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The evolution of the wolf occurred over a
The fossil record for ancient vertebrates is composed of rarely occurring fragments from which it is often impossible to obtain genetic material. Researchers are limited to morphologic analysis but it is difficult to estimate the intra-species and inter-species variations and relationships that existed between specimens across time and place. Some observations are debated by researchers who do not always agree, and hypotheses that are supported by some authors are challenged by others.
The
The evolution of the wolf occurred over a geologic time scale
The geologic time scale, or geological time scale, (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the process of relating strata to time) and geochrono ...
of at least 300 thousand years.
The grey wolf
The wolf (''Canis lupus''; : wolves), also known as the gray wolf or grey wolf, is a large canine native to Eurasia and North America. More than thirty subspecies of ''Canis lupus'' have been recognized, and gray wolves, as popularly ...
''Canis lupus'' is a highly adaptable species that is able to exist in a range of environments and which possesses a wide distribution across the Holarctic
The Holarctic realm is a biogeographic realm that comprises the majority of habitats found throughout the continents in the Northern Hemisphere. It corresponds to the floristic Boreal Kingdom. It includes both the Nearctic zoogeographical region ...
. Studies of modern grey wolves have identified distinct sub-populations that live in close proximity to each other. This variation in sub-populations is closely linked to differences in habitat – precipitation, temperature, vegetation, and prey specialization – which affect cranio-dental plasticity.
The archaeological and paleontological records show grey wolf continuous presence for at least the last 300,000 years. This continuous presence contrasts with genomic analyses, which suggest that all modern wolves and dogs descend from a common ancestral wolf population that existed as recently as 20,000 years ago. These analyses indicate a population bottleneck
A population bottleneck or genetic bottleneck is a sharp reduction in the size of a population due to environmental events such as famines, earthquakes, floods, fires, disease, and droughts; or human activities such as specicide, widespread violen ...
, followed by a rapid radiation from an ancestral population at a time during, or just after, the Last Glacial Maximum
The Last Glacial Maximum (LGM), also referred to as the Late Glacial Maximum, was the most recent time during the Last Glacial Period that ice sheets were at their greatest extent.
Ice sheets covered much of Northern North America, Northern Eur ...
. This implies that the original wolf populations were out-competed by a new type of wolf which replaced them. However, the geographic origin of this radiation is not known.
Fossil record
The fossil record for ancient vertebrates is composed of rarely occurring fragments from which it is often impossible to obtain genetic material. Researchers are limited to morphologic analysis but it is difficult to estimate the intra-species and inter-species variations and relationships that existed between specimens across time and place. Some observations are debated by researchers who do not always agree, and hypotheses that are supported by some authors are challenged by others.
The Cretaceous–Paleogene extinction event
The Cretaceous–Paleogene (K–Pg) extinction event (also known as the Cretaceous–Tertiary extinction) was a sudden mass extinction of three-quarters of the plant and animal species on Earth, approximately 66 million years ago. With the ...
occurred 65 million years ago and brought an end to the dinosaurs and the appearance of the first carnivorans. The name carnivoran is given to a member of the order Carnivora
Carnivora is a Clade, monophyletic order of Placentalia, placental mammals consisting of the most recent common ancestor of all felidae, cat-like and canidae, dog-like animals, and all descendants of that ancestor. Members of this group are f ...
. Carnivorans possess a common arrangement of teeth called carnassials
Carnassials are paired upper and lower teeth modified in such a way as to allow enlarged and often self-sharpening edges to pass by each other in a shearing manner. This adaptation is found in carnivorans, where the carnassials are the modified f ...
, in which the first lower molar and the last upper premolar
The premolars, also called premolar teeth, or bicuspids, are transitional teeth located between the canine and molar teeth. In humans, there are two premolars per quadrant in the permanent set of teeth, making eight premolars total in the mouth ...
possess blade-like enamel crowns
A crown is a traditional form of head adornment, or hat, worn by monarchs as a symbol of their power and dignity. A crown is often, by extension, a symbol of the monarch's government or items endorsed by it. The word itself is used, partic ...
that act similar to a pair of shears for cutting meat. This dental arrangement has been modified by adaptation over the past 60 million years for diets composed of meat, for crushing vegetation, or for the loss of the carnassial function altogether as in seals, sea lions, and walruses. Today, not all carnivorans are carnivores
A carnivore , or meat-eater (Latin, ''caro'', genitive ''carnis'', meaning meat or "flesh" and ''vorare'' meaning "to devour"), is an animal or plant whose food and energy requirements derive from animal tissues (mainly muscle, fat and other sof ...
, such as the insect-eating Aardwolf
The aardwolf (''Proteles cristata'') is an insectivorous species of hyena, native to East and Southern Africa. Its name means "earth-wolf" in Afrikaans and Dutch. It is also called maanhaar-jackal (Afrikaans for " mane-jackal"), termite-eatin ...
.
The carnivoran ancestors of the dog-like caniforms
Caniformia is a suborder within the order Carnivora consisting of "dog-like" carnivorans. They include dogs (wolves, foxes, etc.), bears, raccoons, and mustelids. The Pinnipedia (seals, walruses and sea lions) are also assigned to this group. ...
and the cat-like feliforms
Feliformia is a suborder within the order Carnivora consisting of "cat-like" carnivorans, including cats (large and small), hyenas, mongooses, viverrids, and related taxa. Feliformia stands in contrast to the other suborder of Carnivora, Caniform ...
began their separate evolutionary paths just after the end of the dinosaurs. The first members of the dog family Canidae
Canidae (; from Latin, ''canis'', "dog") is a biological family of dog-like carnivorans, colloquially referred to as dogs, and constitutes a clade. A member of this family is also called a canid (). There are three subfamilies found within th ...
appeared 40 million years ago, of which only its subfamily the Caninae
The Caninae, known as canines, are one of three subfamily, subfamilies found within the Canidae, canid family. The other two canid subfamilies are the extinct Borophaginae and Hesperocyoninae. The Caninae includes all living canids and their most ...
survives today in the form of the wolf-like and fox-like canines. The caniforms included the fox-like genus ''Leptocyon
The genus ''Leptocyon'' (Greek: ''leptos'' slender + ''cyon'' dog) includes 11 species and was the first canine. They were small and weighed around . They first appeared in North America around 34 million years ago in the Oligocene at the same ...
'' whose various species existed from 34 million YBP before branching 11.9 million YBP into ''Vulpes
'' Vulpes '' is a genus of the sub-family Caninae. The members of this genus are colloquially referred to as true foxes, meaning they form a proper clade. The word "fox" occurs in the common names of all species of the genus, but also appears ...
'' (foxes) and Canini (canines). The jackal-sized ''Eucyon
''Eucyon'' (Greek: : good, true; : dog) is an extinct genus of medium omnivorous coyote-like canid that first appeared in the Western United States during the late Middle Miocene 10 million years ago. It was the size of a jackal and weighed ...
'' existed in North America from 10 million YBP and by the Early Pliocene
Early may refer to:
History
* The beginning or oldest part of a defined historical period, as opposed to middle or late periods, e.g.:
** Early Christianity
** Early modern Europe
Places in the United States
* Early, Iowa
* Early, Texas
* Early ...
about 6–5 million YBP the coyote-like ''Eucyon davisi
''Eucyon'' (Greek: : good, true; : dog) is an extinct genus of medium omnivorous coyote-like canid that first appeared in the Western United States during the late Middle Miocene 10 million years ago. It was the size of a jackal and weighed ar ...
'' invaded Eurasia. In North America it gave rise to early ''Canis'' which first appeared in the Miocene
The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recen ...
