Woolly mammoth

The woolly mammoth (Mammuthus primigenius) is an extinct species of mammoth that lived from the Middle Pleistocene until it died out in the Holocene epoch. It was one of the last in a line of mammoth species, which began with the African Mammuthus subplanifrons in the early Pliocene. The woolly mammoth began to split off from the steppe mammoth about 800,000 years ago in Siberia. Its closest living relative is the Asian elephant. The Columbian mammoth (Mammuthus columbi) lived alongside the woolly mammoth in North America, and DNA studies show that the two hybridised with each other. Mammoth remains were known in Asia for a long time before Europeans learned about them. People long debated where these remains came from, and they were often explained as the bones of legendary creatures. In 1796, Georges Cuvier identified the mammoth as an extinct elephant species.

The woolly mammoth is one of the best studied of all prehistoric animals. Scientists learned about it from frozen bodies found in Siberia and North America, as well as from skeletons, teeth, stomach contents, dung, and pictures of the animal in prehistoric cave paintings. It was roughly the same size as modern African elephants. Males stood between 2.67 and 3.5 m (8 ft 9 in and 11 ft 6 in) tall at the shoulder and weighed between 3.9 and 8.2 t. Females stood 2.3 to 2.6 m (7 ft 7 in to 8 ft 6 in) tall at the shoulder and weighed between 2.8 and 4 t. A newborn calf weighed about 90 kg (200 lb).

The woolly mammoth was well suited to the cold environments of glacial periods, including the last ice age. It was covered in fur, with long guard hairs on the outside and a shorter undercoat beneath. The colour of its coat ranged from dark to light. Its ears and tail were small, which helped reduce frostbite and heat loss. It had long, curved tusks and four molars, which were replaced six times during an individual's life. It behaved much like modern elephants and used its tusks and trunk to handle objects, fight, and search for food. Its diet was mainly forbs and grasses, and individuals could probably live to the age of 60. It lived in the mammoth steppe, which stretched across northern Eurasia and North America.

The woolly mammoth lived at the same time as early humans, who hunted it for food and used its bones and tusks to make art, tools, and homes. Woolly mammoth populations declined at the end of the Late Pleistocene. The last populations on mainland Siberia lasted until around 10,000 years ago, while small, isolated groups survived on St. Paul Island until 5,600 years ago and on Wrangel Island until 4,000 years ago. After the species died out, people continued to use its ivory as a material, and this tradition continues today. The completion of the mammoth genome project in 2015 led to discussion about possibly reviving the woolly mammoth using several different methods. However, none of these approaches are currently feasible.

Taxonomy

Woolly mammoth remains were long known to native Siberians and Native Americans, who interpreted them in various ways. Remains later reached other parts of Asia and Europe, where they were also explained in various ways before modern science. The first woolly mammoth remains studied by scientists were examined by the British physician Hans Sloane in 1728. Sloane was the first to recognise that they belonged to elephants, but he linked them to the Great Flood, saying Siberia had once been tropical before a drastic climate change and that the flood had carried the elephants to the Arctic. In 1738, the German zoologist Johann Philipp Breyne argued that mammoth fossils were some kind of elephant. In 1796, French biologist Georges Cuvier was the first to identify the woolly mammoth as an entirely new species that had gone extinct. In 1799, the German naturalist Johann Friedrich Blumenbach gave it the scientific name Elephas primigenius, placing it in the same genus as the Asian elephant (Elephas maximus). In 1828, the British naturalist Joshua Brookes used the name Mammuthus borealis and thereby coined a new genus name. The origin of the word mammoth is unclear. It may come from an old Vogul word, or from the Arabic word mehemot, or from Estonian, where mutt means 'mole'. Thomas Jefferson, who was keenly interested in palaeontology, helped change the word from a name for the prehistoric elephant into an adjective for anything surprisingly large, as in the "Cheshire Mammoth Cheese" given to him in 1802. By the early 20th century, the taxonomy of extinct elephants was complex. In 1942, American palaeontologist Henry Fairfield Osborn's posthumous monograph on the Proboscidea was published. Later researchers from the 1970s onwards simplified mammoth taxonomy, keeping all species in the genus Mammuthus and treating many proposed differences as intraspecific variation.

