In case you haven’t heard of it, this show was a Planet Earth-style nature series set 5 million, 100 million, and 200 million years in the future. With the aid of questionable CGI, it imagined the sorts of creatures that might evolve on our planet long after we are gone. There were fish that developed powered flight, octopi that swung through the trees, elephant-sized tortoises, and gannets that evolved to swim like whales. It sent my imagination into overdrive. For a ten-year-old who longed to learn about every animal past and present, it might as well have been cocaine.

The Future is Wild, like other speculative evolution projects like After Man and All Yesterdays, are predicated on the idea that evolution is predictable. By looking at established evolutionary patterns, the show suggests, we can divine what might evolve in the future — maybe squid will end up on the evolutionary path that primates went on, for instance, or some crustaceans will evolve to be fish-like. It made for very fun television and was an effective way to teach viewers about evolution, but it was all just silly fun at the end of the day.

But perhaps such an approach may be more realistic than we might think. Because one time, a prominent entomologist predicted the existence of an animal that no one on earth thought existed.

And then scientists discovered it.

Richard D. Alexander was an evolutionary biologist who taught at the University of Michigan from 1957 until his retirement in 2000. Throughout his career he studied the ecology and evolution of everything from crickets to horses to humans. Few biologists have been so prolific or covered such a wide range of species and subjects.

One of his most notable contributions concerned a deceptively simple question: if evolution prioritizes survival of the fittest, why did some animals evolve to be social? His 1974 treatise aptly titled “The Evolution of Social Behavior” tried to answer this question, providing a general theory of social behavior that is still relevant today.

That whole paper is worth reading, but the most important section for our purposes is his discussion of eusocial organisms. Eusocial animals are those that live in complex social arrangements made up of a queen and a small group of drones that can reproduce alongside many sterile workers, like bees and ants. It is an unusual evolutionary strategy as it robs the vast majority of individuals of their ability to reproduce while ensuring a select few reproduce wildly, essentially turning the entire colony into one superorganism.

Previous researchers argued that this queen-worker arrangement evolved due to a strange quirk of some insects’ genetics.1 Alexander’s argument was much simpler — eusociality is just a more advanced version of social behavior, where parents choose which of their offspring get to reproduce, as bees do when they only feed certain offspring the “royal jelly” required to turn a larva into a queen. He believed it required no inherent genetic quirk to be possible.

Other researchers, however, challenged this view with a simple question: if eusociality is just advanced parenting, why aren’t there any eusocial vertebrates? After all, far more mammals and birds take on active parental roles than insects. If Alexander is right, why don’t we have queen dogs or worker parrots?

Shortly after publishing his 1974 paper, Alexander embarked on a lecture series across the country to discuss his research. In it, he took his critics’ feedback of his eusociality theory, and instead of refuting it, asked himself a simple question:

What would a eusocial vertebrate look like?

As the National Center for Science Education described, Alexander outlined a 12-part model of what this hypothetical eusocial vertebrate would look like. It would need to have a nest with many of the same characteristics of a termite or bee nest. Its nest needed to be safe, so that predators couldn’t destroy it. It would need to be expandable, so that it could improve as a colony grew. It would need to be near an abundance of food, too, and that food needed to be obtained with little risk to the workers — otherwise competition would arise between workers for food.

He concluded that no tree is large enough to host such a nest of vertebrates, so it would have to be underground, specifically in hard clay where predators could not easily dig up the nest. He then concluded that this animal would likely be a mammal, and more specifically a rodent, which are already evolved for burrowing underground. He supposed it would have to eat roots and tubers, as those are nutrient-rich and replenish quickly enough to be eaten perpetually by a large colony of rodents.

These eusocial rodents would also likely be eaten by snakes or other snake-like predators, but these predators could be deterred through the heroic sacrifice of a non-reproductive individual. The rodents would likely live in tropical areas with wet and dry seasons, because plants there regularly store nutrients in large roots to get through the dry season. Between the requirements for seasonality and the hard clay, he then concluded that this animal would have to live in open woodland or scrub in Africa.

An African rodent that lives in large underground colonies and survives on roots and tubers. Maybe you see where this is going.

After one of Alexander’s lectures at Northern Arizona University at Flagstaff, a young mammalogist named Terry Vaughn approached him and told him that there already is an animal that perfectly fits this description: the naked mole rat.

This nearly hairless rodent, perhaps best known to my generation as Kim Possible’s sidekick, is a colonial breeder that lives in large underground colonies in the Horn of Africa and subsists on tubers. When Terry Vaughn told Alexander about this animal, he encouraged him to get in touch with Jennifer Jarvis, a South African biologist who studied mole-rats. Jarvis confirmed that they matches Alexander’s description, but told him that nothing was known about their social behavior.

You have to wonder if this conversation had an effect on Jarvis, because just five years later, she published the results of her laboratory experiments on a colony of naked mole rats. These results confirmed that, among a colony of mole rats forty-strong, only one female was responsible for all reproduction. Naked mole rats had a queen. They were eusocial. Richard Alexander had successfully predicted the existence of an animal that no one on the planet knew existed.

I would have given anything to see his reaction.

What makes his prediction particularly interesting is that naked mole-rats eusociality is very different from that of insects. In insects, castes are typically permanent. Naked mole-rats, meanwhile, are flexible. If a queen dies, there is an immediate power struggle between the colony’s other non-reproductive females to become the next queen, sometimes even resulting in a colony briefly having multiple queens at the same time. This struggle can get violent, and pup survival tends to drop immediately after a queen’s death. None of this messiness happens in insects — in bees, sterile workers simply choose a new larva to become their queen and feed it royal jelly. In other words, naked mole-rats invented a brand-new form of eusociality entirely unique to mammals.

Naked mole-rats became one of Alexander’s favorite study species almost immediately. Jarvis and Alexander became frequent collaborators and published several papers about naked mole-rats before co-authoring the 1991 book The Biology of the Naked Mole-Rat. Jarvis also discovered that the Damaraland mole-rat, a much furrier and cuter cousin of the naked mole-rat, is also eusocial. Alexander had predicted not one, but two animals’ existences.

On one level, perhaps it’s dumb luck that Alexander was right. Had an especially virulent disease or changing climate wiped out naked mole rats a few thousand years ago, we would never have known his prediction was accurate. But Alexander’s prediction demonstrates two things: one, that Richard Alexander had a profound understanding of the way evolution works, and two, that evolutionary forces are consistent enough that it is sometimes possible to predict what they will do. It’s a remarkable illustration of how consistent and powerful evolution can be.

It’s also a reminder that evolution can head in directions that most people don’t expect. Most scientists thought that eusociality was not just absent in mammals, but impossible. Then, naked mole-rats proved that evolution is not so limited.

Perhaps the wacky animals of The Future is Wild will come into existence one day. But evolution could just as easily head in even more surprising directions — if we could peer millions of years into the future and see what today’s animals will become, I would bet that they would be far more original and incredible than what our imaginations are capable of creating.

What to make of this extinction? Told in a vacuum like this, it’s a sad story — a once great and prosperous animal driven to extinction by settlers. But brown bears aren’t extinct in general, mind you. The California brown bear is just a subspecies, a slice of a real species. Yes, it’s sad that California doesn’t have brown bears anymore. But does it really matter when you can drive a few states over to see them in Yellowstone?

If you’ve taken high school biology, you’re probably familiar with the simplified definition of the term “species”: if two organisms can produce viable offspring together, they are members of the same species. This is called the biological species concept, and while it is arbitrary (lots of animals that we call different species can produce viable offspring together) and often untestable (how do you know whether two animals that never meet could or could not breed?), at least it’s something. There is no equivalent definition of subspecies — even the great evolutionary biologist Ernst Mayr, who created the biological species concept, once quipped that “subspecies [is] not a concept of evolutionary biology but simply a handle of convenience for the clerical work of the museum curator.”

