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In 2002, a study proposed that immediate human ancestors and wolves may have domesticated each other through a strategic alliance that would change both respectively into humans and dogs. The effects of human psychology, hunting practices, territoriality and social behavior would have been profound.[120]

Early humans moved from scavenging and small-game hunting to big-game hunting by living in larger, socially more-complex groups, learning to hunt in packs, and developing powers of cooperation and negotiation in complex situations. As these are characteristics of wo

Early humans moved from scavenging and small-game hunting to big-game hunting by living in larger, socially more-complex groups, learning to hunt in packs, and developing powers of cooperation and negotiation in complex situations. As these are characteristics of wolves, dogs and humans, it can be argued that these behaviors were enhanced once wolves and humans began to cohabit. Communal hunting led to communal defense. Wolves actively patrol and defend their scent-marked territory, and perhaps humans had their sense of territoriality enhanced by living with wolves.[120] One of the keys to recent human survival has been the forming of partnerships. Strong bonds exist between same-sex wolves, dogs and humans and these bonds are stronger than exist between other same-sex animal pairs. Today, the most widespread form of inter-species bonding occurs between humans and dogs. The concept of friendship has ancient origins but it may have been enhanced through the inter-species relationship to give a survival advantage.[120][121]

In 2003, a study compared the behavior and ethics of chimpanzees, wolves and humans. Cooperation among humans' closest genetic relative is limited to occasional hunting episodes or the persecution of a competitor for personal advantage, which had to be tempered if humans were to become domesticated.[64][122] The closest approximation to human morality that can be found in nature is that of the grey wolf, Canis lupus. Wolves are among the most gregarious and cooperative of animals on the planet,[64][65] and their ability to cooperate in well-coordinated drives to hunt prey, carry items too heavy for an individual, provisioning not only their own young but also the other pack members, babysitting etc. are rivaled only by that of human societies. Similar forms of cooperation are observed in two closely related canids, the African wild dog and the Asian dhole, therefore it is reasonable to assume that canid sociality and cooperation are old traits that in terms of evolution predate human sociality and cooperation. Today's wolves may even be less social than their ancestors, as they have lost access to big herds of ungulates and now tend more toward a lifestyle similar to coyotes, jackals, and even foxes.[64] Social sharing within families may be a trait that early humans learned from wolves,[64][123] and with wolves digging dens long before humans constructed huts it is not clear who domesticated whom.[124][64][122]

On the mammoth steppe the wolf's ability to hunt in packs, to share risk fairly among pack members, and to cooperate moved them to the top of the food chain above lions, hyenas and bears. Some wolves followed the great reindeer herds, eliminating the unfit, the weaklings, the sick and the aged, and therefore improved the herd. These wolves had become the first pastoralists hundreds of thousands of years before humans also took to this role.[124] The wolves' advantage over their competitors was that they were able to keep pace with the herds, move fast and enduringly, and make the most efficient use of their kill by their ability to "wolf down" a large part of their quarry before other predators had detected the kill. The study proposed that during the Last Glacial Maximum, some of our ancestors teamed up with those pastoralist wolves and learned their techniques.[64][125]

Many of our ancestors remained gatherers and scavengers, or specialized as fish-hunters, hunter-gatherers, and hunter-gardeners. However, some ancestors adopted the pastoralist wolves' lifestyle as herd followers and herders of reindeer, horses, and other hoofed animals. They harvested the best stock for themselves while the wolves kept the herd strong, and this group of humans was to become the first herders and this group of wolves was to become the first dogs.[124][64]

First dogs

The dog was the first species and the only large carnivore to have been domestica

Many of our ancestors remained gatherers and scavengers, or specialized as fish-hunters, hunter-gatherers, and hunter-gardeners. However, some ancestors adopted the pastoralist wolves' lifestyle as herd followers and herders of reindeer, horses, and other hoofed animals. They harvested the best stock for themselves while the wolves kept the herd strong, and this group of humans was to become the first herders and this group of wolves was to become the first dogs.[124][64]

The dog was the first species and the only large carnivore to have been domesticated. Over the past 200 years, dogs have undergone rapid phenotypic change and were formed into today's modern dog breeds due to artificial selection imposed by humans. These breeds can vary in size and weight from a 0.46 kg (1.0 lb) teacup poodle to a 90 kg (200 lb) giant mastiff. The skull, body, and limb proportions vary significantly between breeds, with dogs displaying more phenotypic diversity than can be found within the entire order of carnivores. Some breeds demonstrate outstanding skills in herding, retrieving, scent detection, and guarding, which demonstrates the functional and behavioral diversity of dogs. There have been major advances in understanding the genes that gave rise to the phenotypic traits of dogs. The first dogs were certainly wolflike; however, the phenotypic changes that coincided with the dog–wolf genetic divergence are not known.[3]

