Nick Pyenson, a National Geographic Explorer and author of Spying on Whales, thinks of himself as a whale detective. As a paleontologist he spends his time travelling the world examining whale bones in places as far afield as Chile’s Atacama Desert. The fossils help reveal the whale’s deep history, from extinct species that originally lived on land to today’s cetaceans. And by knowing their past we can help ensure that these magnificent creatures survive the many threats they face in today’s world.

When National Geographic caught up with Pyenson in Washington D.C., where he is Curator of Fossil Marine Mammals at the Smithsonian Institution, he explained how one ancient species of whale looked more like a dog than a marine creature, what he discovered when he spent time on an Icelandic whaling vessel, and how climate change is creating both winners and losers for whales.

Say whale and we think of a giant, oceanic creature. But the earliest whales, I was amazed to discover, were land-dwelling creatures the size of a German Shepherd. Tell us about Pakicetus and how it turned into a present-day whale.

That’s one of the most interesting aspects of the deep history of whales; they haven’t always been in the water. And that’s part of why it’s so exciting as an evolutionary biologist to have access to the fossil record, which tells us about the transformations that happened in their anatomy to go from living on land to living in the sea.

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Pakicetus is a species of early whale that has only been known since the eighties. Anatomists going back to 19th century Britain knew that whales were mammals and probably most closely related to hooved animals. But it is only in the last 40 years that we’ve found out that whales had ancestors that lived on land, with four weight-bearing limbs and elongated skulls that for all the world looked more or less like a dog.

Pakicetus fits into the bestiary of these early whales that are experimenting with various ecological modes. It may have looked more like a dog or a wolf—others looked more like otters or sea lions—but all these variations ended extinct. Those branches begat nothing, but there was one that did beget the whales we have today, and those were the ones that went fully aquatic, divorcing themselves from the land. That one branch then radiated into the 80-odd species of cetaceans we see today. Not just the big ones. Dolphins and porpoises all descend from that ancestral whale that went back to the water full time.

The other thing that jumped out at me was your assertion that whales have “cultures” and that these are based on their amazing ability to echolocate. Unpack the connection for us.

Echolocation isn’t related to culture. We can probably think of it best as a sensory system just like any other, whether smell, hearing, or vision. It’s the way one group of whales predominantly navigates under water and a useful way to communicate through a series of clicks. There’s a wide variety of sounds that whales can emit from the anatomical apparatus that gives them echolocation: a complex set of sinuses, muscles and a big, fatty mass that sits on top of their skulls and forms the dome-like structure we see in a lot of whales. Whether it’s a killer whale, porpoise, or sperm whale, they all have this fatty structure that serves as an acoustic lens.

The clicks and noises made from the forehead get focused by that fatty structure inside their heads, then emitted outside their bodies. It’s a very high frequency and bounces off the external environment, whether fish, subterranean canyons, or metal objects. It all gets relayed back to the echolocating whale which, we think—we don’t know for sure—picks it up in its jaw, which is connected via a fat pad to the skull. That anatomical arrangement, where sound is emitted from the forehead and received by the jaw, is how they see the world in sound.

Because it’s high frequency, they’re getting a lot of information about the environment very quickly. It’s very fine resolution. Whales are able to discriminate objects the size of household screws at a very large distance. It can also be very powerful. Sperm whales, which are the largest of the echolocating whales, have incredibly powerful sonar ability.

For as long as we’ve known about this, people have wondered, “What the heck are they saying?” The information content is very high, but without some context for knowing what they’re saying we don’t know what it means. It’s been a big mystery. They’re clearly having conversations, exchanging a lot of information. But what are they saying? That’s something that makes studying whales so much fun. There are so many questions we haven’t answered. And the more we have answered, the more there is to know.

How to Dive Like a Sperm Whale This massive marine mammal has all sorts of tricks for holding its breath for up to two hours at great depths.

You’ve dug up whale fossils all over the world, but one of the most exciting locations must have been Cerro Ballena, in Chile. You say the site is “an ecological detective story.” Uncover the case for us, Sherlock.

Cerro Ballena is about as unlikely a spot to find fossils as you can imagine. One lane of the Pan American Highway, which goes all the way from South America to Alaska, had been laid, cutting through a layer of rocks in the Atacama Desert. When they expanded it to two lanes to accommodate mining equipment, our local colleagues realized that the few whale bones we’d known about on the side walls of the cut actually represented much more. We ended up finding skeleton after skeleton of large baleen whales and many other marine animals.