Because of this lack of a consistent definition, it can be hard to convince people that the extinction of a subspecies matters. But no matter how arbitrary a subspecies might be, its extinction still means the loss of a special and irreplaceable group of animals.

Take another extinct bear, this one native to Africa.

The Atlas bear (Ursos arctos crowtheri) was a subspecies of brown bear that was once found in the Atlas Mountains of northern Africa stretching from Morocco to Libya. It was smaller than other brown bears, about the size of most black bears. Nonetheless, it was considered a frightening beast by the Romans. The geographer Herodotus invoked the Atlas bear to described the region around Libya as “full of wild beasts. In that country are the huge snakes and the lions, and the elephants and bears and asps.”

When exactly the Atlas bear went extinct is a matter of some debate — while some controversial accounts suggest it survived into the 19th century, most researchers suggest it went extinct some time in the 600-800s AD. Why they went extinct is equally hard to pin down. Perhaps it was a mixture of hunting, land use change, and an increasingly extractive economy in northern Africa as the region swapped hands between Carthage, Rome, and Byzantium, exacerbated by a dramatic climatic shift in the mid-500s. But that is only a guess, and we will likely never know what ultimately doomed the Atlas bear. All we can say for sure is that, at some point between the fall of Rome and today, the Atlas bear went extinct.

What was lost when the last Atlas bear died? We know that it was smaller than most brown bears, built stouter and thicker with shorter claws. But until recently, we had little idea of what made this animal special beyond that.

The first hint of an answer came in 2008, when a group of scientists sequenced the genome of a handful of Atlas bear fossils. Previous work had found that brown bear DNA was pretty consistent across populations since the latter part of the last Ice Age, indicating that the many global populations of brown bears were relatively similar to one another. This study, however, found that Atlas bears bucked that trend. Their DNA was radically different from any other known population of brown bears — as the authors write, “a significant portion…of the diversity of the brown bear was lost with the extinction of the Atlas brown bear.”

But even with their enormous genetic difference, scientists weren’t sure how Atlas bears differed from other brown bears ecologically. Then, this June, a group of scientists took a look at what they ate.

These scientists, led by paleontologist Aurora Grandal-d’Anglade, examined the bear's diet through the chemical makeup of the collagen in its bones. They looked at the ratio of different forms of nitrogen, known as isotopes, in the fossils, which can indicate where an animal sits on the food chain. Since nitrogen-15 accumulates in animal tissue, the more animals a given creature eats, the more nitrogen-15 will be in its bones. These scientists found that big cats in the Atlas mountains had a nitrogen-15 level around 8%, while herbivorous ungulate levels ranged from 4 to 7%. The bear, meanwhile, had a nitrogen-15 level as low as 3%.

In other words, Atlas bears were herbivores. They were the brown bear equivalent of giant pandas, gnawing on leaves and fruits while their relatives hunted deer and fished for salmon.

On one level, perhaps this finding isn’t too absurd. All brown bears are generalists and consume a wide variety of foods, including fruits, tubers, and other vegetation, but they typically eat meat, too (in Yellowstone, for example, meat comprises around 50% a brown bear’s diet). Grandal-d’Anglade and her team suggest that Atlas bears shifted their diets towards plants thanks to the presence of Barbary lions (Panthera leo leo) and Barbary leopards (Panthera pardus pardus), two other predator subspecies native to the Atlas Mountains that are now extinct. Competing for prey with these two big cats was clearly harder than simply becoming vegetarian.

But this explanation does not minimize the fact that no other brown bear population is purely herbivorous, even those that live around other large carnivores. When we lost the Atlas bear, we lost a brown bear unlike any other on Earth. In fact, one of the few brown bear populations that approached this level of vegetarianism was the California brown bear, whose diet was 90% vegetation before colonization.

These two different bears on opposite ends of the world, driven to extinction through conflict with humans, represented a completely novel way to be a brown bear. When these subspecies went extinct, the entire species shrank, not just in range or population but in possibility. The brown bear was flattened into a single type that could never represent the entire species as it once was.

This is what we lose when we lose a subspecies: an entire way of being alive that we will never see again.

The turn of the century was a rare period of economic stagnation for the Massachusetts island. A century prior, it was a major player in the whaling industry, extracting thousands of gallons of whale oil every year to sell to industry-rich cities like New York and London. A century later, it had firmly established itself as the premier vacation destination for the mega-wealthy. But for several decades in between, Nantucket was depopulated, underdeveloped, and isolated. Much of its income was from farming and fishing. And into this environment, in 1890, someone decided to introduce a few prairie dogs, creating one of the surprising cases of an otherwise benign animal causing chaos in a new environment.

It’s not clear who did this, or why, though it may have been due to the absence of game animals on the island — as conservation biologist Sarah Bois noted in her account of the prairie dogs of Nantucket, one 1891 letter to the local paper The Inquirer and Mirror supported the new animals because “we have little or nothing, but waste lands about the island. What harm can arise from any of these innocent little animals?”

Native mammals are notably absent on Nantucket. Foxes, skunks, raccoons, coyotes, and many other New England mammals do not make the swim to Nantucket. So it makes sense, in a 19th century sort of way, that introducing prairie dogs would be beneficial for “rounding out” the ecosystem and making the island better for hunting. As their numbers grew, the prairie dogs clearly found the coastal sandy plains and heathlands to be an acceptable substitute for shortgrass prairie.

In the North American interior, few animals are as ecologically important as prairie dogs. They form massive colonies that can number well over 1000 animals which, by constantly consuming larger plants, create a perpetually sparse habitat that serves as nesting grounds for rare species like Mountain Plovers. Their burrows also serve as shelter and nesting habitat for burrowing owls, rattlesnakes, and cottontails. They also provide an important food source for hawks and eagles as well as more specialized predators like badgers and black-footed ferrets.

But while Nantucket has plenty of raptors, it lacks badgers and ferrets. Without these predators, the prairie dog population soon exploded. Clinton Hart Merriam, father of American mammalogy and close friend of Theodore Roosevelt, received correspondence from one Nantucket resident who described the rodents as “a dangerous pest and nuisance, destroying crops and fields.” Bois suspects that their burrows may have injured local livestock and horses, too, as is commonplace in their native range.

So, the island’s Board of Selectmen got to work. In 1896, the board drafted up legislation for a prairie dog bounty at 10 cents a head, which was approved at a town meeting. The meeting minutes note that “some sharp criticisms for the parties introducing [the prairie dogs to the island] were offered.” Sadly, the exact insults lobbied at the prairie dog introducers have been lost to time.

The bounty went into effect, but did very little to stymie the prairie dogs’ population growth. By 1899, Merriam noted that the island hosted four large colonies of over 200 animals each and many more smaller colonies and pairs scattered throughout the island — a total of around 1000 animals. Clearly, something more needed to be done.

What’s interesting is that, at exactly the same time as this prairie dog war played out on Nantucket, another invasive species was wreaking havoc on a tiny island off its coast. It inspired no arguments at town meetings nor did it result in any allocated funding. But it mattered for one rare animal in particular: the region’s only endemic mammal.

Meet the beach vole.

Depending on who you ask, the beach vole is either a subspecies of meadow vole or its very own species. It’s a small rodent that lives on a tiny, 250-acre island just west of Nantucket called Muskeget Island. Its beaches are a major breeding site for gray seals as well as waterbirds like piping plovers and roseate terns, while its uplands, rising an astonishing 14 feet, are dominated by beach grasses, poison ivy, and a handful of hardy flowers. This latter zone is the domain of the beach vole. They live among the sparse vegetation, eating seeds, grasses, and insects and breeding in shallow burrows.

