Amammoth is any species of the extinctelephantidgenusMammuthus. They lived from the lateMiocene epoch (from around 6.2 million years ago) into theHolocene until about 4,000 years ago, with mammoth species at various times inhabiting Africa, Asia, Europe, and North America. Mammoths are distinguished from livingelephants by their (typically large) spirally twisted tusks and in some later species, the development of numerous adaptions to living in cold environments, including a thick layer of fur.
Mammoths andAsian elephants are more closely related to each other than they are toAfrican elephants. The oldest mammoth representative,Mammuthus subplanifrons, appeared around 6 million years ago during the late Miocene in what is now southern and Eastern Africa.[3] Later in thePliocene, by about three million years ago, mammoths dispersed into Eurasia, eventually covering most of Eurasia before migrating into North America around 1.5–1.3 million years ago, becoming ancestral to theColumbian mammoth (M. columbi). Thewoolly mammoth (M. primigenius) evolved about 700–400,000 years ago in Siberia, with some surviving on Russia'sWrangel Island in theArctic Ocean until as recently as 4,000 years ago, still extant during the existence of the earliest civilisations inancient Egypt andMesopotamia.
Etymology and early observations
According toThe American Heritage Dictionary, the word "mammoth" likely originates from *mān-oŋt, a word in theMansi languages of western Siberia meaning "earth horn", in reference to mammoth tusks.[4] Mammoths appear in the folkore of the indigenous people of Siberia, who were impressed by the great size of their remains. In the mythology of theEvenk people, mammoths were responsible for the creation of the world, digging up the land from the ocean floor with their tusks. TheSelkup believed that mammoths lived underground and guarded theunderworld, while theNenets and theMansi (the latter of whom, along with theKhanty, conceived mammoths as giant birds) believed that mammoths were responsible for the creation of mountains and lakes, while theYakuts regarded mammoths as water spirits.[5]
The wordmammoth was first used in Europe during the early 17th century, when referring tomaimanto tusks discovered in Siberia,[6] as recorded in the 1618 edition of theDictionariolum Russico-Anglicum.[7] The earliest scientific research paper on mammoths was byVasily Tatishchev in 1725.[5]John Bell, who was on theOb River in 1722, said that mammoth tusks were well known in the area. They were called "mammon's horn" and were often found in washed-out river banks. Bell bought one and presented it toHans Sloan who pronounced it an elephant's tooth.[8]
In theAmerican colonies around 1725, enslaved Africans digging in the vicinity of theStono River inSouth Carolina unearthed molar teeth recognised in modern times to belong toColumbian mammoths, with the remains subsequently examined by the British naturalistMark Catesby, who visited the site, and later published an account of his visit in 1843. While the slave owners were puzzled by the objects and suggested that they originated from thegreat flood described in the Bible, Catesby noted that the slaves unanimously agreed that the objects were the teeth of elephants similar to those from their African homeland, to which Catesby concurred, marking the first technical identification of any fossil animal in North America.[9][10]
In 1796,French biologistGeorges Cuvier was the first to identifywoolly mammoth remains not as modern elephants transported to the Arctic, but as an entirely new species. He argued this species had goneextinct and no longer existed, a concept that was not widely accepted at the time.[11][12] Following Cuvier's identification, German naturalistJohann Friedrich Blumenbach gave the woolly mammoth its scientific name,Elephas primigenius, in 1799, placing it in theElephas, thegenus which today contains theAsian elephant (Elephas maximus). Originally the African elephants, as well as theAmerican mastodon (described in 1792) were also placed inElephas. Cuvier coined thesynonymElephas mammonteus for the woolly mammoth a few months later, butE. primigenius became the widely used name for the species, including by Cuvier.[13] The genus nameMammuthus was coined by British anatomistJoshua Brookes in 1828, as part of a survey of his museum collection.[14]
Thomas Jefferson, who famously had a keen interest inpaleontology, is partially responsible for transforming the wordmammoth 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 large wheel of cheese (the "Cheshire Mammoth Cheese") given to Jefferson in 1802.[15]
Evolution
The earliest knownproboscideans, theclade that contains the elephants, arose about 55 million years ago on the landmass of Afro-Arabia. The closest relatives of the Proboscidea are thesirenians and thehyraxes. The familyElephantidae arose a million years ago in Africa, including the living elephants and mammoths. Among many now-extinct clades, themastodon is only a distant relative of the mammoths and part of the separateMammutidae family, which diverged 25 million years before the mammoths evolved.[16]
Following the publication of the woolly mammothsmitochondrial genome sequence in 1997, it has since become widely accepted that mammoths andAsian elephants share a closer relationship with each other than either do toAfrican elephants.[17][18]
The followingcladogram shows the placement of the genusMammuthus among other proboscideans, based onhyoid characteristics and genetics:[19][18]
