A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage or marine algae, for the main component of its diet. As a result of their plant diet, herbivorous animals have mouthparts adapted to rasping or grinding. Horses and other herbivores have wide flat teeth that are adapted to grinding grass, tree bark, other tough plant material. A large percentage of herbivores have mutualistic gut flora that help them digest plant matter, more difficult to digest than animal prey; this flora is made up of cellulose-digesting bacteria. Herbivore is the anglicized form of a modern Latin coinage, cited in Charles Lyell's 1830 Principles of Geology. Richard Owen employed the anglicized term in an 1854 work on fossil skeletons. Herbivora is derived from the Latin herba meaning a small plant or herb, vora, from vorare, to eat or devour. Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants and photosynthesizing bacteria.
More organisms that feed on autotrophs in general are known as primary consumers. Herbivory is limited to animals that eat plants. Fungi and protists that feed on living plants are termed plant pathogens, while fungi and microbes that feed on dead plants are described as saprotrophs. Flowering plants that obtain nutrition from other living plants are termed parasitic plants. There is, however, no single exclusive and definitive ecological classification of consumption patterns. In zoology, an herbivore is an animal, adapted to eat plant matter. Our understanding of herbivory in geological time comes from three sources: fossilized plants, which may preserve evidence of defence, or herbivory-related damage. Although herbivory was long thought to be a Mesozoic phenomenon, fossils have shown that within less than 20 million years after the first land plants evolved, plants were being consumed by arthropods. Insects fed on the spores of early Devonian plants, the Rhynie chert provides evidence that organisms fed on plants using a "pierce and suck" technique.
During the next 75 million years, plants evolved a range of more complex organs, such as roots and seeds. There is no evidence of any organism being fed upon until the middle-late Mississippian, 330.9 million years ago. There was a gap of 50 to 100 million years between the time each organ evolved and the time organisms evolved to feed upon them. Further than their arthropod status, the identity of these early herbivores is uncertain. Hole feeding and skeletonisation are recorded in the early Permian, with surface fluid feeding evolving by the end of that period. Herbivory among four-limbed terrestrial vertebrates, the tetrapods developed in the Late Carboniferous. Early tetrapods were large amphibious piscivores. While amphibians continued to feed on fish and insects, some reptiles began exploring two new food types and plants; the entire dinosaur order ornithischia was composed with herbivores dinosaurs. Carnivory was a natural transition from insectivory for medium and large tetrapods, requiring minimal adaptation.
In contrast, a complex set of adaptations was necessary for feeding on fibrous plant materials. Arthropods evolved herbivory in four phases, changing their approach to it in response to changing plant communities. Tetrapod herbivores made their first appearance in the fossil record of their jaws near the Permio-Carboniferous boundary 300 million years ago; the earliest evidence of their herbivory has been attributed to dental occlusion, the process in which teeth from the upper jaw come in contact with teeth in the lower jaw is present. The evolution of dental occlusion led to a drastic increase in plant food processing and provides evidence about feeding strategies based on tooth wear patterns. Examination of phylogenetic frameworks of tooth and jaw morphologes has revealed that dental occlusion developed independently in several lineages tetrapod herbivores; this suggests that evolution and spread occurred within various lineages. Herbivores form an important link in the food chain because they consume plants in order to digest the carbohydrates photosynthetically produced by a plant.
