Read Online The Great White Bear by Kieran Mulvaney - Free Book Online
Authors: Kieran Mulvaney
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Nor is the red panda, which shares with its larger namesake distinctive facial markings and a fondness for bamboo, a bear; rather, it appears to be more closely related to the raccoon.
For some time, there was considerable debate as to whether the great, or giant, panda was itself truly a bear. Its size suggests that it isâand indeed it was immediately identified as such by Père Armand David, the French priest and naturalist who was the first European to spy a panda pelt, and subsequently an actual panda, in 1869. But a panda's head and jaw are shaped more like a raccoon's, and whereas most bears are omnivorous with a tendency toward the carnivorous or insectivorous, pandas are almost exclusively vegetarian. Taxonomists debated for years whether the giant and red pandas were closely related, whether they should be grouped with raccoons or merited their own family. Ultimately, genetic studies demonstrated what anatomy alone could not: giant pandas are indeed bearsâare, in fact, the oldest of the bear species currently on Earth, having split off from the main ursid line about 10 million years ago.
Because of the giant panda's unique qualities and early divergence, taxonomists classify it in a subfamily, Ailuropodinae, of which it is the sole member. The spectacled bear also occupies its own subfamily, the Tremarctinae. The six remaining species have a more closely shared ancestry, having all diverged from the same branch of the family tree.
Before
Ursavus
departed this Earth for good, it begat
Protursus simpsoni,
which in turn led to
Ursus minimus.
The first true ursid,
Ursus minimus
was the approximate size of today's sun bear, although over the course of a few million years it apparently grew in size before giving rise to the yet larger
Ursus etruscus,
which was roughly equal in stature to the American black bear.
Etruscus
would in turn lead directly to the now-extinct cave bear of Europe, but it would also prove to be the granddaddy of six of the extant eight bear species: one branch led to the sun bear, one to the sloth bear, another to the Asiatic and then American black bears. * Then, between a million and a million and a half years ago, the brown bear made its maiden appearance, first in Europe, then Asia, and ultimately North America.
Finally, probably around 200,000 years ago, at much the same time as
Homo sapiens
was emerging in Africa, a new bear species took the stage. Clues to when, where, and how that came about are found in the brown bears of the Alexander Archipelago.
Studies have shown that the mitochondrial DNA of bears tends to change by about 6 percent every million years or so. The contention, repeated above, that brown bears split off from black bears around a million and a half years ago is supported by the observation that their mitochondrial DNA differs from that of black bears by between 7 and 9 percent. Polar bear DNA diverges from that of most brown bears by around 2.6 percent, which on its own might lead to the conclusion that polar bears evolved from brown bears a little under a half-million years ago. But the divergence between polar bear DNA and that of the Alexander Archipelago grizzlies (which themselves, according to the genetic clues, separated from the brown bear lineage between 550,000 and 750,000 years in the past) is a mere 1 percent, suggesting that their appearance is much more recent.
Any scenario to explain the sequence of events leading to the divergence of the Alexander Archipelago bears and the emergence of polar bears is inevitably and necessarily speculative. But thanks to the genetic evidence, such speculation is at least informed and allows us to paint a picture that looks something like this:
Half a million or so years ago, a stock of coastal brown bears in or near the Arctic became isolated, perhaps by surging glaciers or advancing sea ice. Sometime during the ensuing millennia, they began venturing out onto that ice, probably initially preying on young
For some time, there was considerable debate as to whether the great, or giant, panda was itself truly a bear. Its size suggests that it isâand indeed it was immediately identified as such by Père Armand David, the French priest and naturalist who was the first European to spy a panda pelt, and subsequently an actual panda, in 1869. But a panda's head and jaw are shaped more like a raccoon's, and whereas most bears are omnivorous with a tendency toward the carnivorous or insectivorous, pandas are almost exclusively vegetarian. Taxonomists debated for years whether the giant and red pandas were closely related, whether they should be grouped with raccoons or merited their own family. Ultimately, genetic studies demonstrated what anatomy alone could not: giant pandas are indeed bearsâare, in fact, the oldest of the bear species currently on Earth, having split off from the main ursid line about 10 million years ago.
Because of the giant panda's unique qualities and early divergence, taxonomists classify it in a subfamily, Ailuropodinae, of which it is the sole member. The spectacled bear also occupies its own subfamily, the Tremarctinae. The six remaining species have a more closely shared ancestry, having all diverged from the same branch of the family tree.
Before
Ursavus
departed this Earth for good, it begat
Protursus simpsoni,
which in turn led to
Ursus minimus.
The first true ursid,
Ursus minimus
was the approximate size of today's sun bear, although over the course of a few million years it apparently grew in size before giving rise to the yet larger
Ursus etruscus,
which was roughly equal in stature to the American black bear.
Etruscus
would in turn lead directly to the now-extinct cave bear of Europe, but it would also prove to be the granddaddy of six of the extant eight bear species: one branch led to the sun bear, one to the sloth bear, another to the Asiatic and then American black bears. * Then, between a million and a million and a half years ago, the brown bear made its maiden appearance, first in Europe, then Asia, and ultimately North America.
Finally, probably around 200,000 years ago, at much the same time as
Homo sapiens
was emerging in Africa, a new bear species took the stage. Clues to when, where, and how that came about are found in the brown bears of the Alexander Archipelago.
Studies have shown that the mitochondrial DNA of bears tends to change by about 6 percent every million years or so. The contention, repeated above, that brown bears split off from black bears around a million and a half years ago is supported by the observation that their mitochondrial DNA differs from that of black bears by between 7 and 9 percent. Polar bear DNA diverges from that of most brown bears by around 2.6 percent, which on its own might lead to the conclusion that polar bears evolved from brown bears a little under a half-million years ago. But the divergence between polar bear DNA and that of the Alexander Archipelago grizzlies (which themselves, according to the genetic clues, separated from the brown bear lineage between 550,000 and 750,000 years in the past) is a mere 1 percent, suggesting that their appearance is much more recent.
Any scenario to explain the sequence of events leading to the divergence of the Alexander Archipelago bears and the emergence of polar bears is inevitably and necessarily speculative. But thanks to the genetic evidence, such speculation is at least informed and allows us to paint a picture that looks something like this:
Half a million or so years ago, a stock of coastal brown bears in or near the Arctic became isolated, perhaps by surging glaciers or advancing sea ice. Sometime during the ensuing millennia, they began venturing out onto that ice, probably initially preying on young
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