(6 million YBP) in south-western US and Mexico. By 5 million YBP the larger ''Canis lepophagus
''Canis lepophagus'' (Latin: : 'dog'; : 'hare' or 'rabbit'; suffix : '-eating'; hence hare-eating dog) is an extinct species of canid which was endemic to much of North America during the Early Pliocene. It is notable because its lineage is prop ...
'' appeared in the same region.
The canids that had immigrated from North America to Eurasia – ''Eucyon
''Eucyon'' (Greek: : good, true; : dog) is an extinct genus of medium omnivorous coyote-like canid that first appeared in the Western United States during the late Middle Miocene 10 million years ago. It was the size of a jackal and weighed ...
'', ''Vulpes
'' Vulpes '' is a genus of the sub-family Caninae. The members of this genus are colloquially referred to as true foxes, meaning they form a proper clade. The word "fox" occurs in the common names of all species of the genus, but also appears ...
'', and ''Nyctereutes
''Nyctereutes'' (Greek: ''nyx, nykt-'' "night" + ''ereutēs'' "wanderer") is a genus of canid which includes only two extant species both known as raccoon dogs; the common raccoon dog (''Nyctereutes procyonoides'') and the Japanese raccoon dog (' ...
'' – were small to medium-sized predators during the Late Miocene and Early Pliocene but they were not the top predators. The position of the canids would change with the arrival of ''Canis'' to become a dominant predator across the Holarctic
The Holarctic realm is a biogeographic realm that comprises the majority of habitats found throughout the continents in the Northern Hemisphere. It corresponds to the floristic Boreal Kingdom. It includes both the Nearctic zoogeographical region ...
. The wolf-sized '' C. chihliensis'' appeared in northern China in the Mid-Pliocene around 4–3 million YBP. The large wolf-sized ''Canis'' appeared in the Middle Pliocene
The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58Pliocene
The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58Canis lepophagus
''Canis lepophagus'' (Latin: : 'dog'; : 'hare' or 'rabbit'; suffix : '-eating'; hence hare-eating dog) is an extinct species of canid which was endemic to much of North America during the Early Pliocene. It is notable because its lineage is prop ...
'' lived in the early Pliocene in North America. Björn Kurtén, Kurten proposed that the Blancan ''C. lepophagus'' derived from smaller Miocene
The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recen ...
''Canis'' species in North America. It then became widespread across Eurasia where it was either identical to, or closely related with, ''C. arnensis'' of Europe.
Johnston describes ''C. lepophagus'' as having a more slender skull and skeleton than in the modern coyote. Robert M. Nowak found that the early populations had small, delicate and narrowly proportioned skulls that resemble small coyotes and appear to be ancestral to ''Coyote, C. latrans''. Johnson noted that some specimens found in Cita Canyon, Texas, had larger, broader skulls, and along with other fragments Nowak suggested that these were evolving into wolves.
Tedford disagreed with previous authors and found that its cranio-dental morphology lacked some characteristics that are shared by ''C. lupus'' and ''C. latrans'', and therefore there was not a close relationship but it did suggest ''C. lepophagus'' was the ancestor of both wolves and coyotes.
''Canis priscolatrans''
''Canis priscolatrans'' lived in the late Pliocene-Early Pleistocene in North America. The first definite wolf appeared in the Late Blancan/Early Irvingtonian, and named ''C. priscolatrans'' that was either very close to or a synonym for ''Canis edwardii''. It resembled ''C. rufus'' in cranial size and proportions but with more complex dentition. However, there are no fossils of ''C. rufus'' until the Late Rancholabrean. Björn Kurtén, Kurtén was uncertain if ''C. priscolatrans'' derived from ''C. lepophagus'' and ''C. arnensis'', but believed that ''C. priscolatrans'' was a population of large coyotes that were ancestral to Rancholabrean and recent ''C. latrans''. He noted that ''C. arnensis'' of Europe showed striking similarities to ''C. priscolatrans'', and they could represent what once was a holarctic population of coyotes. Nowak disagreed, and believed that ''C. priscolatrans'' was a counterpart to the European ''C. etruscus''. Kurtén later proposed that both ''C. priscolatrans'' and ''C. etruscus'' were part of a group which led to ''C. lupus'' but was not sure if they evolved separately from ''C. lepophagus'' or a possible common ancestor that was derived from ''C. lepophagus''. The remains of the larger coyote-like ''Canis edwardii'' have been found in the laterPliocene
The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58
Merriam named 3 unusual species based on specimens recovered from the Rancho La Brea tar pits. They were regarded by Nowak as taxonomic synonyms for ''Canis lupus''.
''Canis occidentalis furlongi'' (Merriam 1910) was described as a wolf considerably smaller than the dire wolf and more closely related to the timber wolf ''Canis lupus occidentalis''. However, its
''Canis mosbachensis'', sometimes known as the Mosbach wolf, is an extinct small wolf that once inhabited Eurasia from the Middle Pleistocene, Middle to Late Pleistocene. The phylogenetic descent of the extant wolf ''C. lupus'' from ''C. etruscus'' through ''C. mosbachensis'' is widely accepted. In 2010, a study found that the diversity of the ''Canis'' group decreased by the end of the Early Pleistocene to Middle Pleistocene and was limited in Eurasia to the small wolves of the ''C. mosbachensis–C. variabilis'' group that were a comparable size to the extant Indian wolf (''Canis lupus pallipes''), and the large hypercarnivorous Xenocyon, ''Canis (Xenocyon) lycaonoides'' that was comparable in size to extant northern grey wolves.
premolar
The premolars, also called premolar teeth, or bicuspids, are transitional teeth located between the canine and molar teeth. In humans, there are two premolars per quadrant in the permanent set of teeth, making eight premolars total in the mouth ...
P4 (upper carnassials) were massive, and the Cusp (anatomy)#hypocone, hypocone of the Molar (tooth), molar M1 was larger than that of the dire wolf. One specimen's teeth and palate are described as being between the dire wolf and ''Canis lupus occidentalis''. Nowak proposed the name ''Canis lupus furlongi'' as he believed that it was a subspecies of the grey wolf. There is the possibility that wolves living in marginal areas led to dire wolf/grey wolf hybrids.
''Canis milleri'' (Merriam 1912), the Miller wolf, was as large as the timber wolf but with a shorter and heavier head. Its skull and dentition were described as being intermediate between ''Canis lupus occidentalis'' and the dire wolf. Its skull differed from ''occidentalis'' due to its wider skull, especially at the palate, and the size of its P4 and M1 were much larger than any known timber wolf, with the P4 approaching that of the dire wolf in size. It is regarded by Nowak as a taxonomic synonym of ''Canis lupus furlongi''.
''Aenocyon milleri'' (Merriam 1918) was described as a wolf different from the dire wolf by its smaller size, low sagittal crest, and a less prominent inion, but closer to the dire wolf than the timber wolf. Only one specimen was found. It is regarded by Nowak as a taxonomic synonym of ''Canis lupus furlongi''.
''Canis mosbachensis''
''Canis mosbachensis'', sometimes known as the Mosbach wolf, is an extinct small wolf that once inhabited Eurasia from the Middle Pleistocene, Middle to Late Pleistocene. The phylogenetic descent of the extant wolf ''C. lupus'' from ''C. etruscus'' through ''C. mosbachensis'' is widely accepted. In 2010, a study found that the diversity of the ''Canis'' group decreased by the end of the Early Pleistocene to Middle Pleistocene and was limited in Eurasia to the small wolves of the ''C. mosbachensis–C. variabilis'' group that were a comparable size to the extant Indian wolf (''Canis lupus pallipes''), and the large hypercarnivorous Xenocyon, ''Canis (Xenocyon) lycaonoides'' that was comparable in size to extant northern grey wolves.