It is possible to reconstruct the evolutionary history of the genus through morphological studies. Mammoth species can be identified from the number of enamel ridges/lamellae on their molars; the primitive species had few ridges, which increased gradually as new species evolved and replaced the former ones. At the same time, the crowns of the teeth became longer, and the skulls became higher from top to bottom and shorter from the back to the front over time to accommodate this.[20]
The earliest mammoths, assigned to the speciesMammuthus subplanifrons, are known from southern and eastern Africa, with the earliest records dating to the LateMiocene, around 6.2–5.3 million years ago.[3] By the LatePliocene, mammoths had become confined to the northern portions of the African continent with remains from this time assigned toMammuthus africanavus.[21] During the Late Pliocene, by 3.2 million years ago, mammoths dispersed into Eurasia via the Sinai Peninsula. The earliest mammoths in Eurasia are assigned to the speciesMammuthus rumanus.[22] The youngest remains of mammoths in Africa are from Aïn Boucherit, Algeria dating to the Early Pleistocene, around 2.3–2 million years ago (with a possible later record from Aïn Hanech, Algeria, dating to 1.95–1.78 million years ago).[21]
Mammuthus rumanus is thought to be the ancestor ofMammuthus meridionalis, which first appeared at the beginning of the Pleistocene, around 2.6 million years ago.[23]Mammuthus meridionalis subsequently gave rise toMammuthus trogontherii (the steppe mammoth) in Eastern Asia around 1.7 million years ago. Around 1.5–1.3 million years ago,M. trogontherii crossed theBering Land Bridge into North America, becoming ancestral toMammuthus columbi (the Columbian mammoth).[24] At the end of the Early PleistoceneMammuthus trogontherii migrated into Europe, replacingM. meridionalis around 1–0.8 million years ago.[23]Mammuthus primigenius (the woolly mammoth) had evolved fromM. trogontherii in Siberia by around 600,000–500,000 years ago, replacingM. trogontherii in Europe by around 200,000 years ago, and migrated into North America during the Late Pleistocene.[25]
Like living elephants, mammoths typically had large body sizes. The largest known species likeMammuthus meridionalis andMammuthus trogontherii (the steppe mammoth) were considerably larger than modern elephants, with mature adult males having an average height of approximately 3.8–4.2 m (12.5–13.8 ft) at the shoulder and weights of 9.6–12.7tonnes (21,000–28,000 lb), while exceptionally large males may have reached 4.5 m (14.8 ft) at the shoulder and 14.3 tonnes (31,526.1 lb) in weight.[29] However, woolly mammoths were considerably smaller, only about as large as modernAfrican bush elephants with males around 2.80–3.15 m (9 ft 2.2 in – 10 ft 4.0 in) high at the shoulder, and 4.5–6tonnes (9,900–13,200 lb) in weight on average,[30] with the largest recorded individuals being around 3.5 m (11.5 ft) tall and 8.2 tonnes (18,077.9 lb) in weight.[29] The insular dwarf mammoth species were considerably smaller, with the smallest speciesM. creticus estimated to have a shoulder height of only around 1 metre (3.3 ft) and a weight of about 180 kilograms (400 lb), making it one of the smallest elephantids known.[29]
Woolly mammoths (M. primigenius), including one of the largest, the Siegsdorf mammoth (left, around 3.5 metres (11 ft) tall), and a mature Siberian bull (around 2.7 metres (8.9 ft) metres tall)
The number oflamellae (ridge-like structures) on the molars, particularly on the third molars, substantially increased over the course of mammoth evolution. The earliest Eurasian speciesM. rumanus have around 8-10 lamellae on the third molars,[31] while Late Pleistocene woolly mammoths have 20-28 lamellae on the third molars. These changes also corresponded with reduced enamel thickness and increasing tooth height (hypsodonty).[25] These changes are thought to be adaptations to increasing abrasion resulting from the shift in the diet of mammoths from abrowsing based diet inM. rumanus, towards agrazing diet in later species.[32][33]
Molars
Cross section through elephantid molars, showing their internal structure
Both sexes bore tusks. A first, small set appeared at about the age of six months, and these were replaced at about 18 months by the permanent set. Growth of the permanent set was at a rate of about 2.5 to 15.2 cm (1 to 6 in) per year.[34] The tusks display a strong spiral twisting.[35] Mammoth tusks are among the largest known among proboscideans with some specimens over 4 m (13.1 ft) in length and likely 200 kg (440.9 lb) in weight with some historical reports suggesting tusks ofColumbian mammoths could reach lengths of around 5 m (16.4 ft) substantially surpassing the largest known modern elephant tusks.[36]
The heads of mammoths were prominently domed.[37] The first severalthoracic vertebrae of mammoths typically had long neural spines.[38] The back was typically sloping, with the body being wider than that of African elephants. The tails of mammoths were relatively short compared to living elephants.[37]
Life restoration of a woolly mammoth at Royal BC Museum
