Unearthing the story of bears’ evolution

Photo: Martin Cathrae on Flickr
Fossil remains of a giant short-faced bear, an extinct species of bear that is one of the largest terrestrial carnivores known by scientists.

By Kayla Heinze, Communications Specialist

Living peacefully alongside bears can require innovation. Each year, as grizzlies emerge back onto the landscape, we begin our process of awarding grants to forward-thinking local communities working to prevent conflicts with wildlife. Many of their efforts blend modern technologies like drones and electric fencing with time-tested strategies like range riders and livestock guardian dogs. 

Coexistence is an increasingly urgent imperative. After decades of absence in many parts of their range, recovering bear populations are slowly expanding back into their historic habitat, meaning people unaccustomed to it must quickly adapt to the presence of these large and powerful mammals. Yet, for all the impressive inventiveness of these frontline endeavors, this is not entirely novel territory.

Wandering back through the caves of previous eras, we see that humans and bears have shared landscapes for far longer than we have been separate. As I unearthed some of these long-buried memories, about both our human ancestors and the remarkable predecessors of modern bears, I was struck by the substantial span of our shared history

As we sort through this year’s applications for our Conservation Partner Grants program, I am feeling hopeful that our species’ future together will be long too. 

Coexisting with Ancient Bears

Animal paintings by early humans from Chauvet Cave in France. (Photo: Claude Valette on Flickr)

Our first cave is called Chauvet-Pont-d’Arc. If you were alive some 32,000 years ago and wandering through the area now known as southeastern France, you may have stumbled across two fascinating creatures using this protected chamber. The aptly-named Cave Bear, Ursus spelaeus, used caves for hibernation, which is why as many as 3,700 of their bones have been uncovered at Chauvet. A close relative of modern brown bears, they went extinct during the last ice age around 24,000 years ago. 

Early humans also used the cave. Safe from harsh weather in its recesses, these people covered the walls with hundreds of animal paintings, including many of predatory species like lions, hyenas, and bears. 

While artistically beautiful, we cannot be certain about our ancestors’ motivation for making these paintings. Did they depict bears out of reverence? Or were the cave paintings made to record and share information, perhaps for purposes such as hunting or avoiding bear attacks? Regardless of their intention, we see clearly in the pigmented forms on Chauvet’s walls that bears have been occupying space in our cultural imagination for quite some time. 

Closer to home in California’s Potter Creek Cave, archeologists found the first fossil evidence of another prehistoric bear that once roamed widely across a North American continent shared with early Native American peoples. Arctodus simus, the giant short-faced bear, ruled the landscape until about 12,000 years ago when it died out with many other megafauna. Able to reach sizes upwards of 2,000 pounds and over 5 feet at the shoulder when walking on all fours, A. simus astonishes as one of the largest terrestrial mammalian carnivores ever known.

When early humans arrived here, likely at least 20,000 years ago, the still abundant and sizable A. simus would have been a force to be reckoned with. Presumed to have an omnivorous diet similar to modern grizzlies, it is possible A. simus competed with humans for food. We do not yet have evidence of hunting or predation occurring between early Native Americans and A. simus, though there are a few examples of cave bears being hunted in Europe. Regardless of how and to what extent they encountered one another, we know humans have been cohabitating with bears since they first arrived in North America.

Brown bears, American black bears, and polar bears (all members of the Ursus genus) were also present on the continent with these early humans and A. simus. It is theorized that the Ursus bears were more adaptable to the changing environment of the last ice age and eventually outcompeted A. simus to its extinction. But remnants of this marvelous, ancient creature still linger in a surprising place. 

The Diversity of Modern Bears

The spectacled bear, the only living descendant of the giant short-faced bears that once roamed the Americas. (Photo: Tambako the Jaguar on Flickr)

Climbing through the trees of the Andes Mountains is a small bear, weighing between 150 and 250 pounds on average. The primarily herbivorous Spectacled bear is the only living descendant of the short-faced bear subfamily to which A. simus belonged. While it has undergone dramatic changes from its giant ancestors, it still carries traces of their unique snout and molar morphology. 

The Spectacled bear is one of eight species of bear that we share the planet with today. Ancestors of the Giant Panda were the first to differentiate, splitting off from the rest of the bear family tree around 19 million years ago. Six of the modern species, the Sloth, Sun, Brown, Asiatic black, American black, and Polar bears, belong to the same subfamily, Ursinae, which experienced significant diversification around 5 million years ago — leading to the first members of the Ursus genus to which modern grizzlies belong. 

Each of these species is the current chapter in a continually unfolding evolutionary story. They are the product of eons and carry in their biology memories of previous chapters, pieces of now-extinct species like the cave bears and A. simus. Conserving habitat ensures that the story of modern bears can continue to be written and that we can witness (as our ancestors did) the stunning adaptations unfolding on their pages. 

Protecting the Products of Evolution

Since they came onto the evolutionary scene around 800,000 years ago, brown bears have endured an ever-changing world. As glaciers expanded and retreated, early humans spread across the globe, and prehistoric bears came in and out of existence, the most successful of the grizzlies passed on their genes to fill the landscape with offspring well-suited to the challenges of their day. But as European settlers spread across the American West, converting habitat to industrial use and hunting at unprecedented rates, the long history of these bears in the Lower 48 almost came to an end.

Luckily, our species continues to evolve too. Communities across the Northern Rockies and beyond are learning from the past and imagining new futures as they take seriously the call of coexistence. They know that if we give bear populations adequate space, the dynamic processes of nature will continue to shape this long-existing lineage in wondrous ways. 

Our grant program supports this essential work by keeping people, livestock, and wildlife safe on our shared landscapes, and our habitat protection projects aid rebounding grizzly populations as they reconnect and pass along the best of their genetic resources

Bears have been on this Earth for around 38 million years and we do not want their story to conclude on our watch. While we cannot guarantee the future in a world characterized by change, being part of this conservation community encourages me that the writing on the walls of our era’s caves will tell a story not just of destruction, but also of devotion.

Join us in caring for these remarkable creatures…

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