For thousands of years, beach voles lived on this island in relative peace, surviving attacks by visiting raptors unscathed. According to Gerrit Smith Miller Jr., then-assistant curator of mammals at the Smithsonian Museum, beach voles were abundant on Muskeget as late as 1869. Then, according to Miller, the island’s lifesaving station burned down in the 1880s, releasing a population of feral cats onto the island. There, they made short work of the island’s beach voles. By 1891, he wrote, “the animals disappeared completely.”

But while the voles went extinct on Muskeget, they didn’t disappear completely. Some time between 1887 and 1890, a spit of sand on the south end of Muskeget was severed from the island by the ocean currents, creating a new, smaller island known as South Point Island. Beach voles survived here since the channel of water kept cats from reaching the island. Thanks to a tiny quirk of geology, the voles had another chance.

Not long after they devoured the entire Muskeget beach vole population, the island’s cat colony died out in 1893. It is unclear if this is due to lack of food, harsh winters, or purposeful extirpation. The voles, meanwhile, eked out a living on South Point. That summer, Miller, alongside his colleagus Outram Bangs and Charles Batchelder, went to South Point Island in order to study the voles. But while there, they decided to do something about their elimination from the main island. They took 26 voles from South Point, brought them over to Muskeget, and released them.

It was the nick of time. A mere two years later, Miller noted that the colony on South Point Island died out. Today, South Point doesn’t even exist. It washed away beneath the waves around Nantucket. The natural flow of the tides protected the vole just long enough for it to be saved by Miller, Bangs, and Batchelder. Today, the beach vole still thrives on Muskeget.

The townsfolk of Nantucket, meanwhile, were unaware of the drama playing out on Muskeget Island. They were much more concerned about the prairie dog problem. Some time in 1899 or 1900, the island had had enough, and they created a Prairie Dog Elimination Committee at town meeting that year and funded it to the tune of $350 — the equivalent of around $14,000 in today’s money. The bounty system was a failure, so the committee settled on a different extermination technique: a deadly poison called carbon disulfide. The committee had people soak rags in the toxin and scatter them around the largest prairie dog colonies. This worked. In February 1900, one resident wrote that “now there is not a dog left to tell the tale.”

Today, the brief reign of the Nantucket prairie dogs is scarcely remembered. But had they not been perceived as a pest by the locals, they probably would have been allowed to thrive on the island like gray squirrels and eastern cottontails, both of which are not native to Nantucket. As Sarah Bois says, “if it weren’t for deep burrows and wide openings to said burrows, our high school mascot may be the prairie dogs instead of the Whalers.”

Now don’t get me wrong, the whalers are a good team name, but the days of whaling are over. Prairie dogs are cute, but they’re borrowed from elsewhere. So if we’re in the business of choosing a new mascot for Nantucket High School, why not something that is unique to the region?

I think “Go Beach Voles!” has a nice ring to it.

But within this great man-made city, Townsend writes, one of the most impressive sights would have been the birds.

In large, finely wrought wooden cages, the brightest birds from the jungles in the east and south fluttered and sang — quetzal birds and parrots, flamingos and tufted ducks, parakeets and pheasants — too many kinds to count. As the birds flew quickly in and out of the foliage, the colors of their wings glinted in the evening light, like flashes of magic, the result of some spell, just like in the stories.

This image does not jive with how most modern people talk about the Aztecs. To many, they were a brutal civilization, whose jaguar warriors tore out their enemies’ hearts and whose priests practiced human sacrifice. Such a depiction, however, obscures a diverse, complex society with a rich culture — heroic princesses, brilliant engineers, shrewd diplomats, gay emperors, poets and philosophers who rivalled any in Europe, and a rich spiritual tradition beyond human sacrifice.

They also really, really loved birds. The Aztecs worshipped gods like Huitzilopochtli, symbolized by a hummingbird. They hunted pelicans, herons, ducks and other waterbirds for food. They used feathers to decorate clothes, shields, and jewelery. The imperial dynasty maintained an extensive zoo filled with macaws, cotingas, spoonbills, raptors, and other rare birds.

Birds are even key to the founding of Tenochtitlan. According to their tradition, the Mexica (one of the three founding cultures of the Triple Alliance, also known as the Aztec Empire) were told by their god Huitzilopochtli to found a city where they saw “an eagle with a snake in its beak perched atop a prickly pear.” When the Mexica witnessed exactly this sign while hiding on a marshy island in Lake Texcoco, they decided to found their capital city there.

And alongside their reverence, there is evidence to suggest the Aztecs might have introduced an entirely new species of bird to their homeland.

In the aftermath of European colonization, Aztec and Spanish historians began compiling histories of the Aztec Empire. The most famous of these histories is the so-called Florentine Codex, compiled by Spanish friar Bernardino de Sahagún between 1545 and 1590. The codex is made up of 12 books that cover everything from Aztec gods and religion to mercantile practices to ethics and philosophy.

Book 11 covers natural history. In this book, Sahagún compiles a species-by-species account of the important animals within Aztec culture in incredible specificity and detail, to the point where it includes two different species of grackles. One is referred to as the tzanatl. It was black with a curved beak, about the size of a thrush, caused great damage to the maize harvest, and was “not good to eat.” This likely referred to the slender-billed grackle, a now-extinct species native to the valley of Mexico. Based on the tone of the description, it seems unlikely that the Aztecs would have mourned their passing.

It’s the other grackle that gets more attention in the codex: the teotzanatl, which we call the great-tailed grackle. It is described in much more flattering terms — the male has “a very fine black color” and a “long, chiseled tail; it is a good singer.” Fittingly, the name teotzanatl means “precious grackle,” which they got because they are not originally found in the Valley of Mexico — “they came to these parts not too many years ago, when Ahuitzotl was lord.”

Ahuitzotl was the eighth emperor of the Triple Alliance, ruling from 1486 to 1502, shortly before colonization. He is perhaps best known for his wars with groups like the Mixtec and Zapotec on the Pacific coast that extended Triple Alliance power as far south as modern-day Guatemala. He also appeared to have a particular fondness for the great-tailed grackle. These grackles were originally only found in the coastal lowlands, but according to the codex, the teotzanatl “came to these regions of Mexico by his [Ahuitzotl’s] order,” imported from the provinces of Cuextlan and Totonacapan on the Gulf coast.

The practice of importing exotic birds might seem like a strangely modern idea, but the Aztecs had a lot of captive birds in their zoos and gardens. Nearly all of these birds were transported to Tenochtitlan from the tropical lowlands, which had far more avian biodiversity than the Mexican highlands, particularly among colorful birds. Some of these birds were imported by long-distance merchants called pochteca, while others were given to the city as a form of tax by conquered provinces.

Some were even poached. The Triple Alliance were home to an elite crew of pochteca that snuck into the territory of unconquered peoples to steal rare goods, including birds. In the Florentine Codex, Sahagún describes how these pochteca would cut their hair, adopt a new dress, and learn a new language to go undercover beyond Aztec borders, where they faced death if they were caught. They had special techniques to capture birds, too. Sahagún describes how pochteca captured blue cotingas, whose colors were so rich and feathers so delicate that the pochtecas risked breaking the feathers and staining the plumage if they simply grabbed them, by “grasp[ing] a handful of green grass; with it they seized the bird.”

