Scientific name: Bison latifrons Scientific classification:
Phylum: Chordata Class: Mammalia Order: Artiodactyla Family: Bovidae
When did it become extinct? The giant bison became extinct sometime between 21,000 and 30,000 years ago.
Where did it live? This bison ranged widely across what are now the United States and southern Canada.
The modern American bison (Bison bison) is the quintessential American mammal. It is thought that 60 to 100 million bison roamed North America before the arrival of Europeans. As the settlers moved westward, they ravaged the bison herds until the species teetered on the brink of extinction. Fortunately, the bison received protection, and today, there are strong populations of this animal in several national parks in the United States and Canada as well as those living on private ranches.
The bison we know today is one of the last vestiges of the American megafauna, and these lands were actually home to several different kinds of bison, all of which originated from animals that migrated into North America from Asia via the Bering land bridge. It is still not clear if these fossils represent distinct species or geographical and temporal variants of a single, highly variable bison species. The ancestors of the bison evolved in Eurasia around 2 to 3 million years ago, and from there they spread, eventually reaching North America around 300,000 years ago. The North American continent was a land of opportunity, and these ancestral bison diversified into a range of forms, the most impressive of which was the giant bison. The modern plains bison is a big animal, with males reaching 2 m at the shoulder and 900 kg in weight; however, they would be dwarfed by a giant bison. This extinct species was around 2.5 m at the shoulder and could have weighed as much as 1,800 kg. Not only were they big, but the giant bison also had incredible horns. Like all bovids, the giant bison's horns were composed of a bone core surrounded by a keratin sheath. The sheath rots away to nothing after being buried for thousands of years, leaving us with just the bony cores curving out from the big skull. Some of these skulls have a horn span of just over 2 m, but in life, the keratin sheath made the span even wider, as is shown by a Californian specimen in which the outer sheaths were replaced by a sediment cast. Today's male American bison are far larger than the females, but this sexual dimorphism was even more pronounced in the giant bison. A fully grown male giant bison with its huge, shaggy forequarters and amazing horns must have stood out like a beacon amid the much smaller females.
The living bison is divided into two subspecies: the plains bison (B. bison bison) and the wood bison (B. bison athabascae). It is thought that the latter species has more in common with the giant bison in terms of behavior. The giant bison is not thought to have lived in the immense herds that the plains bison forms because despite its size, relatively few fossil specimens have been found in comparison to later bison. It may have formed, instead, small, close-knit family groups. The fossils of the giant bison have been found over a wide geographic area, and this could indicate that the animal was able to live in a variety of habitats, including forests and parklands as well as steppe grasslands, where it grazed on and browsed a wide range of plants.
Exactly how the giant bison used its enormous horns is not clear, but they were definitely important when it came to the breeding season. Males must have fought for the right to mate with as many females as possible, but it is likely that the males with the most impressive horns averted disputes through display, by simply intimidating their rivals with their size. Pleistocene North America supported a diverse population of predatory mammals, many of which were a match for a bison, even a giant one. The larger saber tooth cats, American lions, and wolves hunting in packs may have been able to overpower a fully grown giant bison, but tackling an adult male with its vicious horns and great strength must have been very dangerous. The predators of the giant bison most likely focused their attention on calves and on old and sick adults.
The giant bison seems to have vanished before humans arrived in North America, but it is unlikely it became extinct in the normal sense. As the giant bison adapted to the ever changing American landscape, it evolved into the smaller fossil species, the ancient bison (Bison anti-quus). Bison antiquus lived between about 20,000 and 10,000 years ago and, in turn, evolved into the modern bison. Mitochondrial DNA recovered from Bison antiquus is very similar to that of modern bison, demonstrating the association. No DNA has yet been recovered from the fossils of the giant bison, but there is a clear reduction in size moving from the giant bison, to the ancient bison, to the modern bison, providing a good example of evolutionary change.
The first humans to colonize North America, the Clovis culture, known from their widespread, distinctive flint arrowheads and spearheads, undoubtedly knew the ancient bison—the descendents of the giant bison—which, by Clovis times (about 13,000 years ago), was a grassland animal swelling in numbers. Along with the mammoths and the mastodons, this was still one of the larger land mammals of North America, and killing an adult probably provided a small group of humans with enough food for many weeks and an abundance of raw materials for making tools, shelter, and clothing. Is it possible that human hunting caused the demise of this bison? The likely answer is no. As with all the other great beasts that once roamed North America, we cannot attribute the disappearance of the ancient bison to a single event or factor. For almost the last 2 million years, the earth's flora and fauna have had to adapt to massive, cyclic climatic changes, some of which have been very abrupt: the glaciations and their associated interglacials (see the "Extinction Insight" in chapter 5). The inhabitants of the high and low latitudes have been most affected by these changes, but animals have the ability to migrate in the face of worsening conditions, even if it means that their populations may shrink. When humans arrived in North America, the giant bison had also felt the squeeze of climate change and had evolved into a smaller form, which in turn evolved into the smaller modern bison. Hunting probably had a considerable impact on populations, but bison were distinctive in being able to withstand these pressures and even to increase in number, until the arrival of the gun finally drove them to near-extinction in the nineteenth century.
♦ It is thought that the bison that migrated into North America from Asia were steppe bison (Bison priscus). They were, in turn, ancestral to the giant bison, which, through evolutionary change, spawned the two American bison subspecies we know today.
♦ In the United States and Canada, archeologists have unearthed what appear to be kill sites: locations where the first Americans processed the bodies of ancient bison for their meat, skin, bone, and sinew. Some of these sites have yielded the remains of hundreds of bison, which goes to show how important these animals were to the survival of prehistoric humans in North America.
♦ A species of bison also survives in Europe. The European bison, or wisent (Bison bonasus), is a forest-dwelling animal that once ranged over much of Eurasia. Hunting depleted its numbers, until the last wild specimen was killed in 1927. Fortunately, several wisent were kept in zoos and private collections, and these were used to start a reintroduction program. Today, thanks to reintroduction and protection, the largest European land animal can be found in several eastern European countries.
Further Reading: Guthrie, R. D. "Bison and Man in North America." Canadian Journal of Anthropology 1 (1980): 55-73; McDonald, J. N. North American Bison, Their Classification and Evolution. Berkeley: University of California Press, 1981.
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