Updated at 5:16 p.m. on July 5, 2019
Imagine you’re a baby mammoth. It’s 1.4 million years before the present day, in the middle of January, and you haven’t seen the sun in weeks. All around you, the Yukon tundra stretches into miles and miles of nothingness. Suddenly, a shape hurtles out of the darkness. And as you turn to meet your killer, you come face to face with … a hyena?
Since the first hyena fossil was identified in the Americas nearly a century ago, scientists have suspected that an extinct species of hyena, Chasmaporthetes ossifragus, must have traveled over the Bering Land Bridge from Siberia. But they never had definitive proof, until Jack Tseng, a paleontologist at the University at Buffalo, examined two mystery fossils that had sat in museum drawers for 40 years. Tseng knows a hyena tooth when he sees one, and he immediately picked up on the triple cusps and pyramidal shape of the third premolar. It took him only half a day to confidently identify the specimens as Chasmaporthetes.
Those two fossilized teeth just so happen to be the first to have been found in the Yukon, and in a new paper, Tseng and his co-authors peg them to be about 1.4 million years old. That means their owner, or owners, likely would have trotted around the same frozen landscapes as giant steppe mammoths and saber-toothed cats.
Hyenas are more familiar today as creatures of the savanna, but on some level, they make sense as Arctic inhabitants, living among large, trunked mammals and big cats, just as modern hyenas live among elephants and lions. “It’s really easy for us to sort of fall into a trap of thinking that these habitats were a lot like the African Serengeti,” says Grant Zazula, the Canadian government’s official Yukon paleontologist and a co-author of the paper. “And in some ways, they were.” After all, the desert and the tundra are both extreme, inhospitable climates, with no forests for big herbivores to hide in. Still, the Yukon during the Pleistocene era was dark four months of the year and very cold. Even though modern-day packs hunt at night, hyenas living in Ice Age Canada would still have depended on some very different adaptations—for a start, some thicker, lighter-colored fur would have been in order.
Based on other specimens collected in the past century, scientists know that Chasmaporthetes had longer, more evenly proportioned legs than modern-day hyenas, along with a shallower skull, which would have made for faster, more sustained running and a wolflike appearance. According to Julie Meachen, a paleontologist at Des Moines University, the hyenas would have hunted and scavenged on animals such as musk oxen and caribou in the Arctic tundra. They might also have chowed down on bison and horses in refugia between the glaciers, where things were relatively temperate and “a little more vegetated.”
Overall, “it would not have been a very comfortable life,” Tseng says.
Paleontologists don’t yet know how long Chasmaporthetes hung around in the Arctic. Meachen says the journey from Siberia to Florida, where other fossils have been found, would have taken at least several generations. But “it’s unknown whether this individual was just passing through, or whether it actually made its home” in the Arctic, she says. Scientists would know for sure only if they found a continuous fossil record in the region.
But such continuity would be hard to establish. Chasmaporthetes fossils in general are not as widespread as, say, Pleistocene-era bison, both because the hyenas themselves were not very densely populated and because glaciers can disrupt these records. The icy behemoths can act like bulldozers, churning up the rock and dirt and bones beneath them as they push along, explains Leigha Lynch, a molecular paleontologist at Washington University in St. Louis who was not involved in the study. When glaciers expand and retreat over centuries, that process can leave the terrain unrecognizable. “That’s the whole Pleistocene,” Lynch says. “It’s just one cycle of that after the other after the other.” (That said, glaciers and permafrost do have the added benefit of preserving flesh and hair, not just bones. As Tseng put it, “I’m hoping maybe one day some of the Siberian permafrost will reveal an Ice Age hyena.”)
Scientists think that plenty of other species made their way from Asia to the Americas, and vice versa, through the Arctic, but they still haven’t found—or, perhaps, identified—fossilized proof. “This is one of the few instances where we have unambiguous evidence,” Tseng says. So given that significance, why did the fossils sit around in a museum for four decades before Tseng came along to identify them?
The two teeth were first uncovered in 1973 and 1977.* Soon after, a paleontologist named Brenda Beebe wrote that she thought the specimens belonged to a different species of hyena. Beebe never published her findings, but she did send a manuscript to another paleontologist, Björn Kurtén. (Both Beebe and Kurtén have since died.) A few years ago, one of Kurtén’s former students, Lars Werdelin (who is also an author on the new paper), dug up the manuscript among Kurtén’s notes. He scanned it and sent it to Tseng, who got in touch with Zazula, who figured out that the teeth were being stored at the Canadian Museum of Nature.
After more than 40 years, all it took for Tseng to confirm that the fossils were Chasmaporthetes was a six-hour drive from Buffalo to Ottawa, a few hours of handling and photographing the fossils, and another six-hour drive back. He wrote the paper when he got home.
Meachen, who reviewed the new paper, says it’s “pretty basic” in that it doesn’t do much beyond describe the fossils at hand and offer a probable identification. A common problem with paleontology studies is that authors often draw sweeping conclusions from just a handful of bones or teeth, Lynch points out. “I really appreciated that the authors were very conservative in saying, ‘We tentatively assign it to this species, but we recognize that we have two teeth,’” she says.
The delay between the discovery and description of the Arctic Chasmaporthetes fossils is pretty standard for paleontology, a product of the way paleontological data are collected and how researchers organize their time. Zazula told me that his team can collect almost 10,000 specimens from Yukon sites in any given summer. That’s way too many fossils for them to get through immediately, and not every expedition team includes a hyena specialist, so the team catalogs them on a basic level and stores them until someone comes along to see them. Even the first known fossils of Chasmaporthetes, unearthed between 1901 and 1904, weren’t formally described until nearly 20 years later. “It’s pretty common in paleontology” for specimens to be found and not reported on, Meachen says. “I would love for it to be a systematic experience where people are like, ‘I’m going to go through this whole collection and describe everything that’s not described,’ but that’s never how it works.”
Once the right specialist gets around to looking at the right fossil, identification can often be as immediate as Tseng’s quick assessment of the Chasmaporthetes specimens. Meachen, who is an expert in Plesitocene-era cats and canines, told me, “I can do the same thing, and I can do it with teeth or I can do it with postcranial bones … It just depends on how much experience you have.”
If you’re a paleontologist, waiting a few decades to learn from new discoveries might seem trivial. “To think of hyenas being a major part of that system is so fantastic to most of us. But it’s also not that long ago. It’s geologically yesterday!” Zazula said. “A million years ago is nothing.”