Regardless of how the great-tailed grackles were originally captured, they were soon brought several hundred miles inland and upslope to Tenochtitlan, where Ahuitzotl ordered for them to be released. Then, the residents of the city were instructed to feed them and do them no harm. According to the codex, “if anyone stoned them, they chided one another; the common folk said to one another, ‘’What are you doing over there? Do not shout at, do not stone the lord’s birds!”

Soon, the teotzanatls spread beyond Ahuitzotl’s control. “When they multiplied, they scattered, they traveled everywhere, they ate everywhere,” the Codex reads. These grackles established themselves throughout Tenochtitlan and the surrounding countryside. When the Spanish came and christened the old capital as Mexico City, the grackles remained. The great-tailed grackles that live in Mexico City today are very likely the descendants of those individuals introduced by Ahuitzotl 600 years ago.

The idea that Ahuitzotl was responsible for establishing the modern population of great-tailed grackles in Mexico City was first proposed by UC Santa Barbara biologist Paul Haemig in 1978. His paper was controversial for all the reasons you expect — us Westerners have been fed the idea that Indigenous Americans were primitive people that lived in harmony with nature for our whole lives, so the idea of an Indigenous Empire exercising their power over nature in such a dramatic fashion was too much for some.

The original and perhaps most significant critics have been Van Remsen and Steven Cardiff, two ornithologists from Louisiana State University. In a paper covering range trends in guans, the two men take a passing shot at the grackle introduction story as unconvincing — they note that other lowland birds like American bitterns, ruddy ducks, and marsh wrens have isolated populations on the Mexican plateau, and they dismiss the codex as “a friar’s 1577 collection of animal stories told to him by Aztec informants.” Remsen and Cardiff “regard such folklore with distrust,” saying that their experience with South American Indigenous people “is sprinkled with cases of amusing, but obviously erroneous, explanations of past and present natural phenomena.”

If we can momentarily set aside the racist overtones of the second point for a moment to address their first point, the Florentine Codex actually distinguishes between the great-tailed grackles and those other birds with disjunct ranges. The American bittern is described in the codex under many Nahuatl names, including atenponaztli, which refers to a two-toned drum that the Aztecs used as a musical instrument —and anyone who has heard an American bittern’s dramatic “gunk-a-lunk” display knows exactly why this name is so fitting. This bird, however, is not described as having been imported by a past emperor.

As to the second point, these stories were not folklore. As Haemig later argued in a follow-up paper, the Florentine Codex was peer-reviewed, thoroughly researched, and based on the consistently accurate information. But perhaps more importantly, Ahuitzotl was not some semi-mythical figure in Mexican history — his reign ended only 43 years before Sahagún began work on the Florentine Codex. There were plenty of people alive who had witnessed Ahuitzotl’s introduction of the teotzanatls. Referring to the Codex as “folklore” and “a collection of animal stories” is like referring to a Vietnam veteran’s war stories as “an epic tale from a distant Age of Heroes.”

Then, of course, there’s Remsen and Cardiff’s line about South American Indigenous people. Conflating Indigenous South Americans of the 20th century with Indigenous Mexicans of the 16th century is stupid at best and racist at worst (no one would say they got lied to while on vacation in Scotland and therefore conclude a 15th century Russian text must not be reliable). But Remsen and Cardiff’s rejection of a very common phenomenon — a group of people importing and releasing exotic birds in a new location and those birds subsequently establishing a population there — simply because it is done by a pre-Columbian civilization speaks to how little agency Indigenous people are given in Western thought.

While Indigenous people are often viewed by Europeans and white colonizers are living in harmony with nature, such an idea perpetuates a harmful, racist myth of an insignificant, unchanging culture that crumpled when it met modernity. But Indigenous people dramatically shaped their environment before colonization. They constructed large cities in Mexico, the Andes, and the Mississippi River Valley. They stewarded and harvested entire forests, changing their range and composition to suit their needs. Their burning created the Great Plains. Their tree planting created the Amazon.

One of the reasons that this myth is promulgated is to suggest that the postcolonial genocide of Indigenous people was the inevitable result of Europeans’ arrival, not something that was intentional. But it was intentional, driven by a mixture of greed, pride, religious fervor, and eventually scientific racism. It just makes us feel better to say it was inevitable after the fact.

It’s also important to note that this genocide was not successful. Indigenous people still exist today and still steward their lands. Even the Aztecs, viewed as fallen empire, were not completely defeated by the Spanish — it would be many decades before the Aztec royal line lost influence, and many cultural staples of the civilization still figure prominently in modern Mexico. Aspects of Mexican food, art, and culture can all be tied back to the Triple Alliance. Even Nahuatl, the language of the Aztecs, is still spoken by around 1.7 million people today worldwide — about as many as speak Latvian.

And great-tailed grackles still fly over Mexico City. No matter what Europeans did to the former capital, they could not erase all signs of the Aztec Empire’s former glory. The great-tailed grackle is Ahuitzotl’s indelible fingerprint, proof that this great city was once called Tenochtitlan.

That was a quote from then-Governor of Virginia Thomas Jefferson, who believed that the Peaks of Otter, a trio of peaks within the Blue Ridge Mountains in Virginia, were the tallest mountains on the continent. If you hadn’t heard of them, that is perhaps a good clue to the fact that he was wrong — indeed, they are not even the tallest peaks in Virginia.

Though the height of these mountains may not live up to Jefferson’s imagination, they are still spectacular in their own right, particularly in their biodiversity. Each summer, the buzzy song of the cerulean warbler rings down from the tree tops, while Canada warblers sing back from the understory. Flying squirrels scamper through the branches, risking attack by a hungry bobcat if they ever wander too low. More than 2,000 species of plants grow in the broader region, and the Peaks of Otter themselves are home to a variety of rare species like piratebush.

But in the leaf litter beneath all these organisms lives perhaps the rarest species of all: the Peaks of Otter salamander. Small and brown with brilliant flecks of gold running down its back, it is both adorable and beautiful. It is also entirely restricted to 45 square miles of forest surrounding the namesake peaks. It wasn’t until the 1950s that scientists recognized that this salamander even existed — and when they did, it set off one of the cattiest dramas in the history of herpetology.

In the mid-20th century, there was something of a herpetological gold rush in the Appalachians as scientists realized how many undiscovered salamanders lived there. Today, the Appalachians are often called the global hotspot of salamander diversity, but this is a relatively new designation. The Peaks of Otter Salamander’s genus Plethodon, for instance, included only six recognized species at the beginning of the 20th century. Today, that species count sits at 49.

As the number of salamanders grew, however, so did competition between herpetologists to describe them. The biologists M. Graham Netting and Myron B. Mittleman exemplify this well. The pair — one from the Carnegie Museum of Natural History and the other from Ohio University — each independently discovered the Plethodon richmondi, the ravine salamander, in West Virginia. When they each realized the other was planning on describing it, too, they began to argue over who deserved priority and had a falling out in 1938. They reconciled their differences, though, and opted to co-describe the species that same year. Then, ten years later, a Master’s student at Cornell University named Richard Hoffman sent them both specimens of an undescribed salamander from Virginia, and yet again, Netting and Mittleman couldn’t agree who should get to describe the species. They had another falling out, with poor young Richard Hoffman being carbon-copied on every nasty letter they sent each other. During this spat, Netting told Hoffman directly that he shouldn’t study salamanders, since too many people were already working in the field.

(As a side note, I cannot confirm this, but I sincerely hope that this Myron Mittleman is also the Myron Mittleman that got hospitalized at 16 after being bitten by his pet Gila monster).

