothed whale (Odontoceti indeterminate, if you want to be technical) was probably the least interesting thing about it. That kind of identification is merely born out of the same patient study—hours with museum collections—that gives you eyes for spotting bones in the first place. Far more interesting was the fact that it told us part of a story: a little more than fifteen million years ago, in the middle of the Miocene, an ancient shark chomped down on an extinct dolphin’s rib cage.

Whether this particular set of bones represented a fatal encounter or mere scavenging on a carcass we couldn’t know. There was also no real way of knowing whether the shark tooth in Jim’s hand and the marked rib in mine were causally related. We held the two side by side, checking the serrations on the tooth with the gouges on the rib—close, but not a precise match. Even if they were, it would be a stretch to tie the two pieces of evidence, a gumshoe’s leap in causality at a suspected murder scene. Whale bones do tell us stories, but they’re not always satisfying or predictable.

I lodge finds like these on the shelves of whale bones that I keep in my head. I can’t quite tell you how this mental library is organized, but I slip into it every time I see a shard or glint of whale bone, whether out in the field or in a museum drawer. The more fragmentary, the more fun. I pick it up carefully, thumb its creases, divots, and twists, and then scrutinize its topography by eye. My thoughts immediately race through a chain of mental flash cards to arrive at the best possible identification of its former owner: Right or left side? Symmetrical, from the main axis of the skeleton? Cranial or something below the neck? Scavenging marks? Pathologies? These flash cards are marked with names for every bump and hole on a bone’s surface. It has taken me years to build up this cerebral collection, long hours spent with many skeletons within arm’s reach, flipping each piece over and over again, tracing each surface for memory. It’s also good to keep a stack of real literature on hand as a guide, because you certainly aren’t the first one to pick up a whale bone and ask it a question: How did you get here? Where in the skeleton do you belong? What happened to your owner? There is an undeniable thrill in this chase, whether it’s in the field or in a museum collection, and fortunately you carry your mental library everywhere you go. Anyone can participate too—amateur sleuths sometimes crack cold cases.

There is, however, a catch: you hardly ever get all the answers. As with other vertebrates, the fossilized skeletons of whales tend to be massively incomplete because the organismal glue that keeps skeletons together—stuff like ligaments, fibers, cartilage, and muscle—decays rapidly and is dispersed by waves, scavengers, and time. Our knowledge of most fossil whale species is based on little more than a battered skull, lacking all but the most diagnostic and unique features. For some time periods, and in some parts of the world, we can put all of what we know about the whale fossil record on one table. These fragments of bones—skulls, teeth, vertebrae, limb bones—can look like a jumbled puzzle waiting for someone to bring the missing pieces. Or, preferably, the cover of the box.

This situation is what we tend to find for most fossil whales from the first phase of their evolutionary history, the part that took place at least partially on land. We don’t have complete skeletons for Pakicetus, Ambulocetus, Remingtonocetus, or most of the close relatives of Maiacetus. Being aquatic clearly helps in getting preserved intact. Perhaps the size increase from Maiacetus to much larger early whales such as Basilosaurus is part of why we tend to find more complete skeletons belonging to fully aquatic whales (while the bones individually get larger, they are fewer in number when you reduce and eliminate paired leg and foot bones). The fact is we don’t have a good understanding of the intermediary steps between hind-limb-propelled whales to tail-propelled ones. For all the anatomical transformations that happened in the earliest whales, there is a gap in the fossil record and our understanding between the last semiaquatic and the first fully aquatic whales. To fill out the picture we need more fieldwork in the right places with rocks of the right age, and a lot of luck.

A good paleontologist can go far on scraps alone, and sometimes we’re lucky. There are places—or times, because paleontologists think in both space and time—where the fossil record yields parts of hundreds and even thousands of individuals. These fossil-rich areas are called bonebeds. My mental library comes in handy when I encounter one, helping me distinguish a scrap as the bone of a whale versus that of any other animal. At their densest, fossil whales in bonebeds get jumbled with scraps of other extinct marine mammals, seabirds, sea turtles, and sharks into layers only a few inches thick. At the other end of the spectrum, complete whale skeletons can be distributed over a broad area that can even reach square miles. The definition of a bonebed has mostly to do with the fact that skeletal parts are concentrated within a single layer of rock. What paleontologists and geologists want to know, once they’ve found a bonebed, is how much geologic time has compressed the evidence, which can represent as much as a million years or maybe just a day’s worth of a flood.