''Canis variabilis''
In 2012, a study of the wolf-like ''Canis'' species of ancient China under the direction of Xiaoming Wang found that these were all quite close to ''C. lupus'' in both dental and post-cranial dimensions except for ''Canis mosbachensis#Canis variabilis, Canis variabilis'', which was "very strange" compared to other ''Canis'' in China as it had much smaller cranio-dental dimensions than earlier and later species. The study concluded that "It is very likely that this species is the ancestor of the domestic dog ''Canis familiaris'', a hypothesis that has been proposed by previous authors."''Canis chihliensis''
Xiaoming Wang (paleontologist), Wang and Richard H. Tedford, Tedford proposed that the genus ''Canis'' was the descendant of the coyote-like ''Eucyon
''Eucyon'' (Greek: : good, true; : dog) is an extinct genus of medium omnivorous coyote-like canid that first appeared in the Western United States during the late Middle Miocene 10 million years ago. It was the size of a jackal and weighed ...
davisi'', and its remains first appeared in the Miocene
The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recen ...
(6 million YBP) in south-western USA and Mexico. By the Pliocene
The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58Canis lepophagus
''Canis lepophagus'' (Latin: : 'dog'; : 'hare' or 'rabbit'; suffix : '-eating'; hence hare-eating dog) is an extinct species of canid which was endemic to much of North America during the Early Pliocene. It is notable because its lineage is prop ...
'' appeared in the same region and by the Early Pleistocene (1 million YBP) ''Canis latrans'' (the coyote) was in existence. They proposed that the progression from ''Eucyon davisi'' to ''C lepophagus'' to the coyote was linear evolution. Additionally, ''C. edwardii'', ''C. latrans'' and ''C. aureus'' form together a small clade and because ''C. edwardii'' appeared earliest spanning the mid-Blancan (late Pliocene) to the close of the Irvingtonian (late Pleistocene) it is proposed as the ancestor.
Nowak and Tedford also believed that it was possible for ''C. lupus'' to have been derived from a Miocene or Pliocene canid line that preceded and was separate from ''C. lepophagus''. Based on morphology from China, the Pliocene
The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58 In Italy, the earliest ''Canis lupus'' specimens were found at La Polledrara di Cecanibbio, 20 km north-west of Rome in strata dated 340,000–320,000 YBP. In 2017, a study found that the dimensions of the upper and lower carnassial teeth of the early Holocene Italian wolf are close to those of ''C. l. maximus''. Fluctuations in the size of ''C. lupus'' carnassial teeth correlate with the spread of megafauna. The Italian wolf underwent a reduction in body size with the loss of the red deer in Italy during the Renaissance. The proposed lineage is:
In 2020, a new species of wolf ''C. borjgali'' was discovered in Georgia (country), Georgia. This wolf is proposed to be the next evolutionary step after ''C. mosbachensis'' and an ancestor of the ''C. lupus'' lineage.
In 2002, a study was undertaken into the fossil skulls of two large canids that had been found buried within meters of the doorway of what was once a mammoth-bone hut at the Eliseevichi-I Upper Paleolithic site in the Bryansk Oblast, Bryansk Region on the Russian Plain, and using an accepted morphologically based definition of domestication declared them to be "Ice Age dogs". The carbon dating gave a calendar-year age estimate that ranged between 16,945–13,905 YBP. In 2013, a study looked at one of these skulls and its mitochondrial DNA sequence was identified as ''Canis familiaris''.
In 2015, a zooarchaeologist stated that "In terms of phenotypes, dogs and wolves are fundamentally different animals."
In 1986, a study of skull morphology found that the domestic dog is morphologically distinct from all other canids except the wolf-like canids. "The difference in size and proportion between some breeds are as great as those between any wild genera, but all dogs are clearly members of the same species." In 2010, a study of dog skull shape compared to extant carnivorans proposed that "The greatest shape distances between dog breeds clearly surpass the maximum divergence between species in the Carnivora. Moreover, domestic dogs occupy a range of novel shapes outside the domain of wild carnivorans."
link
/ref> "Dogs are not paedomorphic wolves." Compared to the wolf, dog dentition is relatively less robust (Olsen 1985; Hemmer 1990), which is proposed to be due to the relaxation of natural selection when wolves became commensal scavengers, or to artificial selection (Olsen 1985; Clutton-Brock 1995). However, Kieser and Groeneveld (1992) compared the mandibulo-dental measurements of jackals (''C. adustus, C. mesomelas'') and Cape foxes (''Vulpes chama'') to equivalent-sized dogs and found that the canines of these other canids tended to be slightly smaller and their second molars larger compared to dogs, otherwise the proportions were essentially the same in all species. They concluded that "...the teeth of canids appear to have evolved in concert with one another and relatively independently of differences in dimorphism, size or functional demands". This calls into question the assumption that dog teeth are relatively small due to recent selection, suggesting that dog dentition is plesiomorphic from an ancestor that was smaller than the wolf. The reduced body size of the early dog compared to a wolf is thought due to niche selection (Olsen 1985; Morey 1992; Coppinger & Coppinger 2001). Morey (1992:199) states that "Results...are consistent with a hypothesis that early domestic dogs are evolutionary paedomorphs, products of strong selection for ontogenetically channeled size reduction and alterations of reproductive timing associated with the new domestic way of life." However, in an domestication experiment the domesticated foxes remained the same size as unselected foxes (Trutt 1999:167). Wayne (1986) concluded that the dog is closer in skull morphology to ''C. latrans, C. aureus, C. adustus, C. mesomelas, Cuon alpinus'' and ''Lycaon pictus'' than to the wolf. Dahr (1942) concluded that the shape of the dog brain case is closer to that of the coyote than to that of the wolf. Manwell and Baker (1983) reviewed Dahr's work with the addition of dental data for canids and concluded that the dog ancestor was probably within the range of 13.6–20.5 kg, which is smaller than the range 27–54 kg for extant wolves (Mech 1970) and is comparable with the Dingo. The auditory Tympanic part of the temporal bone, bulla of the dog is relatively smaller and flatter than that of the wolf (Harrison 1973; Clutton-Brock, Corbet & Hill 1976; Nowak 1979; Olsen 1985; Wayne 1986), which is proposed to be due to relaxed selection under domestication as the dog no longer required the acute hearing of the wolf. However, bulla shape has been shown to facilitate increased sensitivity to specific frequencies but shape and size may not be correlated with acuity (Ewer 1973). Therefore, the observed difference could be that the dog bulla has retained its ancestral shape. The ventral edge of the dog's horizontal ramus of the mandible has a convex curve that does not exist in the wolf (Olsen 1985; Clutton-Brock 1995), and no discussion of this difference could be found in the literature. However, Biknevicius and Van Valkenburgh (1997) noticed that the horizontal ramus of bone-processing predators is thicker dorso-ventrally at the point Anatomical terms of location#caudal, caudal to the site of bone processing. This thickening may have been a function for niche adaptation by the dog's ancestor. A description of the superficial brain morphology of jackals (''C. mesomelas, C. aureus''), coyotes (''C. latrans''), wolves (''C. lupus, C. rufus''), and dogs indicated that the cerebellum of the dog closely approximates that of the coyote, which is closely aligned with the jackals, and that the wolves show numerous brain traits distinct from the other species (Atkins and Dillon 1971). Wolves also have serological and biochemical traits distinct from dogs (Leone and Wiens 1956; Lauer, Kuyt & Baker 1969). The tails of domestic dogs tend to curl upwards, which is not found in other canid. Dogs possess a domed forehead, which is easy to see in a profile view with a bulge above the Orbit (anatomy), orbit (the bony socket) of the eye. The temporalis muscle that closes the jaws is more robust in wolves. Compared with equally sized wolves, dogs possess 20% smaller skulls, and compared with equally weighted wolves dogs possess 20% smaller brains. The Auditory bulla, tympanic bullae are large, convex, and almost spherical in wolves, while the bullae of dogs are smaller, compressed, and slightly crumpled. Dogs have a distinctive "stop" between the forehead and nose. Domestic dogs are distinguishable from wolves by starch gel electrophoresis of red blood cell acid phosphatase. During the Last Glacial Maximum, there was greater wolf genetic diversity than there is today, and within the Pleistocene grey wolf population the variations between local environments would have encouraged a range of wolf ecotypes that were genetically, morphologically and ecologically distinct from one another. One author has proposed that the most likely explanation for the different morphological characteristics of the dog compared to the wolf is that the dog's ancestor was adapted to a different niche than the wolf.
