How Did Bears Evolve?


Evolution has fascinated me for some time and if you have read any of my bear articles then you will know that I love them too. I wanted to find out how bears evolved and the information I found was really interesting.

Bears evolved from small tree-climbing mammals. Throughout time, their bodies, skulls, and teeth changed along with their range and habitats in the world.

If you want to find out how bears evolved please read on.

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Early Bears

Species of bear alive today evolved from a family called Miacidae. Miacids were small, tree-climbing carnivores. Miacids lived in the Paleocene through Eocene epochs.  

These early animals were small and arboreal mammals. They were known to be carnivores due to their canine and carnassial teeth. The canine teeth were used to hold prey and pierce through their skin, while the carnassial teeth were used to tear off pieces of meat.

The earliest bears were similar to raccoons and were small compared to later bears. These early bears were called Parictis and lived in North America during the late Eocene.

Miacids branched off into two groups about 60 million years ago. These were the cat family and the dog family. The dog family (arctoids or vulpavines) were the ancestors of bears, with today’s wild dogs being their closest relatives.

Amphicynodon emigrated from North America to Eurasia in the early Oliogocene. These early amphicynodontines evolved into hemicyonines, with the Eurasian Cephalogale in the Oligocene emigrating from Eurasia. Also migrating from Eurasia were the later Phoberocyon and Plithocyon which moved to North America.

In the Miocene rocks of Washington and Oregon, an aquatic bear with mollusc-crushing teeth and a downturned snout had been found with the name of Kolponomos.

Did Bears Come From Dogs?

Bears have been evolving for about forty million years and fossils found from the Miocene Epoch show the characteristics of bears and dogs. The fossils of the Hemicyon (half dog) show the integrated evolutionary history of dogs, hyenas, wolves, and bears.

A small, dog-sized mammal (Cephalogale) appeared around 34 million years ago in Asia. The Cephalogale was arboreal and hunted prey through the treetops. The next ancestor also did much of its hunting in the treetops.  

Ursavis elemesnsis was a small, domestic cat-sized mammal commonly known as the dawn bear. The dawn bear had several adaptations form the earlier Cephalogale including changes to its teeth. 

The dawn bear could not only just eat meat but also plant material as well. Reductions to the size of the carnassial teeth along with molars allowed the dawn bear to grind and chew. This allowed them to eat a wider range of food including plants.

Ursavis elemensis, the dawn bear, could be found in Europe. They evolved into other members of the Ursavis family. Protursus was one of these. They were a wolf-sized animal known from only a few fossils.  

Etruscan bear

Ursus etruscus, the Etruscan bear appeared around five million years ago and was the first member of the Ursus genre. The Etruscan bear was found in southern Europe and fossils prove that they are the direct ancestor of the modern brown bears. They had large molars that could chew up a variety of plant materials.  

The Etruscan bear could be found in North America and Eurasia. It is believed from fossil records that brown, black, and polar bears evolved from this species.

Later, the Etruscan bear separated into two branches. One was the Asian brown bear and the other Ursus speleaus, known as the cave bear. The Etruscan bear died out around 1.3 million years ago.

Cave Bear

Cave bears were omnivores with vegetation making up a large part of their diet. They were large mammals weighing up to 400 kg. They had large bones making up their frame, along with a large skull.

These bears could be found in the mountains of France, Germany, and Russia until they died out around 11,000 years ago.

Arrival In North America

The giant short-faced bear (Arctodus simus) arrived in North America 1.3 million years ago. Known as the largest carnivorous land mammal ever, they stood up to 3 meters when upright and five feet tall on all fours. Also known as the bulldog bear due to their short snout, the giant short-faced bear weighed almost a ton.  

The bulldog bear could be found in several states in North America and Canada including California, Virginia, and Alaska. The largest specimens were found in the Yukon and Alaska.

Although they were the largest carnivorous land mammal they had a short body but with long legs. Their bulldog name comes from their broad snout, low forehead, and eyes that were set forward.  

The giant short-faced bear was thought to be the apex predator of its time.  

The giant short-faced bear was no longer seen after the mid-Pleistocene Period due to competition from the modern brown bear, Ursus arctos.

Ursinae

The subfamily of Ursinae began with Ursavus, spreading from Asia to North America about 20 million years ago.

Ursinae ranged in size from cat-size to wolf-size but all were carnivores with distinctive teeth.

Ursinae divided into two branches with the short-faced bears and the spectacled bears. The short-faced bears roamed around North and South America whereas the spectacles bear traveled to South America across the Panama land bridge.

Brown Bear

Ursus arctos, the modern brown bear evolved in Asia. Brown bears can be found in North America, along with many other species of Asian animals after they traveled across a strip of land called the Bering land bridge between Alaska and Asia in the last ice age. The fossils of brown bears have been found in Alaska dating 200,000 years ago.

Ursus arctos was not the first bear to travel over the Bering land bridge, with black bears arriving in North America 1.5 million years ago.  

The brown bear evolved to live in non-forested areas and as such became more widespread than the giant short-faced bear. Brown bears do not climb trees as black bears do and one of the reasons is due to their non-forested habitats in the past.

Polar Bear

The evolution of polar bears (Ursus maritimus) is difficult to pinpoint as they have fossils from the Ice Age. It is believed that 10,000 to 100,000 years ago, many brown bears far north along the Siberian coast developed white coats to help them blend in with their icy habitat.

Polar bears are hard to distinguish as there are very few fossils that have been found, with some bones that are 20,000 years ago.  

Bears did not just originate in Asia, with several species living in North America before the last ice age. Several animals with similar appearances evolved in different continents of the world, known as convergent evolution.

Black Bear

The American black bear (Ursus americanus) evolved along with Asiatic black bears. They evolved from the same line as the cave bear, descending from Ursus abstrusus, a small, primitive black bear.  

Ursus Euarctos, a black bear, came to North America during the Pliocene Epoch before the brown bear.

What Evidence Is There For The Evolution Of Bears?

Fossils are the primary evidence of the evolution of the bears, along with genetic evidence and present species. Fossils are quite rare for bears, with larger parts being very difficult to find. Jaws, bones, and other parts of the skeleton have been carbon-dated and this process has been used to date them. Carbon-dating along with mitochondrial DNA and nuclear DNA have provided more clues to the evolution of bears.

Both mitochondrial DNA and nuclear DNA have been very helpful in providing more evidence of the bear’s origins, with DNA showing that bears evolved earlier than fossil dating alone shows.

If you or someone you know loves bears then check out these great gifts on Amazon.

Bryan Harding

Bryan has spent his whole life around animals. While loving all animals, Bryan is especially fond of mammals and has studied and worked with them around the world. Not only does Bryan share his knowledge and experience with our readers, but he also serves as owner, editor, and publisher of North American Mammals.

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