Osborn chose two molars from Blumenbach's collection, found in Siberia and Osterode, as the lectotype specimens, since holotype designation was not practised in Blumenbach's time. One of the specimens Blumenbach had described was actually from the unrelated straight-tusked elephant (Palaeoloxodon antiquus). Soviet palaeontologist Vera Gromova later proposed that the Siberian molar be the lectotype. Both molars were thought lost by the 1980s, so the more complete "Taimyr mammoth" from Siberia was proposed as the neotype in 1990. The paralectotype molar has since been found in the Göttingen University collection. The earliest known members of the Proboscidea, the clade that includes modern elephants, lived about 55 million years ago around the Tethys Sea. Their closest relatives are the sirenians and the hyraxes. The family Elephantidae, which includes modern elephants and mammoths, existed 6 million years ago in Africa, while the mastodon is only a distant relative in the separate family Mammutidae. The Asian elephant is the closest living relative of mammoths. DNA studies from 2005 to 2006 confirmed the close relationship between mammoths and Asian elephants (Elephas maximus), and a 2015 review agreed. African elephants (Loxodonta africana) branched away around 6 million years ago, close to the time when chimpanzees and humans split. In 2008, much of the woolly mammoth's chromosomal DNA was mapped, showing it was 98.55% to 99.40% identical to the African elephant's. Mammoth species can be identified by the number of enamel ridges on their molars, which increased over time as species fed on tougher food. Woolly mammoths are thought to have split from the steppe mammoth about 800,000 years ago, and they had 26 ridges on their molars by about 400,000 years ago in Siberia. Woolly mammoths entered North America about 100,000 years ago by crossing the Bering Strait. Mammoth species and their intermediate forms blended into one another, so distinguishing them has been one of the most complicated problems in Quaternary palaeontology. Studies have shown that woolly and Columbian mammoths sometimes interbred. A 2021 study of DNA from much older mammoth teeth found that the first mammoths to reach the Americas were ancestors of the Columbian mammoth, and that the two lineages hybridised more than 420,000 years ago.

Description

Adult male woolly mammoths stood about 2.8 to 3.15 metres (9 ft 2 in to 10 ft 4 in) tall at the shoulder and weighed 4.5 to 6 tonnes. Females were smaller, like living elephants. This size was similar to the largest living elephant, the African bush elephant. Mammoths from Western Europe were larger than those from Siberia. Woolly mammoths had many features that helped them survive the cold, including a layer of fur over their whole body, small ears, a short tail, and a thick layer of fat under the skin. Their ears and tails were small to reduce heat loss and frostbite. Their large, high heads and sloping backs match how they appear in cave paintings, and their trunks had a long, pointed lobe at the tip.

Fur in Naturhistorisches Museum, Vienna (left), and SEM magnified image of an overhair

The coat had an outer layer of long, coarse hair and a denser, shorter inner layer of under-wool. The mammoth likely moulted in spring, when it lost its heaviest fur. Mammoths had sebaceous glands that produced oils, which helped keep the fur warm and water-repellent. Their tusks were very long and more curved than those of modern elephants, and they grew from modified incisor teeth. The longest known male tusk was 4.05 m (13.3 ft) long. Each mammoth had four working molar teeth at a time, and its teeth moved forward like a conveyor belt as they wore down.

Molar from Font de Champdamoy, France, Musée Georges-Garret (above), and diagram of the upper (occlusal) surface of a molar

Palaeobiology

Adult woolly mammoths could defend themselves from predators with their tusks, trunks, and size, but young and weakened animals were at risk from pack hunters such as wolves, cave hyenas, and large felines. Males may have used their tusks in fights over territory or mates, and showing off their tusks may have helped attract females. Their long tail hairs may have made the short tail useful as a flyswatter, like modern elephants. The sensitive trunk worked like a limb for handling objects and social contact, and the foot of the adult male "Yukagir mammoth" shows cracks in the soles that helped with grip. Like modern elephants, they were likely very social and lived in matriarchal (female-led) family groups. Trackways of a herd found at the St. Mary Reservoir in Canada, made 11,300–11,000 years ago, show almost equal numbers of adults, subadults, and juveniles. Dental enamel from Poland shows that they moved with the seasons, based on shifts in δ¹⁸O and ⁸⁷Sr/⁸⁶Sr, living in the south during winter and grazing the midlands in summer.

