The Great White Bear (6 page)

The ancient Greeks, analytical observers of worlds both celestial and terrestrial, determined that Earth was spherical, not flat. They noticed that Earth tilted in relation to the sun, offering first one hemisphere and then the other over the course of the year, and deduced that, because of that tilt, there had to be a line beyond which the sun neither set at the height of summer nor rose in midwinter. They calculated correctly that this line was 66 degrees north of the equator (and that there was an equivalent line 66 degrees south), and when they projected this line onto the celestial sphere that they imagined surrounded the earthly one, they noticed that it grazed the constellation of the Great Bear. To the Greeks, that constellation, like the species after which it was modeled, was called
Arktos,
and so the region that lay beneath it was the land of the bear,
Arktikos.

Furthermore, the reasoning continued, if there was a land to the north that lay beneath the Great Bear, then there must also be a counterbalancing landmass to the south. And if the northern lands were
Arktikos,
then those to the south must be the opposite—
Antarktikos.

The ability to predict the existence of the Arctic and Antarctic did not necessarily translate into an ability to portray them with any precision. Writing roughly two and a half thousand years ago, for example, the poet Pindar imagined a people called the Hyperboreans who lived "beyond the north wind." "Illnesses cannot touch them," he wrote, "nor is death preordained for this exalted race." Several hundred years afterward, the Roman geographer Pomponius Mela more accurately proposed that both the northern and southern realms were frigid, that each was flanked by a belt of more temperate climes, and that north and south were divided by an impassable torrid zone.

(Centuries later, this latter view and its subsequent variations ran headlong into Christian orthodoxy. If the southern land were unreachable because of the torrid zone, then its inhabitants could not be the descendants of Adam and Eve. Besides, Christ had commanded the Apostles to "go into all the world, and preach the gospel unto every creature"; the Bible did not record that they had visited this land;
therefore they had not been there; therefore it couldn't exist; therefore the world must not be spherical; therefore it must be flat.)

The Arctic and Antarctic have many things in common, not least the fact that, as Pomponius Mela correctly surmised, they are both, relative to the rest of the surface of the Earth, very cold—although the Antarctic is more so than the Arctic. Both, as also predicted, have periods of uninterrupted daylight in summer and seemingly endless night in winter. Each region surrounds its respective geographic pole: the North Pole in the Arctic, the South in the Antarctic.

But there are also differences.

Antarctica is a frozen continent in the Southern Hemisphere, surrounded by ocean. The Arctic is the northernmost ocean, encircled by land. Both regions boast whales and seals in their waters, but Antarctica and its environs have penguins, and the Arctic does not.

And the Arctic, unlike the Antarctic, has polar bears.

Polar bears are found only in the north, penguins only in the south; cartoons and Christmas cards notwithstanding, the paths of the two do not cross. Should a population of polar bears be picked up by a panhemispheric tornado and deposited on Antarctica, their stay would assuredly be brief; they would likely rampage through the resident seal and penguin populations during the summer but find themselves bereft of sustenance during the long, hostile Antarctic winter—when seals retreat to the sea and the coasts of sub-Antarctic islands and temperatures plunge to levels that would challenge even this hardiest of predators.

Defining the Antarctic is somewhat easier than delineating the Arctic. The conventionally acknowledged northern limit of the former is the Antarctic Convergence, where the cold waters of the Southern Ocean clash with warmer seas farther north and establish a genuine boundary between temperate and polar realms. In contrast, the outermost reaches of the Arctic are more land than sea, and accordingly there is no uninterrupted circumpolar current to provide similarly convenient demarcation.

Distance from the equator alone is an insufficient criterion for inclusion. For example, the Arctic Circle (the line at 66 degrees north of which the ancient Greeks were aware) excludes Iceland and large parts of Siberia; Berlin, which is plainly not an Arctic environment, is on the same latitude as the Siberian town of Irkutsk, which suffers winter temperatures as low as—40°F and therefore arguably is. Many authorities use as a boundary the 10°C isotherm, a term that neither trips off the tongue nor is intuitively simple to grasp. It refers to the line along which, during the warmest month of the year (usually July), the average temperature is no higher than 10°C (approximately 50°F ). That may seem somewhat arbitrary, but it does roughly correspond to the tree line, the point beyond which forest yields first to taiga (a region of scattered trees and scrub) and thence to tundra.