The whales are spread out over about two British football fields. Some of them are piled on top of each other, others aren’t, but they’re all within a few meters of one another. Your first question is, “What is going on here?” And it wasn’t just whales. There are many other species of large marine animals, including seals, extinct dolphins, and even a species of sloth that had evolved aquatic adaptations.

Everything was consistent with algae blooms as the cause. These microscopic toxins create poisons, as we know today. We think it happened at Cerro Ballena because of the geology. The erosion of iron-rich sediments from the Andes to the coast created the right conditions for these toxic algae blooms to kill a variety of marine animals in the geologic past. That’s what makes it an ecological detective story; we had to infer that based on the evidence at hand.

You also spent some time knee deep in gore on an Icelandic whaling vessel sawing off the chins of whales. Why chins? And how did you feel working with the industry that brought whales to the brink of extinction?

Whaling has been a part of human culture for thousands of years and still goes on today. The U.S. is still a whaling nation and it happens in Alaska for many indigenous peoples, a fact that many people forget. It’s seen as part of culture for many First Nations. But by far the largest numbers of whales are killed by Japan, Iceland, and Norway, though the number is still far smaller than the number of whales killed by ships’ drag or net entanglement. Whaling gets a lot of attention because of the way we do it, chasing whales with harpoons off fishing vessels. But the indirect impacts of whales living on planet Earth in the age of the humans takes a far greater toll. Hundreds of thousands of whales are killed every year as compared to the few thousand killed by the whaling industry.

Japan calls its whaling scientific whaling. What happens in Iceland and Norway is commercial whaling and they regard what they do as no different from any other fishery, whether tuna or swordfish. Through a variety of circumstances we were allowed to go to one of the whaling stations in Iceland. When you have access to 20 people with flensing knives and equipment for pulling the carcass apart, you have the ability to investigate large-scale anatomy much better than ever before. So it was an important opportunity for us as scientists to answer the questions we had about the links between ecology and the animals’ anatomy.

For all the millions of whales that have been killed, very few have ever been looked at by anatomists in a detailed way. Lo and behold, we were lucky enough to find something unusual: the structure in the chins of whales. Using detective work, we discovered a sensory organ that coordinated the way whales can gulp-feed a lot of prey-laden water. This is the feeding style for the largest whales on the planet, like blue whales, fin, or humpback whales, so it turned out to be something pretty important.

The whaling industry had one surprising benefit: providing unique historic data about whales. Tell us about the British government’s Discovery Investigations from South Georgia and what they revealed about whales.

Whaling in the 20th century took a huge toll on whale populations. Fortunately, some of the whaling nations in the Southern Ocean had a system for documenting what they were doing. That may not be so surprising when you consider that it was an industry just like any other. To make money, you need to show the returns and by recording which whale was killed in which spot, how big it was, and what species, they essentially produced a tally of biodiversity in the world’s oceans in the 20th century.

The questions we have today about the conservation of these species is reliant on what the baselines were like before and during whaling in the 20th century. We have no real record aside from that, of just how many whales there were in the oceans; everything else is inference. The record keeping was done by the British through the Discovery Investigations. In some cases, they measured the whales, their girth, length, and width and, in some cases, estimated the weight. This gives us valuable information we wouldn’t otherwise have.

You write: “Whales aren’t my destination: They are a gateway to a journey of discovery across oceans and through time.” Bring it home for us, Nick, by explaining what you mean.

I study whales not just because they’re big or lead complex lives. All those facts are true, but when you ask scientific questions about how they are and where they came from, you realize there’s a lot we know but so much more we don’t. Scientists are drawn to mysteries as much as anybody, and when you consider that we don’t even know how many species of whales there are on the planet, we have a lot of work to do to understand the totality of facts about their lives. And the depth of their history can inform us about what’s going to happen to them in the future.

The fate of whales is not an easy thing to predict, though, because there are so many different ways that whales live. Some live in freshwater river systems, like the Yangtze River Dolphin, which went extinct in 2000. The Vaquita, which is endemic only to the Gulf of California, is being decimated as a side effect of rampant, illegal fishing for a fish called the totoaba, a large fish whose swim bladder fetches a lot of money on Asian markets.

A much larger species of whale, the grey whale, is winning as the world changes because their ecology is flexible. They migrate long distances and with the Arctic becoming free of sea ice in the summer, it would not be surprising to see grey whales migrate even farther around the world. There are already reports of grey whales far from where we usually know them, which is the North Pacific. We’ve also seen reports of grey whales in the Mediterranean or South Atlantic. So this highly migratory species is taking advantage of changes happening on the planet. Those are two compelling examples of whales living on planet Earth in the age of humans. Some may go extinct, others may become winners.

This interview was edited for length and clarity.