In the 1920s one of my predecessors at the Smithsonian, Remington Kellogg, recognized that the Sharktooth Hill bonebed in the foothills of the Central Valley contained a richness of fossil whales, mostly identified on the basis of broken skulls and individual ear bones. The bones that form the outer, middle, and inner ears of whales are among the most heavily mineralized bones for any mammal. All the better for hearing underwater—and for preservation in the geologic record. The acoustically isolated ear bones discussed previously in bottlenose dolphins can also be found back to the time of the Sharktooth Hill bonebed and beyond, to the age of Pakicetus.

Kellogg described and named twelve previously unknown fossil whale species from the Sharktooth Hill bonebed, encompassing a range of extinct baleen whales, early sperm whales, oceanic dolphins, and distant relatives of river dolphins. At this point in whale evolution, the world was full of filter-feeding and echolocating whales—all land-dwelling ones were long extinct—but they lived alongside sea cows, strange, hippolike herbivores called desmostylians, early seals, and early walruses.

The material record of that past world comes from the Sharktooth Hill bonebed, which is an orange and brown layer only a few inches thick, chock-full of bone bits spread over a dozen or so square miles northeast of Bakersfield. Jim first introduced me to the bonebed in my early years of graduate school—he was more interested in its fossil sea turtles. Eventually I focused on figuring out the precise age of the bonebed and how this kind of dense rock unit, full of bone nuggets and occasional skeletal parts, came to be. Context is everything, and without it, answers to the bigger ecological questions about the past are undecipherable.

The bonebed was essentially an exposed seafloor for several hundred thousand years, collecting the hard-part remnants of Miocene whales, sea turtles, sharks, and other animals that fell to the seafloor while lighter sediment swept past. Those few inches of bonebed today thus capture a condensed interval of time, between sixteen and fifteen million years ago—not much for a geologist but a span much longer than the duration of our own species. It’s also a span of time probably long enough to sample the full range of extinct whales and other backboned animals that lived in the vicinity of this part of California when the Central Valley was an embayment open to the Pacific. Knowing how many fossil whale species were around, giving them all scientific names, and understanding their evolutionary relationships is all ongoing work because there’s so little skeletal material to use as a basis for a species. (Kellogg used ear bones for most of his species, a puzzling move given how limited they are for species-specific identification.) Such work is time-consuming and exacting, measuring and comparing scraps of bone to one another. Many times we’re simply left saying, “This is something new, and it deserves a name, but we can’t say more until someone finds a good skull.”

Kellogg wrapped up his Sharktooth Hill work after finishing his dissertation and secured an appointment at the Smithsonian in Washington, D.C., where he turned his attention to fossil whales that were more complete, from an earlier time in whale evolutionary history. By the 1930s, the Smithsonian possessed the world’s most extensive collection of early whales, but they weren’t the land-dwelling ones, such as Pakicetus, whose skeleton still wouldn’t be found for another half century. Instead, there were drawers and drawers of Basilosaurus and other species of the first of the fully aquatic whales, more than enough to mount full skeletons for exhibit halls, and sufficient to know something about what these extinct whales were like.

Basilosaurus hardly seems like a whale—saying it’s almost like a whale would be charitable. It had a toothy, snout-dominated head, looking something like a gigantic leopard seal, except its nostrils were located not at the tip of its snout but about halfway farther back. It had a visible neck, unlike most of today’s whales. While its fingers and hands were probably encased in flesh, forming a paddle, it could bend its arms at the elbow, as no living whale can. The most remarkable thing about it was its long, eel-like body—most of its length came from its tail. Basilosaurus probably had a tail fluke, but it also had cartoonishly small hind limbs. These hind limbs were vestiges from its land-dwelling predecessors; as mentioned previously, they could not have held up Basilosaurus’s enormous weight (about six tons) on land. In other words, Basilosaurus was fully aquatic, living its entire life underwater.

Kellogg knew only a little about those tiny hind limbs—the collections at the Smithsonian, for all their depth, still comprised only a pelvis and a single femur. Did Basilosaurus have feet? Toes? The answers to those questions eventually came from Basilosaurus skeletons found in Egypt, a world away from the coastal plain of the United States, and many years after Kellogg died.