Richard Hoffman is one of the three heroes in the Peaks of Otter salamander story. After being caught in the middle of the Netting-Mittleman drama, he had soured to herpetology, but he and his herpetologist friend Richard Highton, a biologist at the University of Maryland, continued to take salamander-finding field trips together. On one of these trips, Hoffman and Highton decided to look for a recently described population of salamanders along the Blue Ridge Parkway near the Peaks of Otter. This population had been discovered by snail biologist Leslie Hubricht (who also discovered the Iowa Pleistocene Snail) and described by herpetologist Gordon Thurow, who deemed the specimens to represent a population of Cheat Mountain salamander. Highton, however, had looked at the specimens, too, and he thought they might belong to an entirely new species.

These men are our three protagonists: Richard Hoffman, Richard Highton, and Gordon Thurow. On an October 1956 salamander-ing trip to follow up on Highton’s suspicions, he and Hoffman found the salamander that Thurow described in abundance near the Peaks of Otter. Highton went to great lengths to note that the location they found it was different than the one Thurow listed in his paper, since Thurow apparently mis-wrote where Hubrict had found the original salamander specimens. Hoffman and Highton agreed that the salamanders were not Cheat Mountain salamanders, but an entirely new species. Hoffman suggested the name Plethodon aureolus for them, and the two began preparing a manuscript for submission.

That November, while working on the paper, Highton learned that Thurow, who was also a medical doctor in the Army, was stationed at Fort Detrick, Maryland. Since this was not far from Highton’s home, Highton phoned Thurow and invited him and his wife for dinner. During the phone call, Highton informed Thurow, with what one can only imagine was a hint of gloating, that he and Hoffman had collected more specimens of the salamander and were planning on describing them as a new species. Highton also informed Thurow that he had mislabeled the type locality of the population. Despite Highton’s goading, Thurow and his wife accepted the invitation to dinner.

By December, Hoffman and Highton had completed their paper. Before publishing, the two men decided to donate their type specimens to the Smithsonian Institution. When Highton telephoned the museum, however, the curator told him that she already had type specimens for that salamander. They had been donated by Thurow.

It turned out that Thurow, upon hearing from Highton that he and Hoffman were planning on describing “his” salamander population as a new species, rushed down to the Peaks of Otter, collected some new specimens, and quickly wrote up a description of the species. He called it Plethodon hubrichti, after the snail biologist that had collected the original specimens. As Thurow wrote in his description, “thanks to Richard Highton who pointed out an error in the locality…Mr. Highton had also collected specimens of the new form, but since I had first reported and studied the form I feel free to describe it here.”

Highton did not agree.

As Highton wrote many years later, “Richard [Hoffman] was again subjected to receiving nasty letters between herpetologists, Thurow and me!” He did not go into detail about what the messages contained. We’ll probably never know what these letters said, but I would give a lot to get to read them.

And thus, the Peaks of Otter salamander entered the realm of official scientific description. From there, it has become the basis for a surprisingly rich body of research. Its life history has been reasonably well-studied, and the impacts of logging, roads and trails, cover objects, and competition with red-backed salamanders on the species have all been investigated.

The three researchers, meanwhile, went down rather different paths. Gordon Thurow became a professor of biology at Western Illinois University, and ultimately published a handful of interesting herpetology papers, including the first description of a caecilian producing sound. Richard Highton, meanwhile, became one of the most successful herpetologists in the country, focusing most of his research on Plethodon salamanders. He described 23 members of the genus over the course of his career and sampled 70,000 individual salamanders across 1,500 populations. As Ohio University herpetologist Shawn Kuchta wrote in 2019, “no one has ever known more about Plethodon, no one will ever know more about Plethodon, than Richard Highton.”

Richard Hoffman, meanwhile, had had enough of herpetology and its drama. Instead, he became perhaps the foremost authority on millipedes in North America. Over the course of his career, he published over 380 scientific papers on millipedes and described over 400 species and subspecies. In 2009, the Virginia Natural History Museum, where Hoffman served as a invertebrate curator for twenty years, published a festschrift — a collection of academic papers to celebrate an academic’s career — in honor of him for his 80th birthday. It was in that festschrift that Highton first published the full story of the Peaks of Otter salamander controversy. The piece is evidence of Highton and Hoffman’s deep friendship — and given his snippy tone, evidence that Highton and Thurow never fully made up after the incident.

As a final coda, remember that undescribed salamander that Hoffman sent to Netting and Mittleman that caused them to fall out? Amongst all the fighting, Netting and Mittleman never got around to describing it. No one did, in fact, until Highton in 1972. The scientific name he chose for it was Plethodon hoffmani, in honor of his good friend and co-discoverer of the Peaks of Otter salamander.

Say what you will about naming animals after people, but that’s pretty cute.

This was in 2024, and I was traveling with my girlfriend, Cassie, and my friend, Aidan. They had both been to Southeast Asia before. Cassie visited Laos in college to work on an elephant research project, and Aidan had been to Indonesia and Malaysia to travel and look for birds. Meanwhile, I had never been to the region at all, nor anywhere else in Asia. Everything was brand-new.

There were plenty of animals I wanted to see on this trip, but gibbons might have held the top spot. I’d dreamed of seeing these apes since I was a kid. Any time they appeared in a nature documentary, I was awed by the strange, effortless way they moved through the trees. They swung between branches with their long arms, body held steady, like a camera attached to a stabilizing rig. It looked more like surfing through the trees than swinging.

A few days into our trip, we finally reached Cat Tien National Park, where we hoped to see gibbons in the wild. This park is arguably the best place in the world to see the yellow-cheeked gibbon, an endangered species found only in Vietnam, Laos, and Cambodia. Throughout the park, gibbon troupes roam, and behind the park headquarters, there’s a primate research center that houses a handful of gibbons that were injured or seized from poachers, where they are rehabilitated and returned to the wild. Indeed, some of those wild troupes have formerly captive gibbons in them.

We were hoping we’d luck into seeing one of these wild troupes. On the first morning, within minutes of stepping out of our cabin at dawn, it became clear we wouldn’t need much luck.

The air was filled with the hollering of gibbons (see Aidan’s recording below). It was an otherworldly sound, a chorus of rising whistles crescendoing in dramatic wails and a series of descending chirps that sounded like a laser firing. The sounds were loud — we could hear them from half a mile away. As we approached the source of the sound near the park headquarters, the whole group became visible in the massive dipterocarp trees. Black males with white jowls hung from branches and yellow females with soft dark faces sat with babies clinging to their backs, all hollering. They weren’t just calling to each other, though. The troupe seemed to have come here to perch above the outdoor enclosures of the primate research center where the captive apes were held. They called down to their captive kin, who joined in the chorus in return. It seemed that the wild gibbons had come to check in on them. “We’re here,” they seemed to be saying. "It’s going to be okay.”

For the rest of our time in Cat Tien, this daily din of gibbon sounds was our alarm clock, and we came to watch them most mornings. Cassie began to refer it as “the Gibboning Hour.” I looked forward to hearing the sound every morning we spent in the park.

I was reminded of the Gibboning Hour recently because of a new study that looked at another species of gibbon — one that is far more endangered than the yellow-cheeked — and tried to understand how its population has tripled in the last two decades.

In 2003, there were only 13 Hainan black crested Gibbons on the planet. This made them the rarest primate on Earth, and one of the rarest mammals altogether. This rarity is relatively recent, though — into the middle of the 20th century, around 2,000 of these apes lived in tropical lowland rainforests across the island of Hainan off the southern coast of mainland China. Then, in the wake of Mao’s death, Chairman Deng Xiaoping began “opening up” China to outside business. Hainan proved to be a fertile ground for forestry and rubber plantations. Workers came in to work these industries, and the population of the island tripled, turning forests into houses, roads, factories, and farms. Within a few decades, 95% of Hainan’s forests were destroyed, and the remaining gibbons were pushed into a few hard-to-develop mountain slopes.