In 2018, whole genome sequencing was used to compare members of genus ''Canis'', along with the dhole (''Cuon alpinus'') and the African hunting dog (''Lycaon pictus''). There is evidence of gene flow between African golden wolves, golden jackals, and grey wolves. The study suggests that the African golden wolf is a descendant of a genetically genetic admixture, admixed canid of 72% grey wolf and 28% Ethiopian wolf ancestry, and that the Ethiopian wolf once had a wider range in Africa. One African golden wolf from the Egyptian Sinai Peninsula showed high admixture with the Middle Eastern grey wolves and dogs, highlighting the role of the land bridge between the African and Eurasian continents in canid evolution. There is evidence of gene flow between golden jackals and Middle Eastern wolves, less so with European and Asian wolves, and least with North American wolves. The study proposes that the golden jackal ancestry found in North American wolves may have occurred before the divergence of the Eurasian and North American grey wolves. The study indicates that the common ancestor of the coyote and grey wolf has genetically Genetic admixture, admixed with a ghost population of an extinct unidentified canid. The canid is genetically close to the dhole and has evolved after the divergence of the African hunting dog from the other canid species. The Basal (phylogenetics), basal position of the coyote compared to the wolf is proposed to be due to the coyote retaining more of the mitochondrial genome of this unknown canid.
A genomic study on the wolves of China included museum specimens of wolves from southern China that were collected between 1963 and 1988. The wolves in the study formed 3 clades: north Asian wolves that included those from northern China and eastern Russia, Himalayan wolf, Himalayan wolves from the Tibetan Plateau, and a unique population from southern China. One specimen located as far southeast as Jiangxi province shows evidence of being admixed between Tibetan-related wolves and other wolves in China. One specimen from Zhejiang province in eastern China shared gene flow with the wolves from southern China, however its genome was 12-14 percent admixed with a canid that may be the dhole or an unknown canid that predates the genetic divergence of the dhole. The wolf population from southern China is believed to be still existing in that region.
In 2016, a study built on the work of another major study and analyzed the sequences of 12 genes that are located on the heavy strand of the mitochondrial genome of extinct and modern ''C. lupus''. The study excluded the sequences of the divergent Himalayan wolf and the Indian wolf#Canis indica, Indian grey wolf. The ancient specimens were radiocarbon dated and Stratigraphy, stratagraphically dated, and together with the sequences generated a time-based phylogenetic tree. From the tree, the study was able to infer the most recent common ancestor for all other ''C. lupus'' specimens – modern and extinct – was 80,000 YBP and this date concurred with the earlier study. The study could find no evidence of a population bottleneck for wolves until a few thousand years ago.
The phylogenetic tree showed the polyphyly of American wolves, the Mexican wolf was divergent from other North American wolves, and these other North American wolves formed two closely related clades. A scenario consistent with the phylogenetic, ice sheet and sea-level data was that during the Ice Age when sea levels were at their lowest, there was a single wave of wolf colonization into North America starting with the opening of the Bering land bridge 70,000 YBP and closing during the Late Glacial Maximum of the Yukon corridor that ran through the division between the Laurentide Ice Sheet and the Cordilleran Ice Sheet 23,000 YBP. Mexican wolves were part of the single wave and either diverged from the other wolves before entering North America or once in North America due to the change in its environment.
As wolves had been in the fossil record of North America but modern wolves could trace their ancestry back only 80,000 years, the wolf haplotypes that were already in North America were replaced by these invaders, either through competitive displacement or through admixture. The replacement in North America of a basal population of wolves by a more recent one supported the findings of earlier studies. There possibly existed a panmictic wolf population with gene flow spanning Eurasia and North America until the closing of the ice sheets. Once the sheets closed, the southern wolves were isolated and north of the sheets only the Beringian wolf existed. The land bridge became inundated by the sea 10,000 YBP, the sheets receded 12,000–6,000 YBP, the Beringian wolf went extinct and the southern wolves expanded to recolonize the rest of North America. All North American wolves are descended from those that were once isolated south of the ice sheets. However, much of their diversity was later lost during the twentieth century.
Studies using mitochondrial DNA have indicated that the wolves of coastal south-east Alaska are genetically distinct from inland grey wolves, reflecting a pattern also observed in other taxa. They show a phylogenetic relationship with extirpated wolves from the south (Oklahoma), indicating that these wolves are the last remains of a once widespread group that has been largely extirpated during the last century, and that the wolves of northern North America had originally expanded from southern refuges below the Wisconsin glaciation after the ice had melted at the end of the
''Canis c.f. familiaris'' - Paleolithic dog
There are a number of recently discovered specimens which are proposed as being Paleolithic dogs, however their taxonomy is debated. These have been found in either Europe or Siberia and date 40,000-17,000 YBP. They include Hohle Fels in Germany, Goyet Caves in Belgium, Předmostí u Přerova (archeology), Predmosti in the Czech Republic, and four sites in Russia: Razboinichya Cave, Kostyonki (palaeolithic site), Kostyonki-8, Ulakhan Sular, and Eliseevichi 1. Paw-prints from Chauvet Cave in France dated 26,000 YBP are suggested as being those of a dog, however these have been challenged as being left by a wolf. Paleolithic dogs were directly associated with human hunting camps in Europe over 30,000 (YBP) and it is proposed that they were domesticated. They are also proposed to be either a proto-dog and the ancestor of the domestic dog or a type of wolf unknown to science.''Canis familiaris'' (domestic dog)
In 2002, a study was undertaken into the fossil skulls of two large canids that had been found buried within meters of the doorway of what was once a mammoth-bone hut at the Eliseevichi-I Upper Paleolithic site in the Bryansk Oblast, Bryansk Region on the Russian Plain, and using an accepted morphologically based definition of domestication declared them to be "Ice Age dogs". The carbon dating gave a calendar-year age estimate that ranged between 16,945–13,905 YBP. In 2013, a study looked at one of these skulls and its mitochondrial DNA sequence was identified as ''Canis familiaris''.
In 2015, a zooarchaeologist stated that "In terms of phenotypes, dogs and wolves are fundamentally different animals."
In 1986, a study of skull morphology found that the domestic dog is morphologically distinct from all other canids except the wolf-like canids. "The difference in size and proportion between some breeds are as great as those between any wild genera, but all dogs are clearly members of the same species." In 2010, a study of dog skull shape compared to extant carnivorans proposed that "The greatest shape distances between dog breeds clearly surpass the maximum divergence between species in the Carnivora. Moreover, domestic dogs occupy a range of novel shapes outside the domain of wild carnivorans."