Carnivores in turn consume herbivores for the same reason, while omnivores can obtain their nutrients from either plants or animals. Due to a herbivore's ability to survive on tough and fibrous plant matter, they are termed the primary consumers in the food cycle. Herbivory and omnivory can be regarded as special cases of Consumer-Resource Systems. Herbivores come in all sizes in the animal kingdom, they include aquatic and non-aquatic vertebrates. They can be large, like an elephant. Many herbivores found living in close proximity to humans, such as rodents, cows and camels. Two herbivore feeding strategies are browsing. For a terrestrial mammal to be called a grazer, at least 90% of the forage has to be grass, for a browser at least 90% tree leaves and/or twigs. An intermediate feeding strategy is called "mixed-feeding". In their daily need to take up energy from forage, herbivores of different body mass may be selective in choosing their food. "Selective" means that herbivores may choose their forage source depending on, e.g. season or food avail
The Devonian is a geologic period and system of the Paleozoic, spanning 60 million years from the end of the Silurian, 419.2 million years ago, to the beginning of the Carboniferous, 358.9 Mya. It is named after Devon, where rocks from this period were first studied; the first significant adaptive radiation of life on dry land occurred during the Devonian. Free-sporing vascular plants began to spread across dry land, forming extensive forests which covered the continents. By the middle of the Devonian, several groups of plants had evolved leaves and true roots, by the end of the period the first seed-bearing plants appeared. Various terrestrial arthropods became well-established. Fish reached substantial diversity during this time, leading the Devonian to be dubbed the "Age of Fishes." The first ray-finned and lobe-finned bony fish appeared, while the placoderms began dominating every known aquatic environment. The ancestors of all four-limbed vertebrates began adapting to walking on land, as their strong pectoral and pelvic fins evolved into legs.
In the oceans, primitive sharks became more numerous than in the Late Ordovician. The first ammonites, species of molluscs, appeared. Trilobites, the mollusc-like brachiopods and the great coral reefs, were still common; the Late Devonian extinction which started about 375 million years ago affected marine life, killing off all placodermi, all trilobites, save for a few species of the order Proetida. The palaeogeography was dominated by the supercontinent of Gondwana to the south, the continent of Siberia to the north, the early formation of the small continent of Euramerica in between; the period is named after Devon, a county in southwestern England, where a controversial argument in the 1830s over the age and structure of the rocks found distributed throughout the county was resolved by the definition of the Devonian period in the geological timescale. The Great Devonian Controversy was a long period of vigorous argument and counter-argument between the main protagonists of Roderick Murchison with Adam Sedgwick against Henry De la Beche supported by George Bellas Greenough.
Murchison and Sedgwick named the period they proposed as the Devonian System. While the rock beds that define the start and end of the Devonian period are well identified, the exact dates are uncertain. According to the International Commission on Stratigraphy, the Devonian extends from the end of the Silurian 419.2 Mya, to the beginning of the Carboniferous 358.9 Mya. In nineteenth-century texts the Devonian has been called the "Old Red Age", after the red and brown terrestrial deposits known in the United Kingdom as the Old Red Sandstone in which early fossil discoveries were found. Another common term is "Age of the Fishes", referring to the evolution of several major groups of fish that took place during the period. Older literature on the Anglo-Welsh basin divides it into the Downtonian, Dittonian and Farlovian stages, the latter three of which are placed in the Devonian; the Devonian has erroneously been characterised as a "greenhouse age", due to sampling bias: most of the early Devonian-age discoveries came from the strata of western Europe and eastern North America, which at the time straddled the Equator as part of the supercontinent of Euramerica where fossil signatures of widespread reefs indicate tropical climates that were warm and moderately humid but in fact the climate in the Devonian differed during its epochs and between geographic regions.
For example, during the Early Devonian, arid conditions were prevalent through much of the world including Siberia, North America, China, but Africa and South America had a warm temperate climate. In the Late Devonian, by contrast, arid conditions were less prevalent across the world and temperate climates were more common; the Devonian Period is formally broken into Early and Late subdivisions. The rocks corresponding to those epochs are referred to as belonging to the Lower and Upper parts of the Devonian System. Early DevonianThe Early Devonian lasted from 419.2 ± 2.8 to 393.3 ± 2.5 and began with the Lochkovian stage, which lasted until the Pragian. It spanned from 410.8 ± 2.8 to 407.6 ± 2.5, was followed by the Emsian, which lasted until the Middle Devonian began, 393.3± 2.7 million years ago. During this time, the first ammonoids appeared. Ammonoids during this time period differed little from their nautiloid counterparts; these ammonoids belong to the order Agoniatitida, which in epochs evolved to new ammonoid orders, for example Goniatitida and Clymeniida.