These remaining gibbons faced another threat, too — they’re worth a lot of money. To this day, Hainan has a lot of poverty, and in the early 2000s the average annual income sat around 60$ USD. A female Hainan black crested gibbon, meanwhile, sold for 300$. Even dead gibbons fetch a high price, as their bones are ground into a traditional arthritis cream called Houzi. Because of all these incentives, there have been a few particularly brutal episodes of gibbon slaughter on Hainan, including one instance where an entire mountain’s worth of gibbons were eradicated by employees of the Jianfengling Forestry Bureau’s 5th Logging Company.

In 1995, the government of Hainan finally ended the timber harvest on the island and declared it illegal for anyone to approach wild gibbons. The population stabilized, but it was as close to too late as you could get — those 13 gibbons were all that remained, and only two of them were males. A 2005 paper about the species (from which I drew many of these historical details), declared simply that “Hainan Black-crested Gibbon Is Headed For Extinction.”

But that’s not what happened. Thanks to intensive habitat protection, anti-poaching measures, and awareness campaigns by the Chinese government (plus a controversial campaign to resettle people living in Hainan’s mountains — for more on the human component see this great feature in bioGraphic), the Hainan black-crested gibbon population grew from 13 to 46 in the last 20 years. It’s still an extremely low number, but it’s evidence that, with the proper protections, these gibbons might be able to recover.

The problem with this extreme recovery, though, is that it leaves the population susceptible to inbreeding. Every single gibbon alive today is descended from just 13 individuals, including only two males. Typically, inbred animals have very similar genetics, which can lead to the accumulation of detrimental mutations.

Mutations can be dangerous even for animals with no inbreeding, but inbreeding makes the problem far worse. To understand why, imagine genes as instruction manuals for the body, and when they are mutated, they become a little bit harder to read. Every offspring gets one copy of each gene from its mother and one from its father. If, say, one copy of a father’s gene is mutated, but his female partner has the healthy gene, all of their offspring that inherit their father’s mutated gene will still be able to refer to their mother’s unmutated gene. But then, if these siblings breed with each other, they each might pass on their mutated copy of the gene, and their offspring will have no unmutated copy. All of a sudden, that offspring has a less legible instruction manual for that trait — if it happens a few more times, that trait could be lost entirely. Repeat this process over and over, and before long you’ll have a whole population with missing traits, making them less fit and more susceptible to disease.

This scenario is exactly what scientists figured would happen with Hainan black-crested gibbon. Then, this week, a study actually looked at their genetics (by following the gibbons around, waiting for them to poop, and collecting their droppings — field work is rarely glamorous). They found that, yes, the gibbons have low genetic diversity, but they weren’t particularly inbred, nor did they have very many negative mutations. In fact, their inbreeding levels were the lowest of 19 studied threatened primates, and on par with most unthreatened primates. For some traits, they were actually less inbred than their unthreatened counterparts.

In other words, Hainan black-crested gibbon appears to have solved inbreeding entirely. How?

First of all, it turns out that today’s gibbons weren’t actually descended from one group, but two. At the population nadir 20 years ago, those two males and their respective harems of females were each from a different population that had been separated for 450 years. In other words, before only a few decades ago, Hainan’s gibbons experienced little-to-on inbreeding.

But there’s more to the puzzle than that. These researchers also found that this population collapse was not the first time Hainan black-crested gibbons had weathered such a crisis.

In their DNA, the studies authors found evidence that Hainan black-crested gibbon populations plummeted down to as little as 100 individuals about a million years ago. This massive decline was probably due to the Ice Age turning rainforest into savannah, leaving gibbons with very little habitat. In order to survive, these gibbons had to take a more active role in their genetic variation.

During this crisis, evolution began selecting for gibbons that “recombined” their DNA a lot before passing it on to their offspring — essentially mixing up the two copies of each gene a bunch. This way, if one gene had a handful of mutations, those mutations didn’t all accumulate on one copy of the gene and were instead evenly spread across each copy of these apes’ genes. This process kept most of the “instruction manuals” readable, and ensured that each ape didn’t have too many mutations in its genes.

The researchers found that this “balancing selection” — the tendency to select for multiple versions of a gene within a population instead of one — operated particularly strongly on genes for sperm strength and the protein that digest diverse carbohydrates. These traits likely meant that Hainan black-crested gibbons were particularly good at breeding and adapting to rapidly-changing food sources, which may have been the key to their success during their population collapse a million years ago. As the Ice Age waned and the forest returned, the gibbons bounced back, and their population recovered to the 10s of 1000s across the island.

Today’s gibbons are the inheritors of these adaptations. In all probability, inbreeding should have wiped them out, too, just like it should have wiped out their Ice Age ancestors. But thanks to this past population collapse — and the resiliency of their ancestors — Hainan black-crested gibbon are recovering. Like the gibbons held at the primate research center at Cat Tien National Park, they need human help to survive. But they have on their side the guiding hand of their ancestors, calling out to them across a million years of time. “We’re here,” they seem to say. “It’s going to be okay.”

It’s worth dwelling on that for a second. There was a permanent ice cap that stretched from the Arctic into the modern Lower 48 that was four times as tall as the Empire State Building. No Canada, no New England, no Midwest. Just ice. It feels apocalyptic.

It goes without saying that the last glaciation (known as the Laurentian Ice Sheet) defined modern North American biogeography. The glacier wiped the land all but clean of life, then left behind brand new landforms — the Great Lakes, the Upper Mississippi River, Cape Cod — as it receded. Nearly every animal and plant that lives in this land today arrived after the glacier slunk back north.

But just as significant as the regions that were covered and gored by the glacier are the spots that were left untouched.

If you look at a map of the Laurentian Ice Sheet at its peak, you’ll see a pretty consistent line on its southern edge heading east along the modern Canadian-American border, then dipping south through the midwest and over to the Atlantic. But about halfway through, there is a little ice-free notch. This is known as the Driftless Area.

The Driftless Area encompasses parts of modern day Wisconsin, Iowa, Minnesota, and Illinois. This area was untouched by not just by the last glaciation, but over two millions years of previous glaciations too, meaning it lacks the sediment left behind by retreating glaciers (which is known as drift). Even as these older glaciers stretched their icy fingers down to modern Kentucky and St. Louis, the Driftless Area remained untouched.

In this way, the Driftless Area is unlike any other environment in the Midwest. Because the Driftless Area lacks a layer of glacial sediment, its top layer of rock is much, much older than in the rest of the Midwest — several hundreds of millions of years older. It’s this top layer of rock that is home to, in my opinion, one of the most absurdly specific habitat specialists I have ever encountered.

Meet Discus macclintocki — the Iowa Pleistocene snail.

On its face, the Iowa Pleistocene snail looks like your run-of-the-mill land snail. It’s tiny, about half the size of your pinky nail, with a flat, curled shell. Perhaps the first sign that something is unusual about this snail is the way that it was discovered — its shells were first found within sediment deposits that were at least 17,000 years old.

It wasn’t a particularly flashy discovery. This research, led by malacologist Frank Collins Baker, catalogued the animal life found within a sediment deposit in Illinois dating between 27,000 and 17,000 years ago. The Iowa Pleistocene snail was one of several species discovered there. A handful of its shells were found within the deposit, suggesting it was reasonably common in that prehistoric environment, then it was described, catalogued, and largely forgotten about.

This discovery is where it gets the “Pleistocene” part of its name, after the geological period its remains originated from. The Iowa part of its name came later, thanks to the work of an amateur snail biologist named Leslie Hubricht.

