Extinct species of mammoth
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The woolly mammoth (Mammuthus primigenius) is an extinct species of mammoth that lived from the Middle Pleistocene until its extinction in the Holocene epoch. It was one of the last in a line of mammoth species, beginning with the African "Mammuthus subplanifrons" in the early Pliocene. The woolly mammoth began to diverge from the steppe mammoth about 800,000 years ago in Siberia. Its closest extant 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 had long been known in Asia before they became known to Europeans. The origin of these remains was long a matter of debate and often explained as being remains of legendary creatures. The mammoth was identified as an extinct species of elephant by Georges Cuvier in 1796.
The appearance and behaviour of this species are among the best studied of any prehistoric animal because of the discovery of frozen carcasses in Siberia and North America, as well as skeletons, teeth, stomach contents, dung, and depiction from life in prehistoric cave paintings. The woolly mammoth was roughly the same size as modern African elephants. Males reached shoulder heights between and weighed between . Females reached in shoulder heights and weighed between . A newborn calf weighed about . The woolly mammoth was well adapted to the cold environments present during glacial periods, including the last ice age. It was covered in fur, with an outer covering of long guard hairs and a shorter undercoat. The colour of the coat varied from dark to light. The ears and tail were short to minimise frostbite and heat loss. It had long, curved tusks and four molars, which were replaced six times during the lifetime of an individual. Its behaviour was similar to that of modern elephants, and it used its tusks and trunk for manipulating objects, fighting, and foraging. The diet of the woolly mammoth was mainly grasses and sedges. Individuals could probably reach the age of 60. Its habitat was the mammoth steppe, which stretched across northern Eurasia and North America.
The woolly mammoth coexisted with early humans, who used its bones and tusks for making art, tools, and dwellings, and hunted the species for food. The population of woolly mammoths declined at the end of the Late Pleistocene, with the last populations on mainland Siberia persisting until around 10,000 years ago, although isolated populations survived on St. Paul Island until 5,600 years ago and on Wrangel Island until 4,000 years ago. After its extinction, humans continued using its ivory as a raw material, a tradition that continues today. The completion of the mammoth genome project in 2015 sparked discussion about potentially reviving the woolly mammoth through several various methods. However, none of these approaches are currently feasible.
Taxonomy.
Remains of woolly mammoths were long known by native Siberians and Native Americans, who had various ways of interpreting them. Remains later reached other parts of Asia and Europe, where they were also interpreted in various ways prior to modern science. The first woolly mammoth remains studied by scientists were examined by the British physician Hans Sloane in 1728 and consisted of fossilised teeth and tusks from Siberia. Sloane was the first to recognise that the remains belonged to elephants. Sloane turned to another biblical explanation for the presence of elephants in the Arctic, asserting that they had been buried during the Great Flood, and that Siberia had previously been tropical before a drastic climate change. Others interpreted Sloane's conclusion slightly differently, arguing the flood had carried elephants from the tropics to the Arctic. Sloane's paper was based on travellers' descriptions and a few scattered bones collected in Siberia and Britain. He discussed the question of whether or not the remains were from elephants, but drew no conclusions. In 1738, the German zoologist Johann Philipp Breyne argued that mammoth fossils represented some kind of elephant. He could not explain why a tropical animal would be found in such a cold area as Siberia, and suggested that they might have been transported there by the Great Flood.
In 1796, French biologist Georges Cuvier was the first to identify the woolly mammoth remains not as modern elephants transported to the Arctic, but as an entirely new species. He argued this species had gone extinct and no longer existed, a concept that was not widely accepted at the time. Following Cuvier's identification, the German naturalist Johann Friedrich Blumenbach gave the woolly mammoth its scientific name, "Elephas primigenius", in 1799, placing it in the same genus as the Asian elephant ("Elephas maximus"). This name is Latin for "the first-born elephant". Cuvier coined the name "Elephas mammonteus" a few months later, but the former name was subsequently used. In 1828, the British naturalist Joshua Brookes used the name "Mammuthus borealis" for woolly mammoth fossils in his collection that he put up for sale, thereby coining a new genus name.
Where and how the word "mammoth" originated is unclear. According to the" Oxford English Dictionary", it comes from an old Vogul word "mēmoŋt", "earth-horn". It may be a version of "mehemot", the Arabic version of the biblical word "behemoth". Another possible origin is Estonian, where "maa" means "earth", and "mutt" means "mole". The word was first used in Europe during the early 17th century, when referring to "maimanto" tusks discovered in Siberia. The American president Thomas Jefferson, who had a keen interest in palaeontology, was partially responsible for transforming the word "mammoth" from a noun describing the prehistoric elephant to an adjective describing anything of surprisingly large size. The first recorded use of the word as an adjective was in a description of a wheel of cheese (the "Cheshire Mammoth Cheese") given to Jefferson 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, wherein he used various taxon names that had previously been proposed for mammoth species, including replacing "Mammuthus" with "Mammonteus", as he believed the former name to be invalidly published. Mammoth taxonomy was simplified by various researchers from the 1970s onwards, all species were retained in the genus "Mammuthus", and many proposed differences between species were instead interpreted as intraspecific variation.
