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  Bears are mammals of the family Ursidae. They are caniforms, or doglike carnivorans, with the pinnipeds being their closest living relatives. Although only eight species of bears are extant, they are widespread, appearing in a wide variety of habitats throughout the Northern Hemisphere and partially in the Southern Hemisphere. Bears are found on the continents of North America, South America, Europe, and Asia.

Common characteristics of modern bears include large bodies with stocky legs, long snouts, shaggy hair, plantigrade paws with five nonretractile claws, and short tails. The polar bear is mostly carnivorous, the giant panda feeds almost entirely on bamboo, and the remaining six species are omnivorous with varied diets.

Except courting individuals and mothers with their young, bears are typically solitary animals. They are generally diurnal, but may be active during the night or twilight particularly around humans. Bears possess an excellent sense of smell and, despite their heavy build and awkward gait, are adept runners, climbers, and swimmers. In autumn, some bear species forage much fermented fruit, which affects their behaviour. Bears den in caves and burrows; most species occupy their dens during the winter for a long period of sleep that resembles hibernation.

Bears have been hunted since prehistoric times for their meat and fur. With their tremendous physical presence and charisma, they play a prominent role in the arts, mythology, and other cultural aspects of various human societies. In modern times, the bears' existence has been pressured through the encroachment on their habitats and the illegal trade of bears and bear parts, including the Asian bile bear market. The IUCN lists six bear species as vulnerable or endangered, and even least concern species, such as the brown bear, are at risk of extirpation in certain countries. The poaching and international trade of these most threatened populations are prohibited, but still ongoing.

Etymology

The English word "bear" comes from Old English '''' and belongs to a family of names for the bear in Germanic languages that originate from an adjective meaning "".

In Scandinavia, the word for bear is ', and is a relatively common given name for males. The use of this name is ancient and has been found mentioned in several runestone inscriptions.

The reconstructed Proto-Indo-European name of the bear is ', whence Sanskrit ', Avestan ', Greek, Latin ', Welsh ', Albanian ', Armenian . Also compared is Hittite '', the name of a monster or predator. Thus, some Indo-European language groups do not share the same PIE root.

Evolutionary history

The family Ursidae is one of 9 families in the suborder Caniformia, or "doglike" carnivores, within the order Carnivora. Bears' closest living relatives are the pinnipeds, canids, and musteloids.

The following synapomorphic traits set bears apart from related families:

presence of an alisphenoid canal

paroccipital processes that are large and not fused to the auditory bullae

auditory bullae are not enlarged

lacrimal bone is vestigial

cheek teeth are bunodont and hence indicative of a broad, hypocarnivorous diet taxa are known from the fossil record)

carnassials are flattened

Additionally, members of this family possess posteriorly oriented M2 postprotocrista molars, elongated m2 molars, and a reduction of the premolars.

Modern bears comprise eight species in three subfamilies: Ailuropodinae, Tremarctinae, and Ursinae .

Fossil bears

The earliest members of Ursidae belong to the extinct subfamily Amphicynodontinae, including Parictis and the slightly younger Allocyon, both from North America. These animals looked very different from today's bears, being small and raccoon-like in overall appearance, and diets perhaps more similar to that of a badger. Parictis does not appear in Eurasia and Africa until the Miocene. It is unclear whether late-Eocene ursids were also present in Eurasia, although faunal exchange across the Bering land bridge may have been possible during a major sea level low stand as early as the late Eocene and continuing into the early Oligocene. European genera morphologically are very similar to Allocyon, and also the much younger American Kolponomos, are known from the Oligocene, including Amphicticeps and Amphicynodon.

The raccoon-sized, dog-like Cephalogale is the oldest-known member of the subfamily Hemicyoninae, which first appeared during the middle Oligocene in Eurasia about 30 Mya ago. The subfamily also includes the younger genera Phoberocyon, and Plithocyon .

A Cephalogale-like species gave rise to the genus Ursavus during the early Oligocene ; this genus proliferated into many species in Asia and is ancestral to all living bears. Species of Ursavus subsequently entered North America, together with Amphicynodon and Cephalogale, during the early Miocene .

Members of the living lineages of bears diverged from Ursavus around 20 Mya ago, likely via the species Ursavus elmensis. Based on genetic and morphological data, the Ailuropodinae were the first to diverge from other living bears about 19 Mya ago, although no fossils of this group have been found before about 5 Mya. Their earliest fossil representative is Plionarctos in North America . This genus is probably the direct ancestor to the North American short-faced bears, the South American short-faced bears, and the spectacled bears, Tremarctos, represented by both an extinct North American species, and the lone surviving representative of the Tremarctinae, the South American spectacled bear .

The subfamily Ursinae experienced a dramatic proliferation of taxa about 5.3–4.5 Mya ago coincident with major environmental changes, with the first members of the genus Ursus also appearing around this time.

The fossil record of bears is exceptionally good. Direct ancestor-descendent relationships between individual species are often fairly well established, with sufficient intermediate forms known to make the precise cut-off between an ancestral and its daughter species subjective.

Other extinct bear genera include Agriarctos, Indarctos, and Agriotherium .

Taxonomic revisions of living bear species

The giant panda's taxonomy has long been debated. Its original

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