Since the nineteenth century, paleontologists have known that the same strata used to build the pyramids of ancient Egypt harbor marine fossils, including fossil whales. These fossil-rich rocks crop out for nearly a hundred miles to the southwest of Cairo, exposed at their grandest scale in a place called Wadi Al-Hitan, loosely translated as “Valley of the Whales,” in the Fayum depression. Toward the end of the twentieth century, more detailed work in the area produced a species list including ten different early whales, along with early sea cows, primates, and the earliest elephant relatives. Wadi Al-Hitan, however, earned its name because of the fossil whales—especially Basilosaurus—whose skeletons number in the hundreds, spread across miles of desert expanse edged by cliffs and wind-battered mesas. These skeletons come from bonebeds, just in a different mode from Sharktooth Hill. Over three hundred skeletons of early whales are littered across one hundred square miles, including the first complete Basilosaurus skeletons ever found, with skulls, arms, rib cages and tail vertebrae, and legs—everything down to the four tiny toes intact. What these legs might have done in life, beyond being mere vestiges, remains unclear. (Some scientists have speculated that these small legs might have been used for copulation, especially given the animal’s extreme snakiness.)

Complete skeletons of Basilosaurus give us plenty of clues about its behavior. Like some of its predecessors, Basilosaurus had acoustically isolated inner ears, letting it hear directionally underwater, but it lacked the anatomical space to house any kind of echolocation organ on its face. (Basilosaurus therefore heard only low-frequency sounds—not the ultrasonic ones that echolocating toothed whales use today.) It ate fish, based on fossilized stomach contents. Every tooth in the head of Basilosaurus was capable of crushing bone, and its overall bite force exceeded that of any other mammal, living or extinct, including hyenas. Bite marks on the skulls of another, smaller species of early whale from the Fayum suggest that Basilosaurus ate other whales, the way killer whales do today. One major difference with killer whales: Basilosaurus could crush its food, whereas killer whales rip and tear, oftentimes working together. At the moment, we can’t say whether Basilosaurus moved about in pods—there’s no good fossil correlate for that kind of behavior.

Basilosaurus

The fossil-rich rocks of Wadi Al-Hitan reflect ancient shorelines formed during episodes of periodic sea-level rise and fall at the end of the Eocene, around 40 million to 35 million years ago. Basilosaurus probably inhabited these lagoonal environments (it certainly was buried in them); it lived not unlike many dolphins do today, ranging from coastal shores to open water. By the time Basilosaurus went extinct, at the end of the Eocene, subsequent branches in the whale family tree leading to today’s whales had already evolved. While we don’t have a good fossil record for the very beginning of today’s echolocating and filter-feeding whales, we suspect they looked a fair bit like Basilosaurus—fully aquatic, though less snaky, sized-down shadows of the leviathans that they would later become, tens of millions of years later.

So much for the hows of fossil whales with legs. But why? What led whales to return to the water from land in the first place? That question takes us to the gap between the first and second phases of whale evolution, the gap that remains in the family tree between the branches leading to Maiacetus and Basilosaurus. In about ten million years, whales went from looking like the four-legged Pakicetus to something closer to Basilosaurus. Sometime during that interval (and probably in the last half of it), whales ambled and swam equal amounts, with shorter hind limbs and blowholes migrating backward along their snouts. And then, at some point, a generation of whales never emerged out of the water back onto land, and their descendants begat blue whales, humpbacks, sperm whales, dolphins, and every other living whale species (along with many extinct ones, like Kellogg’s finds from the Miocene).

The search for true causes—especially in the evolutionary sciences—is usually not as conclusive as the search for patterns and their data. Hows are much more forthcoming than whys. For whale origins, multiple explanations for their reentrance abound: they returned to escape predators on land; to take advantage of more prey at sea; to seize new habitats unexploited by any major marine predator since the demise of gigantic marine reptiles at the end of the Cretaceous, about twenty million years prior. Each one of these explanations is plausible but difficult to test. Maybe we’ll one day refine those explanations into a hypothesis with a prediction that we can evaluate, perhaps using the geologic context of these early whales, comparisons of their osteology with those of marine reptiles, or a novel analytical tool. One thing for sure: we will certainly benefit from more fossils—so we should keep looking.

