Bears are large mammals inhabiting diverse environments across North America, South America, Eurasia, and parts of the Southern Hemisphere. The eight living species exhibit characteristics such as stocky legs, long snouts, small rounded ears, and shaggy fur. Bears are generally solitary creatures, with most species being omnivorous. They thrive in habitats from icy Arctic regions to tropical forests.
Bears Place in the Animal Kingdom
Bears are classified within the hierarchical system of biological classification. They belong to the Kingdom Animalia, encompassing multicellular organisms that obtain nutrients by consuming others. Bears are part of the Phylum Chordata, characterized by a notochord and a dorsal hollow nerve cord at some point in their development. Within Chordata, bears fall under the Class Mammalia, sharing traits like being warm-blooded, having hair or fur, possessing mammary glands to nurse their young, and typically giving live birth.
Their classification continues into the Order Carnivora. Despite this, most bear species are omnivorous, consuming both plants and animals. The polar bear is primarily carnivorous, while the giant panda is almost exclusively herbivorous. All modern bears belong to the Family Ursidae.
Evolutionary Journey of Bears
The lineage of modern bears traces back to ancient carnivorous mammals called miacids, which emerged 30 to 40 million years ago during the Oligocene period. These small, tree-climbing animals possessed specialized canine and carnassial teeth. Miacids are considered the evolutionary precursors to all modern carnivore families, including Ursidae.
The Ursidae family diverged from other carnivores 20 to 25 million years ago, making bears a relatively young family within the Carnivora order. Early bears, such as Ursavis elemensis from subtropical Europe, were much smaller than current species. Modern bears developed changes in dentition, such as flattened molars for crushing vegetation, reflecting their varied diets. Their body size increased, and plantigrade paws, which allow them to walk flat-footed, became characteristic, aiding in their ability to dig and manipulate food.
Close Relatives within Carnivora
Bears are part of the suborder Caniformia, often called “dog-like” carnivorans, which includes dogs, raccoons, and mustelids. This suborder contrasts with Feliformia, or “cat-like” carnivorans. Within Caniformia, bears share a recent common ancestor with several other families.
The closest living relatives to bears are pinnipeds, including seals, sea lions, and walruses. Anatomical similarities in skull structure and genetic evidence support this close relationship, suggesting pinnipeds evolved from a bear-like terrestrial ancestor that adapted to an aquatic lifestyle. Other related families within Caniformia include Mustelids (weasels, otters, badgers) and Procyonids (raccoons, coatis). These groups, along with bears and pinnipeds, form part of the Arctoidea infraorder within Caniformia.