Woolly mammoths were well suited to the cold. They stored fat in their neck and withers, and their haemoglobin was adapted to cold, as in reindeer and musk oxen. Genetic studies, including one of the mitogenome, suggest adaptations to extreme environments. They ate mainly plants such as forbs, grasses, herbaceous plants, flowering plants, shrubs, mosses, and tree matter, and fossil dung (coprolites) suggests forbs dominated much of the last 50,000 years. An adult of 6 tonnes needed to eat 180 kg daily and may have foraged for up to 20 hours a day during the ice age (Quaternary glaciation). They picked buds and flowers, and some had dung fungus spores in their food. Isotope analysis shows they fed mainly on C₃ plants, and dental microwear shows they were mostly grazers. The calf Lyuba may have eaten faecal matter to build the intestinal microbes needed to digest plants, and young mammoths were weaned at about 2–3 years old. Tusk growth rings can show age, and mammoths may have lived about 60 years, like modern elephants. Males likely entered musth, a period of heightened aggressiveness, and produced temporin, a smelly oil; a 2023 study compared testosterone in tusk dentine. Health problems found in fossils include bone diseases, osteoarthritis, vertebrae damage from spondylitis, osteomyelitis, healed bone fractures, spondyloarthropathy, osteoporosis, parasitic flies, and protozoa. Distorted molars were the most common problem, and some teeth had periodontal disease, caries, or cancerous growths.

The woolly mammoth lived in a habitat called the mammoth steppe, or tundra steppe. This land stretched across northern Asia, parts of Europe, and northern North America during the last ice age. It was like the grassy steppes of modern Russia, but it had more kinds of plants, which were more plentiful and grew faster. Grasses, sedges, shrubs, and other herbaceous plants grew there, and scattered trees were mainly found in the south. The area was not mostly covered by ice and snow, as is often believed, because it is thought to have had high-pressure areas at that time. Other grazing animals, such as the woolly rhinoceros, wild horses, and bison, also lived there. Today, the Altai-Sayan assemblages, such as Khar-Us Nuur and Ukok-Sailiugem, are the biomes most similar to the mammoth steppe. A 2014 study found that forbs, a group of herbaceous plants, were more important in the steppe-tundra than earlier thought, and were a main food source for ice-age animals.

The southernmost woolly mammoth remains known come from Shandong province in China and are 33,000 years old. The southernmost European remains are from the Depression of Granada in Spain and are about the same age. DNA studies have helped scientists understand the phylogeography of the woolly mammoth. A 2008 DNA study showed two separate groups: one became extinct 45,000 years ago, and the other became extinct 12,000 years ago. These groups may be different enough to be called subspecies. The earlier group stayed in the middle of the high Arctic, while the later group had a much wider range. Woolly mammoths briefly spread into north-east Europe during the Younger Dryas age, and the mainland populations later died out. A 2008 genetic study suggested that some woolly mammoths that crossed the Bering land bridge into North America later moved back to Asia and replaced the earlier Asian population, not long before the species became extinct. Woolly mammoth and Columbian mammoth fossils have been found together in a few places in North America, including the Hot Springs sinkhole in South Dakota. It is unknown whether the two species lived there at the same time or whether woolly mammoths only moved into these southern areas when Columbian mammoths were absent.

Relationship with humans

Modern humans lived alongside woolly mammoths during the Upper Palaeolithic period, after they entered Europe from Africa between 30,000 and 40,000 years ago. Earlier, Neanderthals had lived alongside mammoths during the Middle Palaeolithic. Sites such as La Cotte de St Brelade in the Channel Islands, which dates to 200,000 years ago, show this. Neanderthals already used mammoth bones for tools and building materials. Woolly mammoths were very important to ice age humans, and in some areas human survival may have depended on them. This shared history was not recognised until the 19th century. In 1823, William Buckland published his discovery of the Red Lady of Paviland skeleton, which was found in a cave alongside woolly mammoth bones, but he wrongly denied that the two were from the same time. In 1864, Édouard Lartet found an engraving of a woolly mammoth on a piece of mammoth ivory in the Abri de la Madeleine cave in Dordogne, France. This was the first widely accepted proof that humans lived alongside prehistoric extinct animals. Woolly mammoths are also the third most depicted animal in ice age art, after horses and bison. More than 500 images of them have been found, including cave paintings in caves in Russia, France, and Spain, and carvings made from ivory, antler, stone, and bone, called "portable art." The French Rouffignac Cave has the most depictions, and other notable caves include the Chauvet Cave, Les Combarelles Cave, and Font-de-Gaume. Some images from the Cave of El Castillo may instead show the straight-tusked elephant.