Every scrap of fossilized bone found in the field may be novel, but they’re not all precious. There’s always some decision making about whether any particular fossil should be collected in the first place. It is, really, all about the questions at hand and how any certain fossil find can help answer it. Bonebeds are like caches of evidence: areas rich with clues, either because of the density of remains contained within them, as at Sharktooth Hill, or because of the completeness of the specimens in a given space, as at Wadi Al-Hitan. One fossil find can tell us about that individual, but it also captured a snapshot of a real ecological interaction, lost in geologic time. That’s an important detail from life in the distant geologic past, especially when we want to know the details of not merely the anatomy or evolutionary relationships of extinct organisms, but the food webs and ecosystems in which they lived millions of years ago. Finding these kinds of paleontological caches is thrilling, and it can also be overwhelming, as I would soon find out for myself.

Imagine floating above the great tapered tail of South America from space, seeing it stripped of clouds, ice, soil, and water so that the geologic world beneath is made visible. The familiar outline of the continent rises in stark, jagged relief. The high spine of the Andes is draped in red and gray bands to the east, toward Argentina, and ochers and sands cover Chile to the west. From this vantage, the cone of South America is locked in by a jigsaw puzzle of oceanic plates, and a surprisingly deep, dark cut mars its western boundary.

This incision marks the border between the Nazca and South American tectonic plates, where the lip of the former inexorably and slowly rolls under the edge of the latter. This action uplifts what was once seafloor, carrying ancient organisms buried in it—extinct whales included—slowly to dry land on the western edge of South America. This tectonic motion, called subduction, eventually yields mountain chains like the Andes over geologic time. But at the scale of human lifetimes, subduction can cause megathrust earthquakes that convulse entire cities, maroon fishing boats, and kill thousands in a span of seconds.

In 1835 a young Charles Darwin observed the outcome of this very process along the coast of Chile, near Concepción. Three years into its round-the-world voyage, the HMS Beagle had rounded the horn of Tierra del Fuego and made its way up the west coast of South America. Darwin was ashore when the earthquake started. A crescendo over the course of hours allowed most of the residents of Concepción to flee and limited the scope of fatalities to a few dozen people. Aftershocks rattled terrified locals for several days thereafter. Darwin later surveyed the devastation in Concepción firsthand, noting that most of the city was flattened, burned, or flooded by an accompanying tsunami—and that the entire shoreline of the harbor had risen several feet, stranding limpets and starfish. Darwin surmised that these catastrophic effects were connected with the volcanic eruptions he had observed during earlier forays hundreds of miles south near Chiloé. Darwin suspected that volcanic eruptions, the sudden uplift of coastlines, earthquakes, and tsunamis were linked by a common underlying mechanism. His intuitive guess was more right than he could have known; they are all consequences of subduction—the jerky slippage of great masses of tectonic plates against one another—and the central process that underpins the idea of plate tectonics.

Plate tectonics is a very young idea about how the Earth works. Until the late twentieth century, geology textbooks did not have a clear answer for why South America’s eastern edge fit so nicely with the west coast of Africa, which is a bit like launching moon-bound rockets without knowing Newton’s physics. Eventually scientists discovered that convection currents from deep inside the Earth drive the fragmented crust of the Earth’s rocky surface into constant motion, over geologic time. Every continent, and the ocean plates between them, floats on a vast, molten, and churning globe. The idea of plate tectonics also neatly explains a variety of patterns in the fossil record, including why so many plants and extinct animals across the southern continents look so similar—namely because they were once, a hundred million years ago, living together on a larger continental mass that has since broken apart.

Before he started thinking about evolution, Darwin was a geologist, one with a long view of history and the planet. Deep Time was a new idea when Darwin roamed the South American cone. What he saw there—the earthquake at Concepción, petrified forests in the high Andes, and fossils of extinct land mammals in Patagonia—resonated with the concept of an unfathomably old planet, one that had actually weathered many billions of years, time enough for the power of selection to yield finches, tortoises, and whales.

Darwin spent his last days in South America on horseback in the Atacama Desert of Chile, geologizing away at any exposure of inner Earth while en route to meeting the Beagle, which was moored along the northern coast near the town of Caldera. From there he headed north and westward by sea, eventually to the Galápagos Islands. Textbooks celebrate Darwin’s few weeks on the Galápagos but tend to minimize the fact that he spent two years in the South American cone. He never returned to Chile, but his social network continued the work he had begun. Correspondences born out of a shared love for the land, and scientific questions about it, roused a generation of Europeans who decamped for its rugged, open landscapes. The result is a testament to the strength of friendships that can transcend generations: they established the first centers of learning in Chile, including a national museum, whose collections still hold fossils that Darwin collected over 180 years ago. When you open up museum drawers and handle those specimens, you realize that these physical objects connect scientists across centuries, anchoring the questions that we have about evolution on this planet.

