The Evolution of Bears

Evolutionary Roots and the Miacids

Most of what truly happened during the evolution of bears will remain forever shrouded in the mists of the distant past .....

From what we do know, however, we have been able to piece together that approximately 30 to 40 million years ago during the Oligocene period, a family of small, tree-climbing carnivorous mammals came into being.

These animals, now referred to as miacids, had developed special canine teeth which enabled them to pierce and tear the flesh of their prey. Additionally, the miacids had developed sharp-edged carnassial teeth (i.e., the last premolar in the upper jaw) and the first molar in the lower jaw. This development allowed the miacids to easily shear meat from a carcass into easily eaten smaller chunks of meat.

From an evolutionary perspective, these two developments led to the miacids becoming the precursor to all seven present carnivore families. Today, of the approximately 4500 mammals known to exist, 231 are classed as carnivores. All would become successful groups of predators. Included in the carnivore families are the following:

the Canidae (dog) family - 35 species including the fox, wolf, coyote and jackal;

the Procyonidae (raccoon) family - 16 species including the ringtail, kinkajou and raccoon;

the Mustelidae (weasel) family - 67 species including badger, otter and skunk;

the Viverridae (mongoose) family - 66 species including mongoose, genet and meercat;

the Hyaenidae (hyena) family - 4 species including spotted hyena, striped hyena, brown hyena and aardwolf;

the Felidae (cat) family - 35 species including leopard, cheetah and mountain lion;


the Ursidae (bear) family - eight species including the brown bear, the American black bear, the polar bear, the giant panda bear, the Asiatic black bear, the spectacled bear, the sloth bear and the sun bear.

Evolutionary Roots of the Modern Bear

The first bears are known to have evolved from a heavy bear-like dog that developed from the miacids. This animal is known to have existed sometime during the late Oligocene period, some 27 million years ago.

We also know that approximately 20 million years ago in subtropical Europe, a bear about the size of a small terrier existed. It is now referred to as Ursavis elemensis.

Approximately two and a half million years ago, the direct ancestors of our modern bears appeared on the planet. Members of this genus named Ursus (Latin for bear) later divided into three distinct evolutionary lines. Two of the lines were established in Asia and it is thought that they led to what is now the brown bear and the black bears. The third line developed in Europe.

From the European line of bears came the animal known as Ursus spelaus and often referred to in the literature as the "cave bear". Arriving in Europe approximately 30,000 to 40,000 years ago, they were a large mammal with large males weighing in excess of 400 kilograms (880 pounds). It is believed that they hibernated much as do our present bears and were opportunistic omnivores.

These bears appear to have both preyed upon and been the prey of our early human ancestors. Prior to recorded history, these animals had become extinct. Today, the European brown bear has taken over the habitat formerly occupied by the Ursus spelaus.

Another bear which has become extinct is Arctodus simus, commonly referred to as the short-faced "bulldog" bear. With remains of this bear discovered in the tar pits of southern California, it appears it arrived in North America via the Bering land bridge that at one time linked North America to Asia.

This bear, possibly the largest bear that ever existed, was significantly larger than the present day Kodiak brown bears of Alaska. It had exceptionally long legs adapted to swift pursuit of prey. It appears to have been very fierce and highly predatory in nature.

The "bulldog" bear disappeared approximately 12,000 years ago in the same time period which saw the extinction of mammoths, sabre-toothed cats and many other large mammals. Its habitat since has been taken over by the brown bear.


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