While early mammoth species likeM. meridionalis were probably relatively hairless, similar to modern elephants,[39]M. primigenius and likelyM. trogontherii had a substantial coat of fur, among other physiological adaptations for living in cold environments. Genetic sequencing ofM. trogontherii-like mammoths, over 1 million years old from Siberia suggests that they had already developed many of the genetic changes found in woolly mammoths responsible for tolerance of cold conditions.[40] Scientists discovered and studied the remains of a mammoth calf, and found that fat greatly influenced its form, and enabled it to store large amounts of nutrients necessary for survival in temperatures as low as −50 °C (−58 °F).[41] The fat also allowed the mammoths to increase their muscle mass, allowing the mammoths to fight against enemies and live longer.[42] Woolly mammoths evolved a suite of adaptations for arctic life, including morphological traits such as small ears and tails to minimize heat loss, a thick layer of subcutaneous fat, and numerous sebaceous glands for insulation, as well as a large brown-fat hump like deposit behind the neck that may have functioned as a heat source and fat reservoir during winter.[43]
Based on studies of their close relatives, the modern elephants and mammoths probably had agestation period of 22 months, resulting in a single calf being born. Their social structure was probably the same as that of living elephants, with females and juveniles residing in herds headed by a matriarch, whilst bulls lived solitary lives or formed loose groups after sexual maturity,[44] with analysis of testosterone levels in tusks indicating that adult males experienced periods ofmusth like modern elephants, where they entered a state of heightened aggression.[45]
The earliest mammoth species likeM. subplanifrons andM. rumanus were mixed feeders (bothbrowsing andgrazing) to browsers. Throughout mammoth evolution in Eurasia, their diet shifted towards mixed feeding-grazing inM. trogontherii, culminating in the woolly mammoth, which was largely a grazer, with stomach contents of woolly mammoths suggesting that they largely fed on grass andforbs.M. columbi is thought to have been a mixed feeder.[33]
Like living elephants, mammoth adults may have been largely invulnerable to non-human predation,[46] though evidence has been found for the hunting of mammoth calves by predators, such as by thescimitar-toothed cat (Homotherium).[47]
In living proboscideans, broken tusks sometimes occur during, for example, fights between males or when elephants of both sexes shove each other to reach critical resources such as water. The fracture surface of the remaining (rooted) tooth then becomes smoothed from use. It is very likely that this also occurred in extinct proboscideans such as mammoths as seen from a tusk found at Fenstanton Gravels (Cambs, UK) which still had some of the outer layers of cementum preserved and had a smooth, polished surface on an old, fractured surface ('faceting').[48]
Evidence that humans interacted with mammoths extends back to around 1.8 million years ago, with a number of bones ofMammuthus meridionalis from theDmanisi site in Georgia having marks suggested to be the result of butchery byarchaic humans, likely as a result of scavenging.[49] During theLast Glacial Period, modern humans hunted woolly mammoths,[50] used their remains to create art and tools,[51][50] and depicted them in works of art.[51] Remains of Columbian mammoths at a number of sites suggest that they were hunted byPaleoindians, the first humans to inhabit the Americas.[52] A possible bone engraving of a Columbian mammoth made by Paleoindians is known from Vero Beach, Florida.[53]
Upper Paleolithic painting of woolly mammoth fromRouffignac Cave, France
Probable engraving of a Columbian mammoth from Vero Beach, Florida
Following the end of theLast Glacial Maximum, the range of the woolly mammoth began to contract, disappearing from most of Europe by 14,000 years ago.[54] By theYounger Dryas (around 12,900-11,700 yearsBefore Present), woolly mammoths were confined to the northernmost regions of Siberia. This contraction is suggested to have been caused by the warming induced expansion of unfavourable wettundra and forest environments at the expense of the preferred dry openmammoth steppe, with the possible additional pressure of human hunting. The last woolly mammoths in mainland Siberia became extinct around 10,000 years ago, during the earlyHolocene.[55] The final extinction of mainland woolly mammoths may have been driven by human hunting.[54]Relict populations survived onSaint Paul island in the Bering Strait until around 5,600 years ago, with their extinction likely due to the degradation of freshwater sources,[56] and onWrangel Island off the coast of Northeast Siberia until around 4,000 years ago.[55]
The last reliable dates of the Columbian mammoth date to around 12,500 years ago.[57] Columbian mammoths became extinct as part of theend-Pleistocene extinction event where most large mammals across the Americas became extinct approximately simultaneously at the end of the Late Pleistocene.[58] Hunting of Columbian mammoths by Paleoindians may have been a contributory factor in their extinction.[52] The timing of the extinction of the dwarf Sardinian mammothMammuthus lamarmorai is difficult to constrain precisely, though the youngest specimen likely dates to sometime around 57–29,000 years ago.[59] The youngest records of thepygmy mammoth (Mammuthus exillis) date to around 13,000 years ago, coinciding with the reducing of the area of the Californian Channel Islands as a result of rising sea level, the earliest known humans in the Channel Islands, and climatic change resulting in the decline of the previously dominant conifer forest ecosystems and expansion of scrub and grassland.[60]
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