Bonn-Oberkasse

In 1914, on the eve of the First World War, two human skeletons were discovered during basalt quarrying at Oberkassel, Bonn in Germany. With them were found a right mandible of a "wolf" and other animal bones.[126] After the end of the First World War, in 1919 a full study was made of these remains. The mandible was recorded as "Canis lupus, the wolf" and some of the other animal bones were assigned to it.[127] The remains were then stored and forgotten for fifty years. In the late 1970s there was renewed interest in the Oberkassel remains and the mandible was re-examined and reclassified as belonging to a domesticated dog.[128][129][130] The mitochondrial DNA sequence of the mandible was matched to Canis lupus familiaris – dog,[35] and confirms that the Oberkassel dog is a direct ancestor of today's dogs.[131] The bodies were dated to 14,223 YBP.[132] This implies that in Western Europe there were morphologically and genetically "modern" dogs in existence around 14,500 YBP.[133]

Later studies assigned more of the other animal bones to the dog until most of a skeleton could be assembled.[133] The humans were a man aged 40 years and a woman aged 25 years. All three skeletal remains were found covered with large 20 cm thick basalt blocks and were sprayed with red hematite powder.[132] The consensus is that a dog was buried along with two humans.[133] A tooth belonging to a smaller and older dog was also identified but it had not been sprayed with red powder.[132] The cause of the d

Later studies assigned more of the other animal bones to the dog until most of a skeleton could be assembled.[133] The humans were a man aged 40 years and a woman aged 25 years. All three skeletal remains were found covered with large 20 cm thick basalt blocks and were sprayed with red hematite powder.[132] The consensus is that a dog was buried along with two humans.[133] A tooth belonging to a smaller and older dog was also identified but it had not been sprayed with red powder.[132] The cause of the death of the two humans is not known.[133] A pathology study of the dog remains suggests that it had died young after suffering from canine distemper between ages 19 and 23 weeks.[132] The dog could not have survived during this period without intensive human care.[133][132] During this period the dog was of no utilitarian use to humans,[132] and suggests the existence of emotional or symbolic ties between these humans and this dog.[133] In conclusion, near the end of the Late Pleistocene at least some humans regarded dogs not just materialistically, but had developed emotional and caring bonds for their dogs.[132]

In 2020, the sequencing of ancient dog genomes indicates that dogs share a common ancestry and descended from an ancient, now-extinct wolf population - or closely related wolf populations - which was distinct from the modern wolf lineage. Since domestication, there was almost negligible gene flow from wolves into dogs but substantial gene flow from dogs into wolves across Eurasia. There were some wolves that were related to all ancient and modern dogs. There was no gene flow detected from the Tibetan wolf into Tibetan dogs. A very small amount of gene flow was detected between coyotes and ancient American dogs, and between the African golden wolf and African dogs. By the close of the Ice Age (11,700 YBP), five ancestral lineages had diversified from each other, and were expressed in dog samples taken from the Neolithic era Levant, Mesolithic era Karelia, Mesolithic era Baikal, ancient America, and the New Guinea singing dog.[134]

The world's dog population structure follows a divide along an east-west axis. The western side includes ancient and modern dogs from western Eurasia and modern dogs from Africa. The eastern side includes ancient dogs from pre-European contact America and Baikal in Siberia, and modern East Asian dogs which includes the dingo and New Guinea singing dog that represent unadmixed East Asian ancestry.[134]

Ancient and modern European dogs have a closer relationship with eastern dogs than do Near Eastern dogs, indicating a major admixture event in Europe. The earliest Mesolithic Karelian dog dated 10,900 YBP was partially derived from an eastern dog lineage and partially from a Levantine lineage. The earliest Neolithic European dog dated 7,000 YBP was found to be a mixture of the Karelian and the Levantine lineages. The lineage of a Neolithic dog dated 5,000 YBP found in southwestern Sweden was the ancestor of 90-100% of modern European dogs. This implies that in Europe a population of half-Karelian and half-Levantine dogs similar to this one - but not necessarily originating in Sweden - replaced all of the other dog populations. These findings together support a dual ancestry for modern European dogs, which possess 54% Karelian and 46% Levantine ancestries.[134]