Comparison with modern wolves
The domestic dog compared to the modern wolf shows the greatest variation in the size and shape of the skull (Evans 1979) that range from 7 to 28 cm in length (McGreevy 2004). Wolves are dolichocephaly, dolichocephalic (long skulled) but not as extreme as some breeds of such as greyhounds and Russian wolfhounds (McGreevy 2004). Canine brachycephaly (short-skulledness) is found only in domestic dogs and is related to paedomorphosis (Goodwin 1997). Puppies are born with short snouts, with the longer skull of dolichocephalic dogs emerging in later development (Coppinger 1995). Other differences in head shape between brachycephalic and dolichocephalic dogs include changes in the craniofacial angle (angle between the Basilar plexus, basilar axis and hard palate) (Regodón 1993), morphology of the temporomandibular joint (Dickie 2001), and radiographic anatomy of the cribriform plate (Schwarz 2000). Nowak indicated that orbital angle of the eye socket is an important characteristic defining the difference between the dog and the wolf, with the wolf having the lower angle. Nowak compared the orbital angles of four North American Canis, canines (including the Indian dog) and produced the following values in degrees: coyote-42.8, wolf-42.8, dog-52.9 dire wolf-53.1. The orbital angle of the eye socket was clearly larger in the dog than in the coyote and the wolf; why it was almost the same as that of the dire wolf was not commented on. Many authors have concluded that compared to the adult extant wolf, the adult domestic dog has a relatively reduced rostrum (front part of the skull), an elevated frontal bone, a wider palate, a broader cranium, and smaller teeth (Hildebrand1954; Clutton-Brock, Corbet & Hills 1976; Olsen 1985; Wayne 1986; Hemmer 1990; Morey 1990). Other authors have disagreed and have stated that these traits can overlap and vary within the two (Crockford 1999; Harrison 1973). Wolf cubs have similar relative skull proportions as adult dogs and this was proposed as evidence that the domestic dog is a Neoteny, neotenic wolf. This was proposed to be due to either human selection for juvenile appearance or due to a Pleiotropy, pleiotropic effect as a result of selection for juvenile behavior (Clutton-Brock 1977; Belyaev 1979; Wayne 1986; Coppinger and Schneider 1995). Wayne (1986) concluded that his dog samples did not have significant relative shortening of the rostrum compared to wolves, calling this identification feature into question. A 2004 study that used 310 wolf skulls and over 700 dog skulls representing 100 breeds concluded that the evolution of dog skulls can generally not be described by heterochronic processes such as neoteny although some pedomorphic dog breeds have skulls that resemble the skulls of juvenile wolves.Drake, Abby Grace, "Evolution and development of the skull morphology of canids: An investigation of morphological integration and heterochrony" (January 1, 2004). Doctoral Dissertations Available from Proquest. Paper AAI3136721link
/ref> "Dogs are not paedomorphic wolves." Compared to the wolf, dog dentition is relatively less robust (Olsen 1985; Hemmer 1990), which is proposed to be due to the relaxation of natural selection when wolves became commensal scavengers, or to artificial selection (Olsen 1985; Clutton-Brock 1995). However, Kieser and Groeneveld (1992) compared the mandibulo-dental measurements of jackals (''C. adustus, C. mesomelas'') and Cape foxes (''Vulpes chama'') to equivalent-sized dogs and found that the canines of these other canids tended to be slightly smaller and their second molars larger compared to dogs, otherwise the proportions were essentially the same in all species. They concluded that "...the teeth of canids appear to have evolved in concert with one another and relatively independently of differences in dimorphism, size or functional demands". This calls into question the assumption that dog teeth are relatively small due to recent selection, suggesting that dog dentition is plesiomorphic from an ancestor that was smaller than the wolf. The reduced body size of the early dog compared to a wolf is thought due to niche selection (Olsen 1985; Morey 1992; Coppinger & Coppinger 2001). Morey (1992:199) states that "Results...are consistent with a hypothesis that early domestic dogs are evolutionary paedomorphs, products of strong selection for ontogenetically channeled size reduction and alterations of reproductive timing associated with the new domestic way of life." However, in an domestication experiment the domesticated foxes remained the same size as unselected foxes (Trutt 1999:167). Wayne (1986) concluded that the dog is closer in skull morphology to ''C. latrans, C. aureus, C. adustus, C. mesomelas, Cuon alpinus'' and ''Lycaon pictus'' than to the wolf. Dahr (1942) concluded that the shape of the dog brain case is closer to that of the coyote than to that of the wolf. Manwell and Baker (1983) reviewed Dahr's work with the addition of dental data for canids and concluded that the dog ancestor was probably within the range of 13.6–20.5 kg, which is smaller than the range 27–54 kg for extant wolves (Mech 1970) and is comparable with the Dingo. The auditory Tympanic part of the temporal bone, bulla of the dog is relatively smaller and flatter than that of the wolf (Harrison 1973; Clutton-Brock, Corbet & Hill 1976; Nowak 1979; Olsen 1985; Wayne 1986), which is proposed to be due to relaxed selection under domestication as the dog no longer required the acute hearing of the wolf. However, bulla shape has been shown to facilitate increased sensitivity to specific frequencies but shape and size may not be correlated with acuity (Ewer 1973). Therefore, the observed difference could be that the dog bulla has retained its ancestral shape. The ventral edge of the dog's horizontal ramus of the mandible has a convex curve that does not exist in the wolf (Olsen 1985; Clutton-Brock 1995), and no discussion of this difference could be found in the literature. However, Biknevicius and Van Valkenburgh (1997) noticed that the horizontal ramus of bone-processing predators is thicker dorso-ventrally at the point Anatomical terms of location#caudal, caudal to the site of bone processing. This thickening may have been a function for niche adaptation by the dog's ancestor. A description of the superficial brain morphology of jackals (''C. mesomelas, C. aureus''), coyotes (''C. latrans''), wolves (''C. lupus, C. rufus''), and dogs indicated that the cerebellum of the dog closely approximates that of the coyote, which is closely aligned with the jackals, and that the wolves show numerous brain traits distinct from the other species (Atkins and Dillon 1971). Wolves also have serological and biochemical traits distinct from dogs (Leone and Wiens 1956; Lauer, Kuyt & Baker 1969). The tails of domestic dogs tend to curl upwards, which is not found in other canid. Dogs possess a domed forehead, which is easy to see in a profile view with a bulge above the Orbit (anatomy), orbit (the bony socket) of the eye. The temporalis muscle that closes the jaws is more robust in wolves. Compared with equally sized wolves, dogs possess 20% smaller skulls, and compared with equally weighted wolves dogs possess 20% smaller brains. The Auditory bulla, tympanic bullae are large, convex, and almost spherical in wolves, while the bullae of dogs are smaller, compressed, and slightly crumpled. Dogs have a distinctive "stop" between the forehead and nose. Domestic dogs are distinguishable from wolves by starch gel electrophoresis of red blood cell acid phosphatase. During the Last Glacial Maximum, there was greater wolf genetic diversity than there is today, and within the Pleistocene grey wolf population the variations between local environments would have encouraged a range of wolf ecotypes that were genetically, morphologically and ecologically distinct from one another. One author has proposed that the most likely explanation for the different morphological characteristics of the dog compared to the wolf is that the dog's ancestor was adapted to a different niche than the wolf.
Genetic record
DNA sequences
The mitochondria within each Cell (biology), cell contain many copies of a small circular DNA genome and in mammals it is 16,000–18,000 base pairs in length. A cell contains hundreds or thousands of mitochondria and therefore the genes contained within those mitochondria are more abundant than the genes that occur in the nucleus of the cell. The abundance of mitochondrial DNA (mDNA) is useful for the genetic analysis of ancient remains where the DNA has degraded. Mitochondrial DNA sequences have a higher mutation rate than the mutation rate of nuclear genes and for mammals this rate is 5–10 times faster. The mitochondrial protein-coding genes evolve much faster and are powerful markers for inferring evolution history at category levels such as families, genera, and species. However, they have evolved at a faster rate than other DNA markers and there is a timing difference in its molecular clock that needs to be validated against other sources. The taxonomic status of uncertain species is better resolved through using nuclear DNA from the nucleus of the cell, which is more suitable for analyzing the recent history. In most cases, mDNA is inherited from the maternal ancestor. Therefore, phylogenetic analysis of mDNA sequences within species provides a history of maternal lineages that can be represented as a phylogenetic tree.