But there is another measure of greater relevance to our purposes: the southern limit of the winter pack ice. This encompasses all the waters that regularly freeze during winter, all the way south to James Bay in Canada, which is on the same latitude as England but is nonetheless, in terms of climate and ecology, Arctic in nature. It includes also Hudson Bay, Baffin Bay, Davis Strait, and Baffin, Banks, and Victoria islands in Canada; the coasts of Greenland; Svalbard and parts of the Barents Sea; Novaya Zemlya and the islands and coast of Siberia; the Kara, Laptev, and Chukchi seas off Russia; and the Bering Strait and Beaufort Sea off Alaska.

Not by coincidence, this is the range of the polar bear,
Ursus maritimus,
sea bear by scientific name and ice bear by nature. It is here, on the ice that covers bays and inlets, on the ice that is anchored to the coast, on the ice that drifts en masse offshore, on the ice at the Arctic's fringes, and even on the ice that encircles the North Pole, that the polar bear makes its home. It seems, to human eyes at least, desolate, a barren, hostile wasteland. Out of sight, however, below the feet of the prowling predator, the waters of the Arctic are rich in nutrients and life, some of which must occasionally come to the surface of water and ice to breathe and rest. It is in search of that life that the polar bear endlessly patrols its domain, a realm that it has made its own, to which it has, in a relatively short space of evolutionary time, become supremely well adapted.

To find a clue as to how that came to be, how, of all the bear species that live now or have existed in the past, just one should have ventured out onto the ice to hunt seals, we look to Alaska—not the icy coastal waters where polar bears roam today, but a very different environment indeed.

Of the many ways to explicate the scale of Alaska—the fact that it is twice the size of Texas, two and a half times as big as France, and almost six times as large as the United Kingdom; that it contains nineteen of the twenty tallest mountains in the United States, and the tallest in North America; the fact that its 35,000 miles of coastline, if somehow stretched into one long line, would encircle the equator with room to spare—the sheer diversity of its environments is one of the most impressive. The same state that in its northernmost reaches boasts tundra and sea ice is, in its southeastern region, lush and forested and regularly jammed with giant cruise ships.

There are no polar bears in southeastern Alaska, but there are brown, or grizzly, bears. There are many of them, in fact, particularly on three large islands—Admiralty, Baranof, and Chichagof, known colloquially as the ABC Islands—that form the northernmost extent of a 300-mile-long chain of mountainous island peaks called the Alexander Archipelago. There are three times as many brown bears as humans on Admiralty Island, 1,600 or so over an area of approximately one million acres, the highest density of brown bears in the world.

The grizzly bears of the ABC Islands are predominantly brown, with outer hairs that are often tipped with white or silver, giving them the "grizzled" appearance from which their nickname derives. They possess the large hump of muscle over their shoulders that distinguishes brown bears from other bear species. They eat roots and berries, fish, and small mammals. The males stake out territories and defend them fiercely from rivals. They look and act, in other words, like any other grizzlies.

But inside, they hold a secret.

The DNA of brown bears on Alexander Archipelago is different from that of brown bears anywhere else in the world. So distinct, in fact, is the DNA of the Alexander Archipelago bears from that of the rest of the world's grizzlies that other brown bears aren't even their closest relatives.

The Alexander Archipelago brown bears are most closely related to polar bears.

But we are getting ahead of ourselves.

We should begin at the beginning.

Polar bears are carnivores, and not only in that they eat meat. Indeed, they are the only truly carnivorous bear, as the other seven extant species are omnivorous or, in the case of the giant panda, effectively vegetarian. But they, and their bear brethren, are carnivores also in terms of their place in the great mammalian order of things.

All bear species alive today are members of the family Ursidae, in the order Carnivora, an order that includes the bulk of predatory mammals. (By way of comparison, human beings, along with bonobos, chimpanzees, gorillas, and orangutans, are generally—although not universally—grouped together in the family Hominidae within the order Primata, the latter of which also contains gibbons, monkeys, marmosets, and lemurs.)

