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How Did Bears Evolve?

Evolution has fascinated me for as long as I can remember, and if you have read any of my bear articles, you will know that I love these animals. I wanted to find out how bears evolved, and the information I found was fascinating.

Bears evolved from small tree-climbing mammals in the family Miacidae about 60 million years ago. Their bodies, skulls, and teeth changed throughout time, along with their range and habitats worldwide. They traveled across the Bering land bridge around 1.3 million years ago to North America.

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

Bear chewing grass

What Were The Ancestors Of Bears?

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

The earliest bears were similar to raccoons and were small compared to today’s 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 Oligocene. These early amphicynodontines evolved into hemocyanins, with the Eurasian Cephalogale in the Oligocene relocating from Eurasia. Also migrating from Eurasia were the later Phoberocyon and Plithocyo,n which moved to North America.

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

Did Bears Evolve From Dogs?

Bears have been evolving for about forty million years, and fossils from the Miocene Epoch show bear and dog characteristics. 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 in Asia around 34 million years ago. The Cephalogale was arboreal and hunted prey through the treetops.

Ursavis elmesnsis was a small, domestic cat-sized mammal commonly known as the dawn bear. The dawn bear had several adaptations from the earlier Cephalogale, including changes to its teeth. It also did much of its hunting through the treetops.

The dawn bear could not only eat meat but also plant material as well. Reductions to the size of the carnassial teeth and molars allowed the dawn bear to grind and chew its food. This allowed them to eat a broader range of food, including plants. Ursavis elmensis, the dawn bear, can be found in Europe and is the oldest species of bear known.

These evolved into other members of the Ursavis family. Protursus, a wolf-sized animal, was one of these and is only known by a few fossils. Protursus belongs to the family Ailuridae, of which the red panda is the only living representative.

What Was The First Bear In The Modern Ursus Genre?

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

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

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

Want to find out if bears can climb trees? Click here

What Was The Cave Bear?

The Etruscan, or cave bears, were omnivores, with vegetation making up a large part of their diet. They were large mammals weighing up to 400 kg and were around during the Pliocene through Pleistocene. 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.

The cave bear evolved from Ursus minimus, the ancestor of Ursus arctos, and the extinct cave bear, Ursus spelaeus. It is thought to be one of the first bears to have the same amount of premolars as the modern Ursavus bears.

How Did the Bears Get To North America?

The giant short-faced bear Arctodus simus arrived 1.3 million years ago in North America. Many animals, including bears, traveled across the Bering land bridge, a strip of land between Asia and Alaska in the last ice age.

Known as the largest carnivorous land mammal ever, the giant short-faced bear stood up to 3 meters upright and was five feet tall on all fours. Also known as the bulldog bear due to its short snout, the giant short-faced bear weighed almost a ton.  

The bulldog bear was found in several North American and Canadian states, 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 short bodies but long legs. Their similarities to the bulldog come from their broad snout, low forehead, and eyes 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.

If you want to learn about bear hibernation, I have written this article

Ursinae

The subfamily of Ursinae began with Ursavus, spreading from Asia to North America about 20 million years ago. Ursinae ranged 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 spectacled bear traveled across the Panama land bridge to South America.

Black bears aren’t just black; polar bears don’t have white fur.  Please find out more in this article I wrote.

How Did The Brown Bear Evolve?

Ursus arctos, the modern brown bear, evolved in Asia. Brown bears can be found in North America and 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 became more widespread than the giant short-faced bear. Brown bears do not climb trees as black bears do, and one reason is their past non-forested habitats.

Do you want to find out if bears can climb trees? Find out here.

Black bear crossing field

How Did Black Bears Evolve?

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 crossed the Bering land bridge.

How Did Polar Bears Evolve?

The evolution of polar bears Ursus maritimus is challenging 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 very few fossils have been found, with some bones from 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.

Polar bears are apex predators.  Please find out how they hunt in this article I wrote.

What Is The Evidence For The Evolution Of Bears?

Fossils are the primary evidence, although present species and genetic evidence are also used. Fossils are rare for bears, with more significant parts being difficult to find. Jaws, bones, and other skeleton parts have been carbon-dated, and this process has been used to date them.

Carbon dating and mitochondrial and nuclear DNA have provided more clues to bears’ evolution.

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

Click here to find out which National Parks you can see bears here

References and Further Reading

Scientific Reports – The evolutionary history of bears is characterized by gene flow across species.

PNAS – Insights into bear evolution from a Pleistocene polar bear genome

Cambridge.org – Systematics, Evolution, and Genetics of Bears