Ancient dog genomes were compared with ancient human genomes across time, space, and cultural context to reveal that these generally matched each other. These generally share similar features but they differ across time. There were some large differences: the same dogs could be found in both the Neolithic Levant and later in Chalcolithic Iran although the human populations of each were different; in Neolithic Ireland and Germany the dogs are more associated with northern European hunter-gatherers while the humans were more associated with people from the Levant; and on the Bronze Age Pontic–Caspian steppe and in Corded Ware culture Germany the human population had shifted away from the Neolithic European populations but the dogs had not. European dogs have a stronger genetic relationship to Siberian and ancient American dogs than to the New Guinea singing dog, which has an East Asian origin, reflecting an early polar relationship between humans in the Americas and Europe. People living in the Lake Baikal region 18,000—24,000 YBP were genetically related to western Eurasians and contributed to the ancestry of Native Americans, however these were then replaced by other populations. Ten thousand years later, around 7,000 YBP, the dogs in the Lake Baikal region still exhibited a relationship with Europe and the Americas. This implies that there was a shared population structure for both dogs and humans across circumpolar northern Eurasia.[134]

During the Upper Paleolithic (50,000–10,000 YBP), the increase in human population density, advances in blade and hunting technology, and climate change may have altered prey densities and made scavenging crucial to the survival of some wolf populations. Adaptations to scavenging such as tameness, small body size, and a decreased age of reproduction would reduce their hunting efficiency further, eventually leading to obligated scavenging.[31][135] Whether these earliest dogs were simply human-commensal scavengers or they played some role as companions or hunters that hastened their spread is unknown.[31]

Researchers have proposed that in the past a hunting partnership existed between humans and dogs that was the basis for dog domestication.[136][137][138] Petroglyph rock art dating to 8,000 YBP at the sites of Shuwaymis and Jubbah, in northwestern Saudi Arabia, depict large numbers of dogs participating in hunting scenes with some being controlled on leashes.[139] The transition from the Late Pleistocene into the early Researchers have proposed that in the past a hunting partnership existed between humans and dogs that was the basis for dog domestication.[136][137][138] Petroglyph rock art dating to 8,000 YBP at the sites of Shuwaymis and Jubbah, in northwestern Saudi Arabia, depict large numbers of dogs participating in hunting scenes with some being controlled on leashes.[139] The transition from the Late Pleistocene into the early Holocene was marked by climatic change from cold and dry to warmer, wetter conditions and rapid shifts in flora and fauna, with much of the open habitat of large herbivores being replaced by forests.[138] In the early Holocene, it is proposed that along with changes in arrow-head technology that hunting dogs were used by hunters to track and retrieve wounded game in thick forests.[137][138] The dog's ability to chase, track, sniff out and hold prey can significantly increase the success of hunters in forests, where human senses and location skills are not as sharp as in more open habitats. Dogs are still used for hunting in forests today.[138]

The domestic dog was present 9,500 YBP on what is now Zhokhov Island, arctic northeastern Siberia. The archaeological discoveries at the Zhokhov site includes the remains of dog harness straps similar to those used by the modern Inuit, the bone remains of polar bears and reindeer which suggests a wide hunting range and the transport of large body parts back to the site, and tools made from obsidian transported from 1,500 kilometres away. These findings suggest long-distance transport through the use of sled dogs.[140]

A study of dog remains indicates that these were selectively bred to be either as sled dogs or as hunting dogs, which implies that a sled dog standard and a hunting dog standard existed at that time. The optimal maximum size for a sled dog is 20–25 kg based on thermo-regulation, and the ancient sled dogs were between 16–25 kg. The same standard has been found in the remains of sled dogs from this region 2,000 YBP and in the modern Siberian husky breed standard. Other dogs were more massive at 30 kg and appear to be dogs that had been crossed with wolves and used for polar bear hunting. At death, the heads of the dogs had been carefully separated from their bodies by humans, probably for ceremonial reasons.[141]

The study proposes that after having diverged from the common ancestor shared with the grey wolf, the evolution of the dog proceeded in three stages. The first was natural selection based on feeding behavior within the ecological niche that had been formed through human activity. The second was artificial selection based on tamability. The third was directed selection based on forming breeds that possessed qualities to help with specific tasks within the human economy. The process commenced 30,000–40,000 YBP with its speed increasing in each stage until domestication became complete.Siberian husky breed standard. Other dogs were more massive at 30 kg and appear to be dogs that had been crossed with wolves and used for polar bear hunting. At death, the heads of the dogs had been carefully separated from their bodies by humans, probably for ceremonial reasons.[141]