Ice age people used woolly mammoth bones to build dwellings, both Neanderthals and modern humans. More than 70 such dwellings are known, mainly from the East European Plain. Large bones formed the foundations, and tusks were used for entrances. Woolly mammoth bones were also made into tools, furniture, and musical instruments, and ivory was carved into art objects, including several Venus figurines such as the Venus of Brassempouy, the Venus of Lespugue, and the Venus of Moravany. Other carvings include the Lion-man of Hohlenstein-Stadel, a female face from Dolní Věstonice, and the Swimming Reindeer. Woolly mammoths were also an important food source for both modern humans and Neanderthals, and some bones show signs of being butchered. Many mammoths may have been scavenged rather than hunted, and few specimens clearly show they were hunted. Hunters also used spear throwers shaped like woolly mammoths, and a boomerang and a perforated baton used for ropemaking have been found. At a site in southern Poland, stone spear points were found in mammoth bones, which suggests mammoths were a major prey. A Mousterian age specimen from Italy shows evidence of spear hunting by Neanderthals. Near the Yana River in Siberia, several specimens show signs of human hunting, but they seem to have been hunted mainly when ivory was needed. Two woolly mammoths from Wisconsin show signs of being butchered by Paleo-Indians.

Extinction

Most woolly mammoth populations disappeared during the late Pleistocene and mid-Holocene. This happened at the same time as most North American Pleistocene megafauna, including the Columbian mammoth, and as many steppe animals of Eurasia that lived alongside the mammoth, such as the woolly rhinoceros, cave lion, reindeer, saiga, Arctic fox, and steppe lemming. This was part of the Late Pleistocene extinctions, which began 40,000 years ago and peaked between 14,000 and 11,500 years ago. Scientists disagree about whether hunting or climate change, which shrank its habitat, was the main cause, or whether it was a mix of both. Evidence from δ¹⁸O values in tusks suggests that climate change was not the direct cause for Eurasian woolly mammoths. Large animals are generally more at risk than small ones because they have small populations and few young.

Climate patterns during the Last Interglacial suggest that woolly mammoths were sensitive to shrinking steppe-tundra habitats, since they were adapted to cold, dry, and open land. Their suitable habitat in Eurasia shrank during that warm period, which may have caused bottleneck effects that limited them to a few northern areas. When the climate became colder again, their populations recovered. The Last Glacial Period was when woolly mammoths spread the most, across most of Europe, northern Asia, and northern North America. Around 15,000 years ago, the mammoth steppe was replaced by wet tundra and forests across most of Siberia, which was poor habitat for them. Populations did not die out at the same time. Most disappeared between 14,000 and 10,000 years ago. Some of Europe's last mammoths lived in what is now Estonia, in the Puurmani area, and the youngest mainland fossils come from the Kyttyk Peninsula of Siberia, dated to 9,650 years ago. A small population survived on St. Paul Island, Alaska, until about 5,600 years ago. The last known fossil population stayed on Wrangel Island in the Arctic Ocean until 4,000 years ago, centuries after the dawn of human civilization and the building of the Great Pyramid and Sphinx of ancient Egypt. Studies using environmental DNA suggest that mammoths survived in the Yukon until about 5,700 years ago and on the Taymyr Peninsula of Siberia until 3,900 to 4,100 years ago, which may have been a refugium with drier habitat. However, old DNA in cold places can move into younger layers of soil, so these dates are uncertain.

DNA studies show two major population crashes. The first, around 280,000 years ago, was recovered from, but the second, about 12,000 years ago near the end of the ice age, was from which it did not recover. The Wrangel Island mammoths were cut off for 5,000 years by rising sea levels, and inbreeding in their small group led to a sharp loss of genetic variety. Their genetic evidence suggests a sudden end rather than a slow decline. Their genes had also built up many defects, which may fit the idea of genomic meltdown, though later research found this idea disputed. Their sudden disappearance may point to a sudden event, possibly related to climate, disease, or hunting. Mammoths in eastern Beringia, including modern Alaska and Yukon, died out about 13,300 years ago, roughly 1,000 years after people first arrived there. This matches the fate of other large animals of the Americas, such as gomphotheres. Climate change also shrank suitable mammoth habitat from 7,700,000 km² (3,000,000 sq mi) 42,000 years ago to 800,000 km² (310,000 sq mi) by 6,000 years ago, and mammoths lost even more habitat at the end of the Penultimate Glacial Period. A trackway in south-western Canada suggests that the species was already declining while living alongside humans. Some researchers think human hunting may have made populations smaller for thousands of years before the range collapsed.

Models of an adult and the calf "Dima" are shown in the State Museum of Natural History Stuttgart.