Sweeping offshore of the Atacama is the Humboldt Current, an enormous, ever-flowing body of water that cannot be discerned by the naked eye. Its namesake is a scientific figure of impressive breadth and accomplishment who preceded Darwin by decades—although Alexander von Humboldt never made it south of Lima, Peru. Today the Humboldt Current is renowned as one of the richest fisheries on the planet. Open any can of anchovies or sardines, and there’s a good chance that its contents came from the ocean current that stretches from Chilean Patagonia to Peru and the Galápagos.

Understanding how the Humboldt Current works, in the simplest terms, requires a step back to look at the coastal phenomenon of upwelling. When the Earth spins on its tilted axis, hot air rolls unevenly off the continents and transforms into trade winds over open ocean. These winds push hot water away from coastlines, and in its place arise enormous spirals of nutrient-rich water from the ocean’s depths, in a process called upwelling. Westerly coastlines across the world, from California to Chile to Angola, all share the right set of geographic features for this process. Upwelling forms the foundation for rich and productive ocean food webs because of the nutrients brought up from the deep: ocean water at the surface generally has enough oxygen, but it’s upwelling that carries nitrogen and phosphorus into shallower waters and enriches them by fertilizing both light-fixing phytoplankton and their consumers, zooplankton. The oceans may be vast, but upwelling creates specific places where these tiny organisms gather. Where there’s food to eat, that’s where whales, sardines, and penguins all want to be.

And if you’re a whale paleontologist, you want to be on the coast nearby, where upwelling and subduction combine in a perfect way. Upwelling gives us whales, and ultimately their remains—whale bones—to look for, while subduction uplifts ancient seafloors to dry land. Along with these two processes, the accident of the Atacama’s latitude makes the entire desert a gift for scientists seeking rocks: it’s devoid of grass, trees, and the blacktop of civilization. Arid and exposed badlands allow erosion to exhume the remains of ancient whales locked in rock without the interference of soil or tree roots.

Erosion helps, but paleontologists also have to find the right kind of rocks. Of the three categories, igneous, metamorphic, and sedimentary, for fossil whales only sedimentary rocks will do. Whales don’t preserve well in volcanic lava flows, and fossils hardly ever survive the tremendous heat and pressure that creates metamorphic rocks dozens of miles beneath the Earth’s surface. Among the array of sedimentary rocks, the most promising ones include mudstones, representing offshore seafloors, and sandstones, representing nearshore ones. Thanks to uplift, the only way to find fossils in the Atacama involves rolling across washes and mesas by foot or truck, finding these rocks, and keeping an eye out for a glint of bone. Whale bones tend to be relatively big, after all.

Since Darwin’s time, many thousands of bits of bone and teeth have been collected from the Caldera Basin, some ending up in natural history museums such as the one in Santiago, founded by Darwin’s correspondents. Fossil collections from Caldera consist almost entirely of fragments of skulls, limb bones, and teeth—never complete skeletons. But the little they show suggests that the Humboldt Current of the past was different: familiar species such as whales, sharks, and sea turtles lived alongside bizarre extinct ones, including nightmarish bony-toothed seabirds, long-snouted aquatic sloths, and school bus–size predatory sharks. When I started to contemplate working in the Atacama, the problem was that we didn’t have precise ages on all of these fossils in hand—we needed one complete chronicle of rocks in the Caldera Basin. Minimally we needed to identify the correct succession of layers these fossils came from, identifying oldest to youngest; at best, we hoped to pin down the ages of each fossil-bearing layer with numerical geologic dates. Once that context was arranged, we would be able to chart the rise and fall of each species over millions of years, against the backdrop of broader changes to ocean temperature, sea level, and circulation. Wear a geologist’s hat, find whale bones, and figure out the story of how the Humboldt Current’s ecosystem came to be.

After years of planning, correspondence, and false starts, I found myself sweating in the glare of the Atacama sun. I paused from scanning a geologic map of the Caldera Basin, spread across the hood of the Toyota pickup, and squinted, hoping to catch a glimpse of people summiting the flat top of a mesa in the distance. The harshness of the white light pinched my vision, split between the patchwork of colors on the map before me and the pale-blue dome above my head. I was frustrated, my mind elsewhere. We were late. The students on the field team hadn’t reconvened at the agreed-to time and we needed to keep moving.