This class of cephalopod molluscs would dominate the marine fauna until the beginning of the Mesozoic era. Middle DevonianThe Middle Devonian comprised two subdivisions: first the Eifelian, which gave way to the Givetian 387.7± 2.7 million years ago. During this time the jawless agnathan fishes began to decline in diversity in freshwater and marine environments due to drastic environmental changes and due to the increasing competition and diversity of jawed fishes; the shallow, oxygen-depleted waters of Devonian inland lakes, surrounded by primitive plants, provided the environment necessary for certain early fish to develop such essential characteristics as well developed lungs, the ability to crawl out of the water and onto the land for short periods of time. Late DevonianFinally, the Late Devonian started with the Frasnian, 382.7 ± 2.8 to 372.2 ± 2.5, during which the first forests took shape on land. The first tetrapods appeared in the fossil record in the ensuing Famennian subdivisi
Tylopoda is a suborder of terrestrial herbivorous even-toed ungulates belonging to the order Artiodactyla. They are found in the wild in their native ranges of South America and Asia, while Australian feral camels are introduced; the group has a long fossil history in North Europe. Tylopoda appeared during the Eocene around 46.2 million years ago. Tylopoda has only one extant family, which includes camels, guanacos and vicuñas; this group was much more diverse in the past, containing a number of extinct families in addition to the ancestors of living camelids. Tylopods are not ruminants. Tylopoda was considered monophyletic by Matthew, it was treated as an unranked clade by Matthew and as a suborder by Carroll, Ursing et al. and Whistler and Webb. It was assigned to Ruminantia by Matthew; the main problem with circumscription of Tylopoda is that the extensive fossil record of camel-like mammals has not yet been examined from a cladistic standpoint. Tylopoda is a distinctive lineage among the artiodactyls, but its exact relationships are somewhat elusive because the six living species are all related and can be considered "living fossils", the sole surviving lineage of a prehistorically wildly successful radiation.
More recent studies suggest that tylopods are not as related to ruminants as traditionally believed, expressed in cladogram form as: The position of cetaceans with regard to Tylopoda poses a central problem. While a close relationship between these and ungulates had been proposed by Frank Evers Beddard in 1900, is accepted today, cetaceans have diverged so radically from their ancestors' lifestyle as to confound analyses of fossils and even DNA. Tylopoda, on the other hand, are conservative in their lifestyle and seem to have occupied the same ecological niche since their origin over 40 million years ago. Thus, it seems that the previous assumption of a close relationship between Tylopoda and ruminants is because all other close relatives are so divergent in their adaptations as to have obscured most indications of relationship, or at least those visible to phenetic analyses. However, the rather basal position that Tylopoda appears to have among the even-toed ungulates and relatives means that the oldest members of this lineage are still morphologically primitive and hard to distinguish from the ancestors of related lineages.
The first major modern and comprehensive analysis of the problem supported this. The taxa assigned to Tylopoda are:Basal and incertae sedis Genus †Gobiohyus? Family †HomacodontidaeSuperfamily †Anoplotherioidea Family †Anoplotheriidae Family †Cainotheriidae Family †DacrytheriidaeSuperfamily Cameloidea Family †Oromerycidae Family CamelidaeSuperfamily †Merycoidodontoidea Family †"Agriochoeridae" Family †MerycoidodontidaeSuperfamily †Xiphodontoidea Family †Xiphodontidae Several additional prehistoric artiodactyl taxa are sometimes assigned to the Tylopoda, but other authors consider them incertae sedis or basal lineages among the artiodactyla: Family †Antiacodontidae Family †Choeropotamidae Family †"Diacodexeidae" Family †LeptochoeridaeThe Cebochoeridae and Protoceratidae, on the other hand, are prehistoric families that were placed within Tylopoda in the past, but are now considered more related to cetaceans and ruminants than to camels
A pig is any of the animals in the genus Sus, within the even-toed ungulate family Suidae. Pigs include the domestic pig and its ancestor, the common Eurasian wild boar, along with other species. Related creatures outside the genus include the peccary, the babirusa, the warthog. Pigs, like all suids, are native to the African continents. Juvenile pigs are known as piglets. Pigs are social and intelligent animals. With around 1 billion individuals alive at any time, the domestic pig is among the most populous large mammals in the world. Pigs can consume a wide range of food. Pigs are biologically similar to humans and are thus used for human medical research; the Online Etymology Dictionary provides anecdotal evidence as well as linguistic, saying that the term derives from Old English *picg, found in compounds, ultimate origin unknown. "young pig". Related to Low German bigge, Dutch big.... Another Old English word for "pig" was fearh, related to furh "furrow," from PIE *perk- "dig, furrow". "This reflects a widespread IE tendency to name animals from typical attributes or activities".