Osborn chose two molars (found in Siberia and Osterode) from Blumenbach's collection at Göttingen University as the lectotype specimens for the woolly mammoth, since holotype designation was not practised in Blumenbach's time, and one of the specimens Blumenbach had described had been of the unrelated straight-tusked elephant ("Palaeoloxodon antiquus"). Soviet palaeontologist Vera Gromova further proposed the former should be considered the lectotype with the latter as paralectotype. Both molars were thought lost by the 1980s, and the more complete "Taimyr mammoth" found in Siberia in 1948 was therefore proposed as the neotype specimen in 1990. Resolutions to historical issues about the validity of the genus name "Mammuthus" and the type species designation of "E. primigenius" were also proposed. The paralectotype molar (specimen GZG.V.010.018) has since been located in the Göttingen University collection, identified by comparing it with Osborn's illustration of a cast.
Evolution.
The earliest known members of the Proboscidea, the clade, which contains modern elephants, existed about 55 million years ago around the Tethys Sea. The closest known relatives of the Proboscidea are the sirenians (dugongs and manatees) and the hyraxes (an order of small, herbivorous mammals). The family Elephantidae existed 6 million years ago in Africa and includes the modern elephants and the mammoths. Among many now-extinct clades, the mastodon ("Mammut") is only a distant relative of the mammoths and part of the separate family Mammutidae, which diverged 25 million years before the mammoths evolved. The Asian elephant is the closest extant relative of the mammoths. The following cladogram shows the placement of the woolly mammoth among Late Pleistocene and modern proboscideans, based on genetic data:
Within six weeks from 2005 to 2006, three teams of researchers independently assembled mitochondrial genome profiles of the woolly mammoth from ancient DNA, which allowed them to confirm the close evolutionary relationship between mammoths and Asian elephants ("Elephas maximus"). A 2015 DNA review confirmed Asian elephants as the closest living relative of the woolly mammoth. African elephants ("Loxodonta africana") branched away from this clade around 6 million years ago, close to the time of the similar split between chimpanzees and humans. A 2010 study confirmed these relationships and suggested the mammoth and Asian elephant lineages diverged 5.8–7.8 million years ago, while African elephants diverged from an earlier common ancestor 6.6–8.8 million years ago.
In 2008, much of the woolly mammoth's chromosomal DNA was mapped. The analysis showed that the woolly mammoth and the African elephant are 98.55% to 99.40% identical. The team mapped the woolly mammoth's nuclear genome sequence by extracting DNA from the hair follicles of both a 20,000-year-old mammoth retrieved from permafrost and another that died 60,000 years ago. In 2012, proteins were confidently identified for the first time, collected from a 43,000-year-old woolly mammoth.
Since many remains of each species of mammoth are known from several localities, reconstructing the evolutionary history of the genus through morphological studies is possible. Mammoth species can be identified from the number of enamel ridges (or lamellar plates) on their molars; primitive species had few ridges, and the number increased gradually as new species evolved to feed on more abrasive food items. The crowns of the teeth became deeper in height and the skulls became taller to accommodate this. At the same time, the skulls became shorter from front to back to minimise the weight of the head. The short and tall skulls of woolly and Columbian mammoths ("Mammuthus columbi") were the culmination of this process.
The first known members of the genus "Mammuthus" are the African species "Mammuthus subplanifrons" from the Pliocene, and "M. africanavus" from the Pleistocene. The former is thought to be the ancestor of later forms. Mammoths entered Europe around 3 million years ago. The earliest European mammoth has been named "M. rumanus"; it spread across Europe and China. Only its molars are known, which show that it had 8–10 enamel ridges. A population evolved 12–14 ridges, splitting off from and replacing the earlier type, becoming the southern mammoth ("M. meridionalis") about 2–1.7 million years ago. In turn, this species was replaced by the steppe mammoth ("M. trogontherii") with 18–20 ridges, which evolved in eastern Asia around 1 million years ago. Mammoths derived from "M. trogontherii" evolved molars with 26 ridges 400,000 years ago in Siberia and became the woolly mammoth. The earliest identified forms of woolly mammoth date to the Middle Pleistocene. Woolly mammoths entered North America about 100,000 years ago by crossing the Bering Strait.
Subspecies and hybridisation.
Individuals and populations showing transitional morphologies between each of the mammoth species are known, and primitive and derived species coexisted until the former disappeared. The different species and their intermediate forms have been termed "chronospecies". Many taxa intermediate between "M. primigenius" and other mammoths have been proposed, but their validity is uncertain; depending on author, they are either considered primitive forms of an advanced species or advanced forms of a primitive species. Distinguishing and determining these intermediate forms has been called one of the most long-lasting and complicated problems in Quaternary palaeontology. Regional and intermediate species and subspecies such as "M. intermedius", "M. chosaricus", "M. p. primigenius", "M. p. jatzkovi", "M. p. sibiricus", "M. p. fraasi", "M. p. leith-adamsi", "M. p. hydruntinus", "M. p. astensis", "M. p. americanus", "M. p. compressus", and "M. p. alaskensis" have been proposed.
A 2011 genetic study showed that two examined specimens of the Columbian mammoth were grouped within a subclade of woolly mammoths. This suggests that the two populations interbred and produced fertile offspring. A North American type formerly referred to as "M. jeffersonii" may be a hybrid between the two species. A 2015 study suggested that the animals in the range where "M. columbi" and "M. primigenius" overlapped formed a metapopulation of hybrids with varying morphology. It suggested that Eurasian "M. primigenius" had a similar relationship with "M. trogontherii" in areas where their range overlapped.
In 2021, DNA older than a million years was sequenced for the first time, from two mammoth teeth of Early Pleistocene age found in eastern Siberia. One tooth from Adycha (1–1.3 million years old) belonged to a lineage