We had followed the whale bone trail in the Atacama, and the trail led us straight into fault lines—many of them. Finding fossils wasn’t exactly our problem. Instead, it was their context. We were having a difficult time piecing together the succession of rock layers in which we were finding them. As tectonic processes uplifted ancient seafloors, they also broke them up, like a layer cake dropped on the floor. Consequently, deciphering the specific old-to-young sequence of layer upon layer of rock was complicated by long, vertical fractures that displaced the layers up and down relative to one another. We tend to think of geologic faults as stretching across hundreds of miles, and that’s certainly true for some of them. But they also manifest locally, in a rock outcrop that may be no broader than the side of a house. In the Caldera Basin, faulting sometimes created a jumbled layer of rock rather than a neat stack.

With boots on the ground, building a single chronology of rocks meant finding specific places where we could measure the thickness of the rock layer in a repeatable way, using a simple geologic tool called a Jacob’s staff. We would also note the composition, color, and texture of each rock layer. Occasionally we would also hammer out a sample of the most promising rocks—usually the ashes—in the hope of finding tiny volcanic grains that would yield precise geologic dates back in a laboratory. Through this slow, exacting work of measuring, describing, and sampling, we hoped to pin down actual dates in geologic time for enough layers in the sequence to understand the succession of different extinct species, whales and otherwise, that once lived in the Humboldt Current.

Back at the truck, however, I wasn’t thinking about geologic maps or envisioning layers of fossil whales captured through time. Instead, I was thinking about hours wasted, miles away from the air-conditioned convenience and sprawling desk work within my museum’s walls. I thought about all of the effort and time—coordinating airfares and truck rentals, pushing permits along, accounting for family and professional commitments. As the students crested the mesa, I waved at them. What I really wanted to do was slam on the truck’s horn until it was out of air.

Carolina Gutstein, my friend and colleague, then finishing her doctoral degree, stood with me at the truck. “You know, you can’t just rush people,” she leveled, without hesitation, sizing up my agitation like a sibling. “Trying to make things go faster here is only going to make them go a lot slower.” I laughed ever so slightly but stopped when I turned to look at her. Caro’s face was dispassionately still, her mountaineering sunglasses reflecting a stereo double of my own weary glance. I looked down in frustration, back toward the map on the hood, and exhaled. When I glanced her way again, she smiled, breaking the tension. “Why don’t we go see all those whales at Cerro Ballena?” she offered. “I’ll call Tuareg to show us around. He and Jim are over there now. You’re not going to believe it.”

Actually, I thought that I had good reason not to believe it, especially if it involved the man who calls himself Tuareg. His real name is Mario Suárez, and he is probably the single best fossil finder I have ever known. He demurs when asked, but Mario’s self-appointed nickname is clearly meant to evoke the stoic Berber people of the Sahara—an image he routinely betrays by losing his cell phone (he has lost more than a dozen) and completely going AWOL when needed (usually found at the nearest bakery). But at the time, we were strictly in his domain, working under his collecting permit, which he held as curator at the local paleontology museum in the town of Caldera.

Tuareg had e-mailed me earlier that year about a place he started to call Cerro Ballena, where he said complete whale skeletons had been found, but I’d had a hard time discerning much from afar. I remembered having seen the site on a past visit, a sloping road cut of the Pan-American Highway that trenched through a layer cake of orange and tan marine rocks. The only fossils I had noted were a smattering of skull bones from a large whale, likely a baleen one. Locals had tried tunneling out the bones, unsuccessfully, next to graffiti carved in the soft sandstone. None too auspicious. Fossil whale skulls are sometimes a jumble of broken bones that hardly make sense at the rock outcrop and require care and study back at a laboratory. Also, they almost always involve heavy logistics that simply outstripped our time, our resources, and, to be frank, my motivation.

Caro’s suggestion reminded me of that whale skull we had seen together by the side of the road, although I was only burdened by the recollection to a point. If we had more time, maybe we could collect it, but we had to make hard decisions on the use of our time. We were in the Atacama to understand the evolution of the Humboldt Current ecosystem, as read from layers of fossils from dozens of species across time—doing so offered the chance to find out much more than a single broken-up baleen whale skull could ever tell us. Constructing a single stratigraphic column from the stacks of rocks across miles of fractured desert terrain was something reasonable and feasible to achieve during a single field season, if not particularly sexy. I was also on the hook to deliver publications out of our work, as a foundation for future collaborations. As it turned out, I had no clue how wrong I was about the importance of that broken-up skull at the side of the road, nor a hint about the scope of what it represented.