Synonyms grunter, oinker are from sailors' and fishermen's euphemistic avoidance of uttering the word pig at sea, a superstition based on the fate of the Gadarene swine, who drowned. The Online Etymology Dictionary traces the evolution of sow, the term for a female pig, through various historical languages: Old English sugu, su "female of the swine," from Proto-Germanic *su-, from PIE root *su- imitative of pig noise, it is likely that the word to call pigs, "soo-ie," is derived. An adjectival form is porcine. Another adjectival form is suine. A typical pig has a large head with a long snout, strengthened by a special prenasal bone and by a disk of cartilage at the tip; the snout is used to dig into the soil to find food and is a acute sense organ. There are four hoofed toes on each foot, with the two larger central toes bearing most of the weight, but the outer two being used in soft ground; the dental formula of adult pigs is 188.8.131.52.1.4.3. The rear teeth are adapted for crushing. In the male, the canine teeth form tusks, which grow continuously and are sharpened by being ground against each other.
Captive mother pigs may savage their own piglets if they become stressed. Some attacks on newborn piglets are non-fatal. Others may cause the death of the piglets and sometimes, the mother may eat the piglets, it is estimated that 50% of piglet fatalities are due to the mother attacking, or unintentionally crushing, the newborn pre-weaned animals. With around 1 billion individuals alive at any time, the domestic pig is one of the most numerous large mammals on the planet; the ancestor of the domestic pig is the wild boar, one of the most numerous and widespread large mammals. Its many subspecies are native to all but the harshest climates of continental Eurasia and its islands and Africa as well, from Ireland and India to Japan and north to Siberia. Long isolated from other pigs on the many islands of Indonesia and the Philippines, pigs have evolved into many different species, including wild boar, bearded pigs, warty pigs. Humans have introduced pigs into Australia and South America, numerous islands, either accidentally as escaped domestic pigs which have gone feral, or as wild boar.
The wild pig can take advantage of any forage resources. Therefore, it can live in any productive habitat that can provide enough water to sustain large mammals such as pigs. If there is increased foraging of wild pigs in certain areas, it can cause a nutritional shortage which can cause the pig population to decrease. If the nutritional state returns to normal, the pig population will most rise due to the pigs' increased reproduction rate. Pigs are omnivores, which means that they consume both animals. In the wild, they are foraging animals eating leaves, roots and flowers, in addition to some insects and fish; as livestock, pigs are fed corn and soybean meal with a mixture of vitamins and minerals added to the diet. Traditionally, they were raised on dairy farms and called "mortgage lifters", due to their ability to use the excess milk as well as whey from cheese and butter making combined with pasture. Older pigs will consume three to five gallons of water per day; when kept as pets, the optimal healthy diet consists of a balanced diet of raw vegetables, although some may give their pigs conventional mini pig pellet feed.
Domesticated pigs miniature breeds, are kept as pets. Domestic pigs are raised commercially as livestock; because of their foraging abilities and excellent sense of smell, they are used to find truffles in many European countries. Both wild and feral pigs are hunted; the short, coarse hairs of the pig are called brist
The molars or molar teeth are large, flat teeth at the back of the mouth. They are more developed in mammals, they are used to grind food during chewing. The name molar derives from Latin, molaris dens, meaning "millstone tooth", from mola and dens, tooth. Molars show a great deal of diversity in shape across mammal groups. In humans, the molar teeth have either five cusps. Adult humans have 12 molars, in four groups of three at the back of the mouth; the third, rearmost molar in each group is called a wisdom tooth. It is the last tooth to appear, breaking through the front of the gum at about the age of 20, although this varies from individual to individual. Race can affect the age at which this occurs, with statistical variations between groups. In some cases, it may not erupt at all; the human mouth contains lower molars. They are: maxillary first molar, maxillary second molar, maxillary third molar, mandibular first molar, mandibular second molar, mandibular third molar. In mammals, the crown of the molars and premolars is folded into a wide range of complex shapes.