The mutations that are different in these 4 Sequence alignment, sequences have been numbered and bolded. These mutations can then be used to build a phylogenetic tree for the four canids. In this example, the dog and grey wolf differ by two substitutions (highlighted in red), and each of them differs from the coyote by four substitutions.
The mDNA sequences of the dog and wolf differ by only 0–12 substitutions within 261 base-pairs, whereas dogs always differed from coyotes and jackals by at least 20 substitutions. This finding implies that the dog derived from the wolf and that there has been repeated back-crossing, or that the dog may have descended from a now extinct species of canid whose closest living relative is the modern wolf.
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Golden JackalA-G-C-T-G-T-C-GA-T-TC-CA
Coyote A-G-C-T-A-T-C-GA-A-TC-GA
Wolf T-G-C-T-A-T-G-GA-T-TC-CT
Dog T-G-G-T-A-T-G-GA-T-TC-CA
Marker issue
Different DNA studies may give conflicting results because of the specimens selected, the technology used, and the assumptions made by the researchers. Any one from a panel of genetic markers can be chosen for use in a study. The techniques used to DNA extraction, extract, DNA sequencing, locate and DNA analysis, compare genetic sequences can be applied using advances in technology, which allows researchers to observe longer lengths of Base pair#Length measurements, base pairs that provide more data to give better phylogenetic resolution. Phylogenetic trees compiled using different genetic markers have given conflicting results on the relationship between the wolf, dog and coyote. One study based on Single-nucleotide polymorphism, SNPs (a single mutation), and another based on nuclear gene sequences (taken from the cell nucleus), showed dogs clustering with coyotes and separate from wolves. Another study based on SNPS showed wolves clustering with coyotes and separate from dogs. Other studies based on a number of markers show the more widely accepted result of wolves clustering with dogs separate from coyotes. These results demonstrate that caution is needed when interpreting the results provided by genetic markers.Timing issue
There are two key assumptions that are made for dating the divergence time for species: the generation time and the genetic mutation rate per generation. The time between generations for wolves is assumed to be three years based on the extant grey wolf, and two years for the dog based on the extant dog. One recent major study assumed a generation time of 2 years for the dog for as far back as 10,000 years ago, and then assumed a generation time of 3 years (the same as the wolf) before that to calculate a proposed divergence time between the two. In 2017, the wolf research scientist L. David Mech queried why evolutionary biologists were calculating the approximate time of the dog diverging from the wolf through using a wolf generation time of three years when published works using large data sets demonstrate a figure of 4.2–4.7 years. They were encouraged to recalculate their divergence dates accordingly. DNA studies are conducted but with "the mutation rate as the dominant source of uncertainty." In 2005, Lindblad-Toh sequenced the first draft genome of the extant dog, and calculated a proposed mutation rate of 1x10−8 mutations per generation. In 2015, Skoglund was able to sequence the first draft genome of the 35,000 YBP Pleistocene wolf#Taimyr wolf, Taimyr wolf and used its radio-carbon date to validate a proposed genetic mutation rate of 0.4x10−8 mutations per generation. The difference is a timing factor of 2.5, however another study stated that because only one Pleistocene wolf specimen has so far been sequenced, then the result should be treated with caution, with that study then providing both estimates to calculate the proposed divergence times between the wolf and dog. However, in 2016 the mutation rate of the 4,800 YBP Origin of the domestic dog#Late Pleistocene wolf admixture, Newgrange dog matched that of the Taimyr wolf.Wolf-like canids
The wolf-like canids (the canid subfamilyCaninae
The Caninae, known as canines, are one of three subfamily, subfamilies found within the Canidae, canid family. The other two canid subfamilies are the extinct Borophaginae and Hesperocyoninae. The Caninae includes all living canids and their most ...
) are a group of large carnivores that are genetically closely related because their chromosomes number 78. The group includes genus ''Canis'', ''Cuon'' and ''Lycaon''. The members are the dog ''(C. familiaris)'', grey wolf (''C. lupus''), coyote (''C. latrans''), golden jackal (''C. aureus''), Ethiopian wolf (''C. simensis''), black-backed jackal (''Lupulella mesomelas''), side-striped jackal (''Lupulella adusta''), dhole (''Cuon alpinus''), and African wild dog (''Lycaon pictus''). Newly proposed members include the red wolf (''Canis rufus''), eastern wolf (''Canis lycaon''), and African golden wolf (''C. anthus''). As they possess 78 chromosomes, all members of the genus ''Canis'' (coyotes, wolves, jackals) are Karyology, karyologically indistinguishable from each other, and from the dhole and the African hunting dog. The members of ''Canis'' can potentially hybrid (biology), interbreed and there is evidence that the Ethiopian wolf has hybridized with dogs. According to zoologist Reginald Innes Pocock, Reginald Pocock, a dhole interbred with a golden jackal. The African hunting dog is large, highly mobile, known to disperse over large distances and are rare throughout much of their geographical range, making opportunities for hybridization difficult. A study of the maternal mitochondrial DNA of the black-backed jackal could find no evidence of genotypes from the most likely mates – the side-striped jackal nor the golden jackal – indicating that male black-backed jackals had not bred with these. A search of the scientific literature could not find evidence of hybridization for the rare side-striped jackal.
A DNA sequence alignment for the wolf-like canids gave a phylogenetic tree with the grey wolf and dog being the most closely related, followed by a close affiliation with the coyote, golden jackal and Ethiopian wolf, and the dog can hybridize in the wild with these three species. Next closest to this group are the dhole and African wild dog that both have unique meat-slicing teeth, suggesting that this adaptation was later lost by the other members. The two African jackals are shown as the most Basal (phylogenetics), basal members of this clade, which means that this tree is indicating an African origin for the clade. The tree illustrates the genotype–phenotype distinction, where a genotype is an organism's full hereditary information and a phenotype is an organism's actual observed properties, such as morphology (biology), morphology, Developmental biology, development, or behavior. By phenotype, the dhole (genus ''Cuon'') and the African hunting dog (genus ''Lycaon'') are not classified as members of the genus ''Canis'', but by genotype they are closer to dogs, wolves and coyotes than are the two genus ''Canis'' jackals – the Side-striped jackal (''C. adustus'') and the Black-backed jackal (''C. mesomelas'').
In 2015, a study of mitochondrial genome sequences and nuclear genome sequences of African and Eurasian canids indicated that extant wolf-like canids had colonized Africa from Eurasia at least 5 times throughout the Pliocene and Pleistocene, which is consistent with fossil evidence suggesting that much of the African canid diversity resulted from the immigration of Eurasian ancestors, likely coincident with Plio-Pleistocene climatic oscillations between arid and humid conditions.
The phylogenetic tree for the wolf-like canids may give conflicting positions for the black-backed jackal and the side-striped jackal relative to the genus ''Canis'' members depending on whether the genetic markers were based on mitochondrial DNA or nuclear DNA. The explanation proposed for this mito-nuclear discord is that mitochondrial DNA introgression occurred from an ancient ancestor of genus ''Canis'' into the lineage that led to the black-backed jackal around 6.2–5.2 million years ago.
Phylogenetic tree of the extant wolf-like canids, with the pink shading representing the species ''Canis lupus''.