Further information: Revival of the woolly mammoth

Because soft tissue and DNA of woolly mammoths have been preserved, some people have proposed bringing the species back. One idea is cloning, which would place the DNA-containing nucleus of a mammoth into the egg cell of a female elephant. Another idea is artificially inseminating an elephant egg cell with sperm cells from a frozen mammoth, then breeding the hybrids over several generations. Some projects are replacing genes in elephant cells with mammoth genes using the CRISPR technique. By 2015, a team led by George Church had edited some mammoth genes into an Asian elephant, aiming first at cold resistance, such as ear size, fat, haemoglobin, and hair. Some researchers question the ethics of these attempts, since suitable habitat is limited, the species lived in groups, and resources might be better used to protect endangered elephants. In 2021, an Austin-based company raised funds to reintroduce the species in the Arctic tundra.

Fossil specimens

Further information: List of mammoth specimens

Woolly mammoth fossils have been found in many kinds of deposits, including old rivers and lakes and "Doggerland" in the North Sea, which was dry at times during the ice age. Most fossils are broken into pieces and contain no soft tissue. Some groups of bones, once called "elephants' graveyards", are thought to have formed when animals died near rivers and the streams gathered their bones together over thousands of years. Natural traps such as kettle holes, sink holes, and mud have also caught mammoths over time.

Apart from frozen remains, the only known soft tissue comes from a specimen preserved in a petroleum seep in Starunia, Poland. Most frozen remains have been found in northern Siberia and Alaska, mostly above the Arctic Circle, in permafrost. Many of the animals seem to have died in autumn, and some were swept away in rivers. In one spot by the Byoryolyokh River in Yakutia, more than 8,000 bones from at least 140 mammoths were found together. The first fully documented frozen specimen was found near the delta of the Lena River in 1799. In 1806, Michael Friedrich Adams recovered a skeleton and brought it to the Zoological Museum of the Zoological Institute of the Russian Academy of Sciences, where Wilhelm Gottlieb Tilesius mounted it. In 1901, the "Berezovka mammoth" was excavated near the Berezovka River, and it was transported to the Museum of Zoology in St. Petersburg. A calf nicknamed "Effie", found in 1948, is displayed at the American Museum of Natural History. In 1977, the frozen calf "Dima" was found near the Kolyma River, and Radiocarbon dating showed it died about 40,000 years ago. In 2007, the calf "Lyuba" was found near the Yuribey River, and its body may have been "pickled" by bacteria that produce lactic acid, which helped preserve it. In 2010, the juvenile "Yuka" was found, and in 2013, a well-preserved carcass was found on Maly Lyakhovsky Island in the New Siberian Islands. In 2022, a baby mammoth was found in the Klondike gold fields of Yukon, Canada, and was nicknamed "Nun cho ga," which means "big baby animal" in the Hän language.

Cultural significance

Woolly mammoths have remained culturally important long after their extinction. Indigenous peoples of Siberia found their remains and collected their tusks for the ivory trade. The Mansi and Khanty peoples saw mammoths as giant birds, and the Mansi, along with the Nenets, believed mammoths created mountains and lakes. In Evenk mythology, mammoths created the world by digging up land from the ocean floor with their tusks. The Selkup believed mammoths guarded the underworld, and the Yakuts regarded them as water spirits. North American Indigenous peoples used woolly mammoth ivory and bone for tools and art. The Bering Strait Inupiat believed the bones came from burrowing creatures. Some observers have connected legends from several Native American peoples to folk memory of extinct elephants, though other scholars doubt that such a memory could survive so long.

Woolly mammoth tusks were traded in Asia long before Europeans knew about them. Güyük, the 13th-century Khan of the Mongols, is reputed to have sat on a throne made from mammoth ivory. The 16th-century Chinese encyclopedia Ben Cao Gangmu described it as yin shu, "the hidden rodent." Europeans long interpreted the remains of extinct elephants as those of legendary creatures such as behemoths or giants, based on biblical accounts. Others thought they were modern elephants brought to Europe during the Roman Republic, such as the war elephants of Hannibal and Pyrrhus of Epirus. The ivory trade grew after Russia occupied Siberia, and from the 19th century, mammoth ivory became a highly prized material. Today it is still in demand as a replacement for banned elephant ivory and has been called "white gold." Trade in elephant ivory was largely banned after the 1989 Lausanne Conference. Since global warming thaws the permafrost, Siberian tusks have become easier to reach. Some people have also claimed that the woolly mammoth is not extinct and that small herds might survive in the tundra of the Northern Hemisphere. No scientific proof has ever been found for these claims, and the idea became part of the cryptozoology movement.