As Field Museum invertebrate expert Jochen Gerber wrote, Hubricht was an antisocial, obsessive man who turned up his nose at academia and competed endlessly with his colleagues. He was also one of the greatest experts on the molluscs of eastern North America to ever live. He described over 100 species of snails, slugs, and other molluscs, and expanded our knowledge on countless more, all while working full-time as a mechanic. As Gerber writes, “Hubricht’s scientific achievements would have been very considerable for any professional malacologist with the resources of a museum or university at his hands…It is amazing that Hubricht accomplished them with only a rudimentary formal education, without the infrastructure provided by a major institution, without financial support, mostly without collaborators, and in the spare time left to him by his full-time job.”

It was in that spare time that, in 1955, Hubricht ventured into the caves in Bixby State Preserve in northeastern Iowa in search of snails. There, in a cave “from which a continuous blast of cold air (temperature of about 50° F) issues,” he found a living population of the Iowa Pleistocene snail. Hubricht was surely excited to have found this prehistoric snail alive and well. What he didn’t realize was that he had stumbled upon something far bigger than one snail — an incredibly rare ecosystem found almost exclusively in the Driftless Area called the algific talus slope.

There are three things that define an algific talus slope: 1) it is primarily made of limestone, 2) its slope faces north or east, and 3) it is full of cracks. This last ingredient is the most crucial. As water rains down on these slopes, it seeps into these cracks and sinkholes and collects deep within caves. In the winter, that water freezes into ice that stays frozen year round. Throughout the warmer seasons, air rushes into these same cracks, cools as it passes over the ice, and pours out from cracks along the slope. Thanks to this system, the slope remains an incredibly stable environment. Even on scorching 100° summer days, the slope itself remains consistently below 50° F. It is at these cave entrances that Iowa Pleistocene snails thrive, feeding on dead plant matter from the ferns and mosses that carpet these slopes and the ashes and birches that grow overhead.

This system that the snails rely on is incredibly delicate. If it were much further south, the cave ice would not stay frozen all summer long. If it were much further north, it would get too cold for the snail to survive the winter — the species can only survive in temperatures between 50°F and 14°F. If the geology were slightly different, too, this whole system likely wouldn’t exist in the first place. The limestone beds that create this habitat exist throughout the Midwest, but the habitat itself only exists within the Driftless Area — everywhere else, that limestone is buried beneath a thick layer of glacial sediment and this snail cannot survive. It is only a quirk of glaciation that this snail still survives.

But while the glaciers nearly destroyed all of the snail’s modern habitat, they also may have allowed the snail to exist in the first place. The fact that there were so many shells in prehistoric deposits suggests that these snails were once more common. Perhaps the presence of a massive ice wall kept temperatures lower in the summer like a large scale algific talus slope ice cave, expanding the snail’s possible range. Then, once the glaciers retreated, the snails congregated around the only places that had ice year-round — which just so happened to be the places the glaciers left untouched. This delicate dance of glaciers is the only reason the Iowa Pleistocene snail exists today. In my mind, it is as much a hallmark of the Ice Age as the mammoths or giant ground sloths.

Today, the Iowa Pleistocene snail is only known from 37 algific talus slopes, all but one of which are in northeastern Iowa. Because of how delicate its habitat is, it is no surprise that it been on the federal endangered species list since 1978. It is threatened by development and human activity (the exact locations of its 37 sites where the snails are found is a closely guarded secret), but its most existential threat is, of course, climate change. If temperatures keep ratcheting up and Iowa becomes warmer, more and more talus slopes won’t freeze in the summer, and the snail won’t have anywhere to retreat to. Like mammoths and ground sloth, it risks becoming another relic of a bygone age — another piece of biodiversity, lost to human domination and a warming world.

The story of the Iowa Pleistocene snail reminds me of the work of another Driftless Area resident: Aldo Leopold, the great conservationist-philosopher whose shack in Baraboo, Wisconsin provides the setting for his posthumous essay collection, A Sand County Almanac. More specifically, it reminds me of my favorite essay in that collection, Draba. It’s a short piece, a mere 196 words. It describes the title flower, its place within the ecosystem, and then concludes with one of the best paragraphs ever written about nature:

Draba plucks no heartstrings. Its perfume, if there is any, is lost in the gusty winds. Its color is plain white. Its leaves wear a sensible woolly coat. Nothing eats it; it is too small. No poets sing of it. Some botanist once gave it a Latin name, and then forgot it.

Altogether it is of no importance—just a small creature that does a small job quickly and well.

One could write a similar paragraph about the Iowa Pleistocene Snail, a small creature whose place in the world exists by chance, who lives on the edge of existence, and who is of no importance to the world beyond the talus slopes. Perhaps, though, it’s worth going one step further — it is only by dispensing with the notion that a creature needs to be important that we can step back and recognize how miraculous its very existence is.

But sometimes, that split is anything but subtle.

Around 5.3 million years ago, the Mediterranean basin was cut off from the Atlantic Ocean. This period is known as the Messinian Salinity Crisis — over the course of between 400,000 and 600,000 years, nearly the entire basin dried up, and what water remained was as salty as the Dead Sea is today. Animals like mice, deer, goats, salamanders, and even elephants could wander the seabed with ease.

Then, one day, the Strait of Gibraltar opened.

Researchers disagree about exactly how fast it happened, but it was fast. And violent. As geologists Daniel García-Castellanos and Paul Carling describe in a piece in The Conversation, trillions of gallons of ocean water rushed through the newly formed gap at over 70 miles per hour and 1,000 times the volume of the Amazon River. It traveled down a kilometer-high hillside and hit with such force that it carved a skyscraper-deep trough into the ground. It was a natural disaster comparable to a supervolcano erupting.

Within a little as a few months, the basin was full.

For the animals that lived in the hypersaline water, this flood was a catastrophe —around 90% of native fish species died in the flood. Surely similar disasters happened for land animals as burrows flooded, herds were swept away, and entire ecosystems were wiped off the map. But as the water levels rose, the mountains within the basin turned into islands: Sicily, Ibiza, Crete, Cyprus. On these islands, a few land animals managed to avoid the floods. Separated so dramatically from the rest of their species, these animals were free to evolve in surprising ways.

Take Myotragus balearicus, a foot-and-a-half-tall “goat-antelope” native to the Balearic Islands in the western Mediterranean. It had forward-facing eyes like a predator, poorly-developed ankles that likely gave it a wobbly gait, a diet mostly consisting of toxic Balearic boxwood, and constantly-growing teeth like a rodent.

These adaptations are all a response to the lack of predators on these islands. Without anything hunting them, there was no need for a sturdy build, sideways-facing eyes, or quick locomotion, and with food in relatively short supply on the islands, Myotragus benefited by shrinking its body, brain, and muscles to save energy.

While Myotragus shrunk, other animals grew. The Balearics were also home to a group of giant dormice called Hypnomys (around double the size of mainland dormice), a giant shrew called Nesiotites (around triple the size of mainland shrews), and my personal favorite, a giant rabbit known as Nuralagus rex. Coming in at a whopping 18 pounds, N. rex was the largest rabbit to have ever lived, more than ten times larger than a wild European rabbit. Even Flemish giants, the largest rabbits that breeders have managed to create, are merely half the size of these island giants. N. rex was so big it couldn’t even hop.

These two phenomena — large animals shrinking and small animals growing — are the two hallmarks of a phenomenon known as the “Island Rule”. On islands, predation is limited, so large herbivores shrink to save energy rather than protect themselves and small herbivores grow to compete with each other rather than hide.