Admixture with an extinct unknown canid
In 2018, whole genome sequencing was used to compare members of genus ''Canis'', along with the dhole (''Cuon alpinus'') and the African hunting dog (''Lycaon pictus''). There is evidence of gene flow between African golden wolves, golden jackals, and grey wolves. The study suggests that the African golden wolf is a descendant of a genetically genetic admixture, admixed canid of 72% grey wolf and 28% Ethiopian wolf ancestry, and that the Ethiopian wolf once had a wider range in Africa. One African golden wolf from the Egyptian Sinai Peninsula showed high admixture with the Middle Eastern grey wolves and dogs, highlighting the role of the land bridge between the African and Eurasian continents in canid evolution. There is evidence of gene flow between golden jackals and Middle Eastern wolves, less so with European and Asian wolves, and least with North American wolves. The study proposes that the golden jackal ancestry found in North American wolves may have occurred before the divergence of the Eurasian and North American grey wolves. The study indicates that the common ancestor of the coyote and grey wolf has genetically Genetic admixture, admixed with a ghost population of an extinct unidentified canid. The canid is genetically close to the dhole and has evolved after the divergence of the African hunting dog from the other canid species. The Basal (phylogenetics), basal position of the coyote compared to the wolf is proposed to be due to the coyote retaining more of the mitochondrial genome of this unknown canid.
A genomic study on the wolves of China included museum specimens of wolves from southern China that were collected between 1963 and 1988. The wolves in the study formed 3 clades: north Asian wolves that included those from northern China and eastern Russia, Himalayan wolf, Himalayan wolves from the Tibetan Plateau, and a unique population from southern China. One specimen located as far southeast as Jiangxi province shows evidence of being admixed between Tibetan-related wolves and other wolves in China. One specimen from Zhejiang province in eastern China shared gene flow with the wolves from southern China, however its genome was 12-14 percent admixed with a canid that may be the dhole or an unknown canid that predates the genetic divergence of the dhole. The wolf population from southern China is believed to be still existing in that region.
Out of Beringia
Grey wolves suffered a species-widepopulation bottleneck
A population bottleneck or genetic bottleneck is a sharp reduction in the size of a population due to environmental events such as famines, earthquakes, floods, fires, disease, and droughts; or human activities such as specicide, widespread violen ...
(reduction) approximately 25,000 YBP during the Last Glacial Maximum. This was followed by a single population of modern wolves expanding out of a Beringia#Beringian refugium, Beringia refuge to repopulate the wolf's former range, replacing the remaining Late Pleistocene wolf populations across Eurasia and North America as they did so. This source population probably did not give rise to dogs, but admixed with dogs which allowed them to gain coat colour genes that are also related to immunity, and provided dogs with genes which allowed them to adapt to high-altitude environments (e.g. Tibet). This suggests that the genetic divergence of European and East Asian dogs could be based on admixture with different sub-populations of wolves.
There is little genetic information available on the ancient wolves that existed prior to the bottleneck. However, studies show that one or more of these ancient populations is more directly ancestral to dogs than are modern wolves, and conceivably these were more prone to domestication by the first humans to invade Eurasia.
As of 2020, the oldest known intact wolf remains belongs to a mummified pup dated 56,000 YBP that was recovered from the permafrost along a small tributary of Last Chance Creek near Dawson City, Yukon, Canada. A DNA analysis showed that it belonged to the Beringian wolf clade, that the most recent common ancestor of this clade dates to 86,700–67,500 YBP, and that this clade was basal to all other wolves except for the Himalayan wolf.
Into America and Japan
In 2016, a study built on the work of another major study and analyzed the sequences of 12 genes that are located on the heavy strand of the mitochondrial genome of extinct and modern ''C. lupus''. The study excluded the sequences of the divergent Himalayan wolf and the Indian wolf#Canis indica, Indian grey wolf. The ancient specimens were radiocarbon dated and Stratigraphy, stratagraphically dated, and together with the sequences generated a time-based phylogenetic tree. From the tree, the study was able to infer the most recent common ancestor for all other ''C. lupus'' specimens – modern and extinct – was 80,000 YBP and this date concurred with the earlier study. The study could find no evidence of a population bottleneck for wolves until a few thousand years ago.
The phylogenetic tree showed the polyphyly of American wolves, the Mexican wolf was divergent from other North American wolves, and these other North American wolves formed two closely related clades. A scenario consistent with the phylogenetic, ice sheet and sea-level data was that during the Ice Age when sea levels were at their lowest, there was a single wave of wolf colonization into North America starting with the opening of the Bering land bridge 70,000 YBP and closing during the Late Glacial Maximum of the Yukon corridor that ran through the division between the Laurentide Ice Sheet and the Cordilleran Ice Sheet 23,000 YBP. Mexican wolves were part of the single wave and either diverged from the other wolves before entering North America or once in North America due to the change in its environment.
As wolves had been in the fossil record of North America but modern wolves could trace their ancestry back only 80,000 years, the wolf haplotypes that were already in North America were replaced by these invaders, either through competitive displacement or through admixture. The replacement in North America of a basal population of wolves by a more recent one supported the findings of earlier studies. There possibly existed a panmictic wolf population with gene flow spanning Eurasia and North America until the closing of the ice sheets. Once the sheets closed, the southern wolves were isolated and north of the sheets only the Beringian wolf existed. The land bridge became inundated by the sea 10,000 YBP, the sheets receded 12,000–6,000 YBP, the Beringian wolf went extinct and the southern wolves expanded to recolonize the rest of North America. All North American wolves are descended from those that were once isolated south of the ice sheets. However, much of their diversity was later lost during the twentieth century.
Studies using mitochondrial DNA have indicated that the wolves of coastal south-east Alaska are genetically distinct from inland grey wolves, reflecting a pattern also observed in other taxa. They show a phylogenetic relationship with extirpated wolves from the south (Oklahoma), indicating that these wolves are the last remains of a once widespread group that has been largely extirpated during the last century, and that the wolves of northern North America had originally expanded from southern refuges below the Wisconsin glaciation after the ice had melted at the end of the Last Glacial Maximum
The Last Glacial Maximum (LGM), also referred to as the Late Glacial Maximum, was the most recent time during the Last Glacial Period that ice sheets were at their greatest extent.
Ice sheets covered much of Northern North America, Northern Eur ...
. A Whole genome sequencing, whole-genome DNA study indicated that all North American wolves were monophyletic and therefore are the descendants of a common ancestor.
During the same period, the Soya Strait between Hokkaido and Sakhalin Island was dry for 75,000 years and it was proposed that the extinct Ezo Wolf, Ezo wolf (''C. l. hattai'') arrived on Hokkaido from Sakhalin. However, the sequences indicated that it arrived in Hokkaido less than 10,000 YBP. The Ezo wolf was closely related to one of the North American clades, but different from the more southerly Japanese wolf (''C. l. hodophilax'') that was basal to modern wolves. The Japanese wolf inhabited Kyushu, Shikoku, and Honshu islands but not Hokkaido Island. This indicates that its ancestor may have migrated from the Asian continent through the Korean Peninsula into Japan. The past sea levels of the Korean Strait together with the timing of the Japanese wolf sequences indicated that it arrived to the southern islands less than 20,000 YBP. In 2020, a genomic study found that the Japanese wolf was the last of the Siberian Pleistocene wolves, which were thought to have gone extinct at the end of the Late Pleistocene (11,700 years ago). Some of these had survived into the 20th Century and had admixed with Japanese dogs.
The dog was a very successful invader of North America and had established a widespread ecological niche by the Early–Middle Holocene. There was no overlap in niche between the dog and the wolf in comparison to the dog and other North American canids. By the Late Holocene, the dog's niche area was less in size than researchers had expected to find, indicating that it was limited by Biotic component, biotic factors. These regions include the northeast and northwest of the United States that correlate with the greatest densities of early human occupation, indicating that the dog had "defected" from the wolf niche to the human niche and explains why the dog's niche area was not as large as expected. The separation between dog and wolf may reflect the rapid rate in which domestication occurred, including the possibility of a second domestication event occurring in North America. Packs of wolves and hunter-gatherers hunt similar prey in a similar way within a similar group social structure that may have facilitated wolf domestication.