The basic elements of the crown are the more or less conical projections called cusps and the valleys that separate them. The cusps contain both dentine and enamel, whereas minor projections on the crown, called crenullations, are the result of different enamel thickness. Cusps are joined to form ridges and expanded to form crests. Cingula are incomplete ridges that pass around the base of the crown; these mammalian, multicusped cheek teeth evolved from single-cusped teeth in reptilians, although the diversity of therapsid molar patterns and the complexity in the molars of the earliest mammals make determining how this happened impossible. According to the accepted "differentiation theory", additional cusps have arisen by budding or outgrowth from the crown, while the rivalling "concrescence theory" instead proposes that complex teeth evolved by the clustering of separate conical teeth. Therian mammals are agreed to have evolved from an ancestor with tribosphenic cheek teeth, with three main cusps arranged in a triangle.
Each major cusp on an upper molar is called a cone and is identified by a prefix dependent on its relative location on the tooth: proto-, para-, meta-, hypo-, ento-. Suffixes are added to these names: -id is added to cusps on a lower molar. A shelf-like ridge on the lower part of the crown is called a cingulum; the design, considered one of the most important characteristics of mammals is a three-cusped shape called a tribosphenic molar. This molar design has two important features: the trigonid, or shearing end, the talonid, or crushing heel. In modern tribosphenic molars, the trigonid is towards the front of the jaw and the talonid is towards the rear; the tribosphenic tooth is found in young platypuses. Upper molars look like three-pointed mountain ranges; the tribosphenic design appears primitively in all groups of mammals. Some paleontologists believe that it developed independently in monotremes, rather than being inherited from an ancestor that they share with marsupials and placentals. For example, the dentition of the Early Cretaceous monotreme Steropodon is similar to those of Peramus and dryolestoids, which suggests that monotremes are related to some pre-tribosphenic therian mammals, but, on the other hand, the status of neither of these two groups is well-established.
Some Jurassic mammals, such as Shuotherium and Pseudotribos, have "reversed tribosphenic" molars, in which the talonid is towards the front. This variant is regarded as an example of convergent evolution. From the primitive tribosphenic tooth, molars have diversified into several unique morphologies. In many groups, a fourth cusp, the hypocone, subsequently evolved. Quadrate molars have an additional fourth cusp on the lingual side called the hypocone, located posterior to the protocone. Quadrate molars appeared early in mammal evolution and are present in many species, including hedgehogs and many primates, including humans. There may be a fifth cusp. In many mammals, additional smaller cusps called, they are named after their locations, e.g. a paraconule is located between a paracone and a metacone, a hypoconulid is located between a hypoconid and an entoconid. In bunodont molars, the cusps rounded hills rather than sharp peaks, they are most common among omnivores such as pigs and humans. Bunodont molars are effective crushing devices and basically quadrate in shape.
Hypsodont dentition is characterized by high-crowned teeth and enamel that extends far past the gum line, which provides extra material for wear and tear. Some examples of animals with hypsodont dentition are cattle and horses, all animals that feed on gritty, fibrous material. Hypsodont molars can continue to grow for example in some species of Arvicolinae. Hypsodont molars lack both a neck; the occlusal surface is rough and flat, adapted for crushing and grinding plant material. The body is covered with cementum both above and below the gingival line, below, a layer of enamel covering the entire length of the body; the cementum and the enamel invaginate into the thick
The Holocene is the current geological epoch. It began 11,650 cal years before present, after the last glacial period, which concluded with the Holocene glacial retreat; the Holocene and the preceding Pleistocene together form the Quaternary period. The Holocene has been identified with the current warm period, known as MIS 1, it is considered by some to be an interglacial period within the Pleistocene Epoch. The Holocene has seen the growth and impacts of the human species worldwide, including all its written history, development of major civilizations, overall significant transition toward urban living in the present. Human impacts on modern-era Earth and its ecosystems may be considered of global significance for future evolution of living species, including synchronous lithospheric evidence, or more hydrospheric and atmospheric evidence of human impacts. In July 2018, the International Union of Geological Sciences split the Holocene epoch into three distinct subsections, Greenlandian and Meghalayan, as proposed by International Commission on Stratigraphy.