And if the Galapagos are the poster child for adaptive radiation, then the Mediterranean islands should be the poster child for the island rule.

We see this same phenomenon repeated again and again. There was a dormouse on Malta that was fourteen times the size of its mainland relative and a dwarf hippopotamus on Cyprus that was a mere 4% of the size of its ancestor. Crete had a mouse that septupled in size and a 16 inch tall deer with antlers as long as its body. Most striking of all, Sicily was home to both a two-foot-long giant tortoise and a 3-foot-tall dwarf elephant.

Later, subsequent waves of animal migration changed the diversity of these islands again. Tilos in modern-day Greece gained a dwarf elephant of its own, while Sicily gained an endemic wolf subspecies and a flightless swan that towered over its dwarf elephants. Sardinia and Corsica in particular developed a diverse collection of endemic animals, many of whom speed-ran the island rule — a dwarf mammoth and a dwarf deer, a large pika that was hunted by a tiny dog called the Sardinian dhole, both a giant otter and a dwarf otter, and a giant weasel-like animal related to modern-day polecats.

What happened to all of these animals?

Some of them went extinct due to climate change or the arrival of new competitors — the giant rabbit Nuralagus rex, for instance, likely went extinct when Myotragus reached its island and outcompeted it for resources. Many more went extinct when the first human settlers reached these islands. This, I would argue, isn’t really the early humans’ fault, but rather a natural consequence of a new apex predator reaching a previously untouched environment.

But a few animals held on a little longer until another wave of extinctions arrived. The tiny Mus minotaurus, or “Minotaur mouse,” of Crete and a dwarf elephant on Tilos may have gone extinct during the Bronze age, and Sardinia lost its native vole, mole, and pika when Roman forces took over the island. We don’t think of the Roman Empire as a biologically destructive force in the same way the British or American Empires have been, but something about centralized states seems to spell doom for the animals on their frontiers. More recently, the Sicilian wolf held on well into the modern age until it was finally killed by farmers in the 20th century.

I’ve been thinking about these animals a lot lately because they stand in stark contrast to an assumption that, I think, a lot of us hold: that Europe is biologically boring.

On some level, it’s true. Europe has less biodiversity than any continent besides Antarctica, and certainly has the fewest large intact natural areas — no Amazon, no Outback, no Congo Rainforest. Nearly every cool animal found in it is also found in Africa or Asia.

But this perceived “boringness” is partially due to how much humans have changed the continent’s animal life. There was an initial wave of extinctions when humans arrived, just like everywhere else, but this was followed by many more extinctions tied to imperial expansion and societal changes. There were leopards in Ancient Greece, pelicans in Roman Britain, a massive cow that went extinct in Poland in the 1600s. All of these animals were driven to extinction by humans, and with each extinction, the ecological baseline shifted further and further.

Thanks to this shifted baseline, though, one might assume the continent has little left to care about, ecologically speaking. But there is still plenty special in Europe. Nowhere is that clearer than with the Mediterranean islands’ reptiles and amphibians.

You could spend a lifetime hopping from island to island and still struggle to see all these reptiles and amphibians. Sardinia alone has six species of endemic salamanders, representing around 10% of Europe’s total salamander diversity. Crete, Cyprus, Rhodes, and Majorca are each home to a frog found nowhere else. There are a plethora of endemic lizards, including the Aeolian Wall Lizard, which is only found on three tiny volcanos off the Italian coast. Milos wall lizards, endemic to the Cyclades archipelago, are hunted by the Cyclades blunt-nosed viper, which is also endemic to that archipelago. This viper is a third the length of is mainland relatives —like the hippos of Cyprus and Myotragus of the Balaerics, it is an island dwarf.

These animals are no less extraordinary than the extinct animals they shared their islands with. They survived a biblical flood that created a land of giants and dwarves, then eked out a living as invasion after invasion of outsiders struck down their compatriots. They are a reminder of what once was and is, of the former and present diversity of this strange sea. They may not be dwarf elephants or giant rabbits, but they are no less worthy of awe.

Nearly all of these animals are under threat from some combination of climate change, development, introduced species, and hunting, not unlike the animals of the past. But we know what’s happening to them this time. More importantly, we know how to prevent them from meeting the same fate.

It’s a beautiful irony that the so-called “unnaturalness” of nearly any human identity can be easily corrected by looking at nature itself.

Animals just don’t seem to be confined to conventional notions of sexuality and gender. The discovery of lesbian gulls in the 1970s sent shockwaves through the homophobic right wing of American politics, but today, such discoveries have become commonplace. We have gay flying foxes, and bisexual tortoises. There are sparrows with basically four sexes and lizards with basically one. There are crayfish that seemingly evolved to favor intersexuality. Nearly every identity someone might choose has some parallel in the animal world — that parallel might be imperfect, but it will be there.

One such parallel that has stuck with me is the story of a little warbler named Y.

Y was a hooded warbler living in the Smithsonian Environmental Research Center, on the shores of the Chesapeake Bay, when ecologist Daniel Nevin first spotted it. Y caught Nevin’s attention because it had all the plumage characteristics of a male hooded warbler — particularly the namesake jet black hood — but it appeared to be making a nest.

Nevin figured that Y was simply a female bird with a particularly dark hood. Older female hooded warblers can develop male-like plumage, similar to how older human women can develop pronounced moustaches. Nonetheless, Nevin kept a close eye on Y and how other warblers behaved around it.

Y built its nest in the territory in the territory of a male warbler that Nevin called X. Nevin watched as X regularly sang near Y, with neither treating the other as a competitor as males typically would. Y, meanwhile, began sitting on its nest. Soon, X began feeding Y, apparently claiming the birds as one of its mates.

Somewhere along the line, another bird laid eggs in Y’s nest — possibly a brown-headed cowbird, which sometimes offloads parenting duties, or another female hooded warblers doing the same. Y began feeding these offspring as its own, with X coming to feed them too just as it did its young with other female warblers.

Sadly, Y’s young were eaten by a predator (a common fate for songbird nestlings) and Nevin didn’t see Y again that year. The following summer, however, Y returned, and paired up with a new male named Z. Again, Y built a nest, and this time, both a cowbird and another female warbler laid eggs in it. Again, Z fed Y while it incubated those eggs, and later those offspring when they hatched.

The following year, Y returned, and Nevin decided to collect it in order to perform a more detailed study on it. To Nevin’s shock, Y had well-developed testes and apparently functional sperm. Its body size and wing length fell squarely within the size range for male hooded warblers. And even up close, its hood seemed well-formed. “In all aspects of its anatomy, the bird was a male,” Nevin wrote, but its behavior — its self-expression, if you will — “was categorically female.”

Nevin can hopefully be forgiven for titling the paper simply “Male-Male Nesting Behavior in Hooded Warblers” when he published it in 1993. Today, I would argue, it seems clear that Y had something approaching a hooded warbler version of a trans identity. In other words, if I may anthropomorphize this bird: despite the body she was born with, she presented herself to the world differently.

There are plenty of takeaways from the story of Y. The study demonstrates that trans animals, or animals exhibiting something close to that idea, exist. It shows the value of deep research into individual wild animals. It suggests that this phenomenon may be far more common than we think, particularly in birds where females and males might look similar. But the one takeaway that sticks in my mind is the fact that all of the hooded warblers around Y treated her as female.

X and Z both treated Y as a viable mate. At least one female hooded warbler decided Y would make a good mother to her children. Hooded warbler society, such as it existed in that Maryland forest, accepted Y as a female.

This, to me, is the true lesson of this story. If hooded warblers can accept a trans member of their species as she is, then surely we can do the same.