If I was ambivalent about seeing Tuareg, at least I was buoyed by the thought of reuniting with Jim Parham. Jim is a like-minded scientist, a friend, and a terrific sounding board. His finely tuned bullshit detector always checked my field decisions about logistics. Earlier that day, we had split the field team in two to maximize our time: Caro and I took the students to the south, while Jim and Tuareg went north to Cerro Ballena. “I really don’t think we both should be in the same truck as Tuareg,” I said to Jim at breakfast. “Oh—just as a matter of sanity,” he assented.

When Jim, Caro, and I had visited Cerro Ballena with Tuareg several years earlier, we’d referred to its location as “that road cut next to Playa Pulpos,” taken from the nearest highway sign. By late 2010, it had become Cerro Ballena—literally “whale hill” in Spanish—if only because of global geopolitics, in this dusty part of the Atacama. In the past few decades, Chile’s geologic resources have become prized targets for extraction by the mining industry, and accommodating large mining machines has meant road widening along remote parts of the Pan-American Highway. An environmental-impact study at Cerro Ballena concluded that further expansion would very likely uncover more fossils. Nevertheless, a road-construction company was green-lighted to begin widening the highway. To comply, the company enlisted Tuareg and his museum for assistance, with Chile’s strong natural patrimony laws ensuring that any fossils would be saved. It was then that Tuareg had started sending me clipped e-mails and shaky videos from the site, not exactly adequately conveying the message of what was happening there. Besides, it was Tuareg—hard to pull out the facts from hyperbole.

When Caro and I arrived, Tuareg and Jim were pacing about the quarry. Large black felt tarps dotted the desert floor every dozen feet, stretching north and south. I ambled up to Jim. “Dude,” he said in a low voice, telling me everything I needed to know in a single word. “This is not the Playa Pulpos that we saw two years ago.” Everyone gathered to follow as Tuareg walked from tarp to tarp, rolling each one backward. My mouth fell open as I absorbed the fact that every tarp covered at least one complete whale skeleton, and sometimes several on top of one another. Every black tarp, dozens spread up and down the road-cut quarry, demarcated a whale skeleton. The sheer density of complete skeletons outstripped everything I thought that I knew about how whales get preserved as fossils.

The skeletons, some thirty feet long, were almost all complete in a way that fossil whales hardly ever are, nose to tail. Many looked as if the creature had died in place, carefully turned on its back, and then been pressed flat over geologic time, like a preserved flower. Skulls were easy to spot, their triangular projections and bowed jawbones at the end of a trail of bricklike vertebrae. Rib cages collapsed toward tails, like gigantic Slinkys. In many skeletons, the ribs were still adorned with shoulder blades connected to arms and even finger bones. The fossil whales at this site were jaw-droppingly complete. And it made no sense that there were so many, so close together. I couldn’t think of any other field site of fossil whales like it.

I was stunned. Tuareg gabbed away with a positively gleeful Caro and her students. I walked over to where Jim stood at the south end of the quarry, taking photos and rubbing sediment between his fingers. We silently watched the sun slipping over the horizon, evening cloud banks bringing a cool wind. In the distance, a single round peak—El Morro, a weathered mound of igneous rock—capped the view.

“It’s over,” Jim said, flatly. I looked north and south across the entire quarry, more than a football field in length. I knew exactly what he meant: anything we had thought about doing needed to make room for this site and the several dozen skeletons that stretched up and down the hill in each direction. Measuring the stratigraphic columns across the Caldera Basin, slotting in all of the fossils we already knew about, deciphering that geologic map full of faults—it all needed to wait. My hours and hours of planning had focused on a sure thing, returning with bags of rock samples and with notebooks full of the makings of promised papers. Entire whale skeletons were not part of that plan, certainly not dozens of them.

I breathed in, anxious and unsure. I was frustrated with myself for not listening to Tuareg more carefully earlier on, paralyzed by the enormity of the scene in front of me. At the same time, part of me recognized that the scope of the site, with its dozens of perfect whale skeletons, was undeniably significant—and I had an open invitation to be one of the first ones to study a place like nowhere else, as far as I knew, on the planet. It was vexing and tantalizing; it was a kind of Pandora’s box, and we’d just seen it crack open.

“I know,” I said. “What are we going to do?”

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