The boundary stratotype of Meghalayan is a speleothem in Mawmluh cave in India, the global auxiliary stratotype is an ice core from Mount Logan in Canada. The name Holocene comes from the Ancient Greek words ὅλος and καινός, meaning "entirely recent", it is accepted by the International Commission on Stratigraphy that the Holocene started 11,650 cal years BP. The Subcommission on Quaternary Stratigraphy quotes Gibbard and van Kolfschoten in Gradstein Ogg and Smith in stating the term'Recent' as an alternative to Holocene is invalid and should not be used and observe that the term Flandrian, derived from marine transgression sediments on the Flanders coast of Belgium has been used as a synonym for Holocene by authors who consider the last 10,000 years should have the same stage-status as previous interglacial events and thus be included in the Pleistocene; the International Commission on Stratigraphy, considers the Holocene an epoch following the Pleistocene and the last glacial period. Local names for the last glacial period include the Wisconsinan in North America, the Weichselian in Europe, the Devensian in Britain, the Llanquihue in Chile and the Otiran in New Zealand.
The Holocene can be subdivided into five time intervals, or chronozones, based on climatic fluctuations: Preboreal, Atlantic and Subatlantic. Note: "ka" means "kilo-annum" Before Present, i.e. 1,000 years before 1950 The Blytt–Sernander classification of climatic periods defined by plant remains in peat mosses, is being explored. Geologists working in different regions are studying sea levels, peat bogs and ice core samples by a variety of methods, with a view toward further verifying and refining the Blytt–Sernander sequence, they find a general correspondence across Eurasia and North America, though the method was once thought to be of no interest. The scheme was defined for Northern Europe, but the climate changes were claimed to occur more widely; the periods of the scheme include a few of the final pre-Holocene oscillations of the last glacial period and classify climates of more recent prehistory. Paleontologists have not defined any faunal stages for the Holocene. If subdivision is necessary, periods of human technological development, such as the Mesolithic and Bronze Age, are used.
However, the time periods referenced by these terms vary with the emergence of those technologies in different parts of the world. Climatically, the Holocene may be divided evenly into the Neoglacial periods. According to some scholars, a third division, the Anthropocene, has now begun; the International Commission on Stratigraphy Subcommission on Quaternary Stratigraphy’s working group on the'Anthropocene' note this term is used to denote the present time interval in which many geologically significant conditions and processes have been profoundly altered by human activities. The'Anthropocene' is not a formally defined geological unit. Continental motions due to plate tectonics are less than a kilometre over a span of only 10,000 years. However, ice melt caused world sea levels to rise about 35 m in the early part of the Holocene. In addition, many areas above about 40 degrees north latitude had been depressed by the weight of the Pleistocene glaciers and rose as much as 180 m due to post-glacial rebound over the late Pleistocene and Holocene, are still rising today.
The sea level rise and temporary land depression allowed temporary marine incursions into areas that are now far from the sea. Holocene marine fossils are known, from Vermont and Michigan. Other than higher-latitude temporary marine incursions associated with glacial depression, Holocene fossils are found in lakebed and cave deposits. Holocene marine deposits along low-latitude coastlines are rare because the rise in sea levels during the period exceeds any tectonic uplift of non-glacial origin. Post-glacial rebound in the Scandinavia region resulted in the formation of the Baltic Sea; the region continues to rise, still causing weak earthquakes across Northern Europe. The equivalent event in North America was the rebound of Hudson Bay, as it shrank from its larger, immediate post-glacial Tyrrell Sea phase, to near its present boundaries. Climate has been stable over the Holocene. Ice core
The Bactrian camel is a large, even-toed ungulate native to the steppes of Central Asia. The Bactrian camel has two humps on its back, in contrast to the single-humped dromedary camel, its population of two million exists in the domesticated form. Their name comes from the ancient historical region of Bactria. Domesticated Bactrian camels have served as pack animals in inner Asia since ancient times. With its tolerance for cold and high altitudes, it enabled the travel of caravans on the Silk Road. A small number of feral Bactrian camels still roam the Mangystau Province of southwest Kazakhstan and the Nubra Valley in India. Bactrian camels, whether domesticated or feral, are a separate species from the wild Bactrian camel, the only wild species of camel in the world; the Bactrian camel shares the genus Camelus with the wild Bactrian camel. The Bactrian camel belongs to the family Camelidae; the ancient Greek philosopher Aristotle was the first to describe the species of Camelus: in his 4th-century-BC History of Animals he identified the one-humped Arabian camel and the two-humped Bactrian camel.