The wolf was exterminated in the southern part of their historic geographical range in North America by the middle of the 20th century. An mDNA study of 34 wolf remains from North America dated between 1856 and 1915 found their genetic diversity to be twice that of modern wolves in these regions, and two thirds of the haplotypes identified were unique. These results indicate that a historic population of several hundred thousand wolves once existed in Mexico and the western US.
Divergence with the coyote
In 1993, a study proposed that the wolves of North America display skull traits more similar towards the coyote than those wolves from Eurasia. In 2016, a Whole genome sequencing, whole-genome DNA study proposed, based on the assumptions made, that all of the North American wolves and coyotes diverged from a common ancestor less than 6,000–117,000 years ago. The study also indicated that all North American wolves have a significant amount of coyote ancestry and all coyotes some degree of wolf ancestry, and that the red wolf and eastern wolf are highly Genetic admixture, admixed with different proportions of grey wolf and coyote ancestry. However, the test that was used cannot differentiate between anceint and recent hybridization. One test indicated a wolf/coyote divergence time of 51,000 years before present that matched other studies indicating that the extant wolf came into being around this time. Another test indicated that the red wolf diverged from the coyote between 55,000–117,000 years before present and the Great Lakes region wolf 32,000 years before present. But a 2000 study on the haplotypes of North American canids showed that the divergences between coyotes, grey wolves, red wolves, and algonquin (eastern) wolves happened much earlier. This study showed that there was a 3.2 % divergence between the eastern Canadian wolf and coyote gene sequences, and a 2.3 % sequence divergence between the red wolf and coyote haplotypes. However, the divergence was a much greater 8.0% between gray wolf (C. lupus) mtDNA and eastern/red wolf haplotypes, and 10.0% between gray wolf and coyote haplotypes. The sequence difference observed between eastern Canadian wolf sequences and coyote sequences is consistent with a separation of 150 000 – 300 000 years, using a divergence rate of 1–2% per 100 000 years. Additionally, conflicting with the recent divergent hypothesis, the fossil record that indicates a coyote-like specimen dated to 1 million years before present. The modern grey wolf expanded out of Beringia 25,000 years ago. The modern coyote appeared around 10,000 years ago, and most likely descended from the Pleistocene coyote. The most genetically basal coyote mDNA clade pre-dates theLast Glacial Maximum
The Last Glacial Maximum (LGM), also referred to as the Late Glacial Maximum, was the most recent time during the Last Glacial Period that ice sheets were at their greatest extent.
Ice sheets covered much of Northern North America, Northern Eur ...
and is a haplotype that can only be found in the Eastern wolf. This implies that the large, wolf-like Pleistocene coyote was the ancestor of the Eastern wolf and Red wolf, which diverged from each other later in time.
Domestic dog
The domestic dog (''Canis lupus familiaris'') is the most widely abundant large carnivore. Over the past million years, numerous wolf-like forms existed but their turnover has been high, and modern wolves are not the lineal ancestors of dogs. Although research had suggested that dogs and wolves were genetically very close relatives, later phylogenetic analysis strongly supported the hypothesis that dogs and wolves are reciprocally monophyly, monophylic taxa that form two sister clades. This suggests that none of the modern wolf populations are related to the wolves that were first domesticated and the wolf ancestor of dogs is therefore presumed extinct. Recent mitochondrial DNA analyses of ancient and modern grey wolf specimens supports a pattern of population reduction and turnover. An alternate proposal is that during the ecological upheavals of the Late Pleistocene all of the remaining members of a dwindling lineage joined humans. In 2016, a study investigated for the first time the population subdivisions, demography, and the relationships of grey wolves based on their Whole genome sequencing, whole-genome sequences. The study indicated that the dog was a divergent subspecies of the grey wolf and was derived from a now-extinct ghost population of Late Pleistocene wolves, and the dog and the dingo are not separate species. The genome-wide phylogenetic tree indicated a genetic divergence between New World and Old World wolves, which was then followed by a divergence between the dog and Old World wolves 27,000YBP – 29,000 YBP. The dog forms a sister taxon with Eurasian grey wolves but not North American wolves. The dog had considerable pre-ancestry after its divergence from the Old World wolves before it separated into distinct lineages that are nearly as distinct from one another as they are from wolves. The study suggested that previous datings based on the divergence between wolves and coyotes of one million years ago using fossils of what appeared to be coyote-like specimens may not reflect the ancestry of the modern forms. The study indicated that the Mexican wolf was also a divergent form of grey wolf, suggesting that may have been part of an early invasion into North America. The Tibetan wolf was found to be the most highly divergent of the Old World wolves, had suffered a historical population bottleneck and had only recently recolonized the Tibetan Plateau. Glaciation may have caused its habitat loss, genetic isolation then local adaption. The study indicated that there has been extensive genetic admixture between domestic dogs and wolves, with up to 25% of the genome of Old World wolves showing signs of dog ancestry, possibly as the result of gene flow from dogs into wolves that were ancestral to all modern wolves. There was evidence of significant gene flow between the European wolves plus the Israeli wolf with the basenji and Boxer (Dog), boxer, which suggests admixture between the lineages ancestral to these breeds and wolf populations. For the lowland Asian wolves: the Central Russian and East Russian wolves and all of the lowland Chinese wolves had significant gene flow with the Chinese indigenous dogs, the Tibetan Mastiff and the dingo. For the highland Asian wolves: The Tibetan wolves did not show significant admixture with dogs; however, the Qinghai wolves had gene flow with the dingo and one of them had gene flow with the Chinese dogs. The New World wolves did not show any gene flow with the boxer, dingo or Chinese indigenous dogs but there was indication of gene flow between the Mexican wolf and the African basenji. All species within the genus ''Canis'', the Canidae#Phylogenetic relationships, wolf-like canids, are phylogenetically closely related with 78 chromosomes and can potentially hybrid (biology), interbreed. There was indication of gene flow into the golden jackal from the population ancestral to all wolves and dogs (11.3%–13.6%) and much lower rates (up to 2.8%) from extant wolf populations. The data indicated that all wolves shared similar population trajectories, followed by population decline that coincided with the expansion of modern humans worldwide and their technology for capturing large game. Late Pleistocene carnivores would have been social living in large prides, clans and packs in order to hunt the larger game available at that time, and these larger groups would have been more conspicuous targets for human persecutors. Large dogs accompanying the humans may have accelerated the rate of decline of carnivores that competed for game, therefore humans expanded across Eurasia, encountered wolves, domesticated some and possibly caused the decline of others. The study concluded that admixture had confounded the ability to make inferences about the place of dog domestication. Past studies based on SNPs, genome-wide similarities with Chinese wolves, and lower linkage disequilibrium might reflect regional admixture between dogs with wolves and gene flow between dog populations, with divergent dog breeds possibly maintaining more wolf ancestry in their genome. The study proposed that analysis of ancient DNA might be a better approach. In the same year, a study found that there were only 11 fixed genes that showed variation between wolves and dogs. These genes are thought to affect tameness and emotional processing ability. Another study provided a listing of all of the grey wolf and dog mDNA haplotypes combined in the one phylogenetic tree. In 2018, a study compared the sequences of 61,000 Single-nucleotide polymorphisms (mutations) taken from across the genome of grey wolves. The study indicated that there exists individual wolves of dog/wolf ancestry in most of the wolf populations of Eurasia but less so in North America. The hybridization has been occurring across different time scales and was not a recent event. Low-level hybridization did not reduce the wolf distinctiveness.Dingo
The dingo (''Canis familiaris dingo'') refers to the dog found in Australia. The dingo is a divergent subspecies of the grey wolf and is not a separate species, and is considered genetically to be a Basal (phylogenetics), basal member of the domestic dog clade. The genetic evidence indicates that the dingo originated from East Asian domestic dogs and was introduced through the South-East Asian archipelago into Australia, with a common ancestry between the Australian dingo and the New Guinea Singing Dog.