The cat in your lap is a carnivore (in both the dietary and taxonomic senses), as are its larger relatives in the plains of Africa, the canyons of North America, and the jungles of South America and Asia. The family dog that sleeps at the foot of your bed, the raccoon that tips over the trash can at night, the skunk in the woods: all are members of the order Carnivora and thus relatives—second cousins, if you will—of the polar bear. Some, however, are more closely related than others. Generally speaking, cats and hyenas constitute one branch of the Carnivora family tree, and the remaining species—martens, minks, mongooses, weasels, wolverines, badgers, dogs, otters, seals, sea lions, and walruses—sit alongside bears on the other branch.

The progenitors of the Carnivora took their bow about 55 million years ago, around 65 million years after the appearance of the earliest true mammals and roughly 10 million years after a well-placed asteroid or two ushered the dinosaurs off the stage and allowed our mammalian ancestors—which, to that point, had mostly peered nervously at the proceedings around them from beneath bushes—to emerge blinking into the open.

Those progenitors, the miacids, were civetlike creatures, with long bodies and tails, that were likely mostly arboreal and probably fed primarily on insects and insect-eating animals like shrews. The Carnivora evolved from the miacids somewhat over 40 million years ago, and once they became established, they rapidly diversified. Within 5 to 7 million years, the dog, cat, weasel, and mongoose families had developed; and a little more than 10 million years after that—about 22 million years before the present—came the first bear.

Dubbed
Ursavus elemensis
and sometimes called the "dawn bear," it is known to us only from fragments of teeth and jaws. That is enough for paleontologists to determine it was about the size of a small terrier, but as to its appearance and habits we can only speculate. We can also only infer from an incomplete fossil record how it spawned other species and which species, in turn, evolved from those. We do know that by about 10 million years ago,
Ursavus
had disappeared, presumably as a consequence of climatic changes, the subtropical Europe in which it had evolved having become drier and the forests for which it was adapted having given way to steppes, plains, and desert. But where
Ursavus
fell by the wayside, others—evolving from either the dawn bear or contemporaries—emerged, spreading from Europe into Asia and thence the Americas. Some of the species that branched off from these lines have survived to the present day, while others, such as the cave bears of Europe and North America, and the giant, long-legged, short-faced bear—which at 2,200 pounds would have been approximately twice the size of most male polar bears—have long departed.

Today, eight species of bear—giant panda, sun, spectacled, sloth, Asiatic black, North American black, brown, and polar—are spread among four continents (Africa, Australia, and Antarctica being bearless). Each of them, in its own way, meets the more obvious visible criteria for a bear: a furry, essentially tailless, and somewhat sturdy body; wide paws with prominent claws; and a relatively large head with rounded ears and a muzzle less pointed than that of wolves. But within that broad generalization there are many differences, in size, shape, appearance, habitat, diet, and behavior.

Bears are generally caricatured as very large animals, and some of them truly are. But while the polar bear, the largest surviving bear species in the world, weighs in at up to 1,500 pounds or sometimes even more, the smallest, the sun bear—a denizen of the rainforests of Southeast Asia—is no bigger than a medium-sized dog and is in fact known in Thailand as a "dog bear" for that very reason. (Its more common name derives from a crescent-shaped patch on its chest.)

Bears' coloring ranges from the white appearance of the polar bear, through the black and white of the panda, to the darker pelage of the spectacled, sun, sloth, and appropriately named black bears. Their habitats extend from the Arctic Ocean surrounding the North Pole to the rainforests of Asia and South America and the river valleys, mountain forests, and meadows of North America and Europe.

Their feeding habits are similarly varied. The sun bear spends evenings scurrying along the rainforest floor in search of food and its days nesting in the branches of trees; across the Pacific, much the same is true of the Andean spectacled bear, the only extant bear species in South America and, in the view of many scientists, the closest living relative of the extinct giant short-faced bear. Feasting on anything from fruits to insects to small animals, both species are opportunistic feeders, as are brown and black bears, which will eat fish and carrion but also consume plants and berries. Polar bears, in contrast, are truly carnivorous, their diet dominated by seals; the giant panda is famously all but reliant on thirty species of bamboo; and the shaggy-haired sloth bear of the Indian subcontinent, Nepal, and Sri Lanka is almost exclusively insectivorous, consuming in particular vast amounts of ants and termites, using an extraordinarily powerful force of suction to remove them from their hills and mounds.