The Bactrian camel was given its current binomial name Camelus bactrianus by Swedish zoologist Carl Linnaeus in his 1758 publication Systema Naturae. In 2007, Peng Cui and colleagues carried out a phylogenetic study of the evolutionary relationships between the two tribes of Camelidae: Camelini — consisting of the three Camelus species — and Lamini — consisting of the alpaca, the guanaco, the llama and the vicuña; the study revealed that the two tribes had diverged 25 million years ago, notably earlier than what had been estimated from North American fossils. Speciation began first in Lamini. Nearly two million years the Bactrian camel and the dromedary emerged as two independent species; the Bactrian camel and the dromedary interbreed to produce fertile offspring. Where the ranges of the two species overlap, such as in northern Punjab and Afghanistan, the phenotypic differences between them tend to decrease as a result of extensive crossbreeding between them; the fertility of their hybrid has given rise to speculation that the Bactrian camel and the dromedary should be merged into a single species with two varieties.
However, a 1994 analysis of the mitochondrial cytochrome b gene revealed that the species display 10.3% divergence in their sequences. The wild Bactrian camel was first described by Nikolay Przhevalsky in the late 19th century and has now been established as a distinct species from the Bactrian camel. Zoological opinion nowadays tends to favour the idea that C. bactrianus and C. dromedarius are descendants of two different subspecies of C. ferus and there is no evidence to suggest that the original range of C. ferus included those parts of Central Asia and Iran where some of the earliest Bactrian remains have been found. In particular, a population of wild Bactrian camel has been discovered to live within a part of the Gashun Gobi region of the Gobi Desert; this population is distinct from domesticated herds both in behavior. As many as three regions in the genetic makeup are distinctly different from Bactrian camels, with up to a 3% difference in the base genetic code. However, with so few wild camels, what the natural genetic diversity within a population would have been is not clear.
Another difference is the ability of these wild camels to drink saltwater slush, although whether the camel can extract useful water from it is not yet certain. Domesticated camels are unable to drink such salty water; the Bactrian camel is the largest living camel. Shoulder height is from 180 to 230 cm, head-and-body length is 225–350 cm, the tail length is 35–55 cm. At the top of the humps, the average height is 213 cm. Body mass can range from 300 to 1,000 kg, with males being much larger and heavier than females, its long, wooly coat varies in colour from dark brown to sandy beige. A mane and beard of long hair occurs with hairs measuring up to 25 cm long; the shaggy winter coat is shed rapidly, with huge sections peeling off at once, appearing as if sloppily shorn. The two humps on the back are composed of fat; the face is typical of a camelid, being somewhat triangular, with a split upper lip. The long eyelashes, along with the sealable nostrils, help to keep out dust in the frequent sandstorms which occur in their natural range.
The two broad toes on each foot have undivided soles and are able to spread as an adaptation to walking on sand. The feet are tough, as befits an animal of extreme environments; these camels are migratory, their habitat ranges from rocky mountain massifs to flat arid desert, stony plains, sand dunes. Conditions are harsh – vegetation is sparse, water sources are limited and temperatures are extreme, ranging from as low as −40 °C in winter to 40 °C in summer; the camels’ distribution is linked to the availability of water, with large groups congregating near rivers after rain or at the foot of the mountains, where water can be obtained from springs in the summer months, in the form of snow during the winter. Bactrian camels are exceptionally adept at withstanding wide variations in temperature, ranging from freezing cold to