History and evolution

Domestic dogs inherited complex behaviors from their wolf ancestors, which would have been pack hunters with complex body language. These sophisticated forms of social cognition and communication may account for their trainability, playfulness, and ability to fit into human households and social situations, and these attributes have given dogs a relationship with humans that has enabled them to become one of the most successful species on the planet today.[25] Although experts largely disagree over the details of dog domestication, it is agreed that human interaction played a significant role in shaping the subspecies.[30] Domestication may have occurred initially in separate areas, particularly Siberia and Europe. Currently it is thought domestication of our current lineage of dog occurred sometime as early as 15,000 years ago and arguably as late as 8500 years ago. Shortly after the latest domestication, dogs became ubiquitous in human populations, and spread throughout the world. Emigrants from Siberia likely crossed the Bering Strait with dogs in their company, and some experts[who?] suggest the use of sled dogs may have been critical to the success of the waves that entered North America roughly 12,000 years ago,[citation needed] although the earliest archaeological evidence of dog-like canids in North America dates from about 9,000 years ago.[31] Dogs were an important part of life for the Athabascan population in North America, and were their only domesticated animal. Dogs also carried much of the load in the migration of the Apache and Navajo tribes 1,400 years ago. Use of dogs as pack animals in these cultures often persisted after the introduction of the horse to North America.[32][page needed] The current consensus among biologists and archaeologists is that the dating of first domestication is indeterminate,[30][32] although more recent evidence shows isolated domestication events as early as 33,000 years ago.[33][34] There is conclusive evidence the present lineage of dogs genetically diverged from their wolf ancestors at least 15,000 years ago,[5][35][36] but some believe domestication to have occurred earlier.[30] Evidence is accruing that there were previous domestication events, but that those lineages died out.[7] It is not known whether humans domesticated the wolf as such to initiate dog's divergence from its ancestors, or whether dog's evolutionary path had already taken a different course prior to domestication. For example, it is hypothesized that some wolves gathered around the campsites of paleolithic camps to scavenge refuse, and associated evolutionary pressure developed that favored those who were less frightened by, and keener in approaching, humans. Tesem, an old Egyptian sighthound-like dog The bulk of the scientific evidence for the evolution of the domestic dog stems from morphological studies of archaeological findings and mitochondrial DNA studies. The divergence date of roughly 15,000 years ago is based in part on archaeological evidence that demonstrates the domestication of dogs occurred more than 15,000 years ago,[25][32] and some genetic evidence indicates the domestication of dogs from their wolf ancestors began in the late Upper Paleolithic close to the Pleistocene/Holocene boundary, between 17,000 and 14,000 years ago.[37] But there is a wide range of other, contradictory findings that make this issue controversial.[citation needed] There are findings beginning currently at 33,000 years ago distinctly placing them as domesticated dogs evidenced not only by shortening of the muzzle but widening as well as crowding of teeth. Archaeological evidence suggests that the latest point at which dogs could have diverged from wolves was roughly 15,000 years ago, although it is possible they diverged much earlier.[25] In 2008, a team of international scientists released findings from an excavation at Goyet Cave in Belgium declaring a large, toothy canine existed 31,700 years ago and ate a diet of horse, musk ox and reindeer.[38] Prior to this Belgian discovery, the earliest dog foss

ls were two large skulls from Russia and a mandible from Germany dated from roughly 14,000 years ago.[5][25] Remains of smaller dogs from Natufian cave deposits in the Middle East, including the earliest burial of a human being with a domestic dog, have been dated to around 10,000 to 12,000 years ago.[5][39] There is a great deal of archaeological evidence for dogs throughout Europe and Asia around this period and through the next two thousand years (roughly 8,000 to 10,000 years ago), with fossils uncovered in Germany, the French Alps, and Iraq, and cave paintings in Turkey.[25] The oldest remains of a domesticated dog in the Americas were found in Texas and have been dated to about 9,400 years ago.[40] DNA studies DNA studies have provided a wide range of possible divergence dates, from 15,000 to 40,000 years ago,[5] to as much as 100,000 to 140,000 years ago.[41] These results depend on a number of assumptions.[25] Genetic studies are based on comparisons of genetic diversity between species, and depend on a calibration date. Some estimates of divergence dates from DNA evidence use an estimated wolf-coyote divergence date of roughly 700,000 years ago as a calibration.[42] If this estimate is incorrect, and the actual wolf-coyote divergence is closer to one or two million years ago, or more,[43] then the DNA evidence that supports specific dog-wolf divergence dates would be interpreted very differently. Furthermore, it is believed the genetic diversity of wolves has been in decline for the last 200 years, and that the genetic diversity of dogs has been reduced by selective breeding. This could significantly bias DNA analyses to support an earlier divergence date. The genetic evidence for the domestication event occurring in East Asia is also subject to violations of assumptions. These conclusions are based on the location of maximal genetic divergence, and assume hybridization does not occur, and that breeds remain geographically localized. Although these assumptions hold for many species, there is good reason to believe that they do not hold for canines.[25] Genetic analyses indicate all dogs are likely descended from a handful of domestication events with a small number of founding females,[25][37] although there is evidence domesticated dogs interbred with local populations of wild wolves on several occasions.[5] Data suggest dogs first diverged from wolves in East Asia, and these domesticated dogs then quickly migrated throughout the world, reaching the North American continent around 8000 BC.[5] The oldest groups of dogs, which show the greatest genetic variability and are the most similar to their wolf ancestors, are primarily Asian and African breeds, including the Basenji, Lhasa Apso, and Siberian Husky.[44] Some breeds thought to be very old, such as the Pharaoh Hound, Ibizan Hound, and Norwegian Elkhound, are now known to have been created more recently.[44] A great deal of controversy surrounds the evolutionary framework for the domestication of dogs.[25] Although it is widely claimed that "man domesticated the wolf,"[45] man may not have taken such a proactive role in the process.[25] The nature of the interaction between man and wolf that led to domestication is unknown and controversial. At least three early species of the Homo genus began spreading out of Africa roughly 400,000 years ago, and thus lived for a considerable time in contact with canine species.[25] Despite this, there is no evidence of any adaptation of canine species to the presence of the close relatives of modern man. If dogs were domesticated, as believed, roughly 15,000 years ago, the event (or events) would have coincided with a large expansion in human territory and the development of agriculture. This has led some biologists to suggest one of the forces that led to the domestication of dogs was a shift in human lifestyle in the form of established human settlements. Permanent settlements would have coincided with a greater amount of disposable food and would have created a barrier between wild and anthropogenic canine populations.