Woolly mammoths

The woolly mammoth (''Mammuthus primigenius'') is an extinct species of mammoth that lived during the Pleistocene until its extinction in the Holocene epoch. It was one of the last in a line of mammoth species, beginning with ''Mammuthus subplanifrons'' in the early Pliocene about 800,000 years ago in East Asia. Its closest extant relative is the Asian elephant. DNA studies show that the Columbian mammoth was a hybrid between woolly mammoths and another lineage descended from steppe mammoths. 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. Mammoth remains had long been known in Asia before they became known to Europeans in the 17th century. 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 woolly mammoth was roughly the same size as modern African elephants. Males reached shoulder heights between and weighed up to . Females reached in shoulder heights and weighed up to . A newborn calf weighed about . The woolly mammoth was well adapted to the cold environment during 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 Pleistocene, disappearing throughout most of its mainland range, although isolated populations survived on St. Paul Island until 5,600 years ago, on Wrangel Island until 4,000 years ago, and possibly (based on ancient eDNA) in the Yukon up to 5,700 years ago and on the Taymyr Peninsula up to 3,900 years ago. After its extinction, humans continued using its ivory as a raw material, a tradition that continues today. With a genome project for the mammoth completed in 2015, it has been proposed the species could be revived through various means, but none of the methods proposed are yet feasible.

Taxonomy

Remains of various extinct elephants were known by Europeans for centuries, but were generally interpreted, based on biblical accounts, as the remains of legendary creatures such as behemoths or giants. They were thought to be remains of modern elephants that had been brought to Europe during the Roman Republic, for example the war elephants of Hannibal and Pyrrhus of Epirus, or animals that had wandered north. The first woolly mammoth remains studied by European scientists were examined by 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, 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. 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. 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.Simpson, J. (2009).
Word Stories: Mammoth
." ''Oxford English Dictionary Online'', Oxford University Press. Accessed 5 June 2009.

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. 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 following cladogram shows the placement of the genus ''Mammuthus'' among other proboscideans, based on characteristics of the hyoid bone in the neck:

Within six weeks from 2005-2006, 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

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