^ Jump up to: a b Freedman, Adam H.; Gronau, Ilan; Schweizer, Rena M.; Ortega-Del Vecchyo, Diego; Han, Eunjung; Silva, Pedro M.; Galaverni, Marco; Fan, Zhenxin; Marx, Peter; Lorente-Galdos, Belen; Beale, Holly; Ramirez, Oscar; Hormozdiari, Farhad; Alkan, Can; Vilà, Carles; Squire, Kevin; Geffen, Eli; Kusak, Josip; Boyko, Adam R.; Parker, Heidi G.; Lee, Clarence; Tadigotla, Vasisht; Siepel, Adam; Bustamante, Carlos D.; Harkins, Timothy T.; Nelson, Stanley F.; Ostrander, Elaine A.; Marques-Bonet, Tomas; Wayne, Robert K.; Novembre, John (16 January 2014). "Genome Sequencing Highlights Genes Under Selection and the Dynamic Early History of Dogs". PLOS Genetics. 10 (1): e1004016. doi:10.1371/journal.pgen.1004016. PMC 3894170. PMID 24453982.
As humans became more sophisticated, so did their dogs. Eventually, there emerged specific breeds of dogs, custom-bred to suit the breeders’ local needs and circumstances. The Greyhound, for instance, was the foundation type for the immense Irish Wolfhound and the dainty Italian Greyhound. All three have a distinct family resemblance, but you’d never mistake one for another.
^ Bridgett M. von Holdt, Emily Shuldiner, Ilana Janowitz Koch, Rebecca Y. Kartzinel, Andrew Hogan, Lauren Brubaker, Shelby Wanser4, Daniel Stahler, Clive D.L. Wynne, Elaine A. Ostrander, Janet S. Sinsheimer and Monique A.R. Udell (19 July 2017). "Structural variants in genes associated with human Williams-Beuren syndrome underlie stereotypical hypersociability in domestic dogs". Science Advances. 3 (7): e1700398. Bibcode:2017SciA....3E0398V. doi:10.1126/sciadv.1700398. PMC 5517105. PMID 28776031.

The scientific evidence is mixed as to whether companionship of a dog can enhance human physical health and psychological wellbeing.[191] Studies suggesting that there are benefits to physical health and psychological wellbeing[192] have been criticised for being poorly controlled,[193] and finding that "the health of elderly people is related to their health habits and social supports but not to their ownership of, or attachment to, a companion animal." Earlier studies have shown that people who keep pet dogs or cats exhibit better mental and physical health than those who do not, making fewer visits to the doctor and being less likely to be on medication than non-guardians.[194]
In addition, people with pet dogs took considerably more physical exercise than those with cats and those without pets. The results provide evidence that keeping pets may have positive effects on human health and behaviour, and that for guardians of dogs these effects are relatively long-term.[195] Pet guardianship has also been associated with increased coronary artery disease survival, with human guardians being significantly less likely to die within one year of an acute myocardial infarction than those who did not own dogs.[196]
The practice of using dogs and other animals as a part of therapy dates back to the late 18th century, when animals were introduced into mental institutions to help socialize patients with mental disorders.[201] Animal-assisted intervention research has shown that animal-assisted therapy with a dog can increase social behaviors, such as smiling and laughing, among people with Alzheimer's disease.[202] One study demonstrated that children with ADHD and conduct disorders who participated in an education program with dogs and other animals showed increased attendance, increased knowledge and skill objectives, and decreased antisocial and violent behavior compared with those who were not in an animal-assisted program.[203]
In conformation shows, also referred to as breed shows, a judge familiar with the specific dog breed evaluates individual purebred dogs for conformity with their established breed type as described in the breed standard. As the breed standard only deals with the externally observable qualities of the dog (such as appearance, movement, and temperament), separately tested qualities (such as ability or health) are not part of the judging in conformation shows.

In the United States, cats and dogs are a factor in more than 86,000 falls each year.[183] It has been estimated around 2% of dog-related injuries treated in UK hospitals are domestic accidents. The same study found that while dog involvement in road traffic accidents was difficult to quantify, dog-associated road accidents involving injury more commonly involved two-wheeled vehicles.[184]
The scientific evidence is mixed as to whether companionship of a dog can enhance human physical health and psychological wellbeing.[191] Studies suggesting that there are benefits to physical health and psychological wellbeing[192] have been criticised for being poorly controlled,[193] and finding that "the health of elderly people is related to their health habits and social supports but not to their ownership of, or attachment to, a companion animal." Earlier studies have shown that people who keep pet dogs or cats exhibit better mental and physical health than those who do not, making fewer visits to the doctor and being less likely to be on medication than non-guardians.[194]
Where the domestication of the dog took place remains debated, with the most plausible proposals spanning Western Europe,[9][28] Central Asia[28][29] and East Asia.[28][30] This has been made more complicated by the recent proposal that an initial wolf population split into East and West Eurasian groups. These two groups, before going extinct, were domesticated independently into two distinct dog populations between 14,000 and 6,400 years ago. The Western Eurasian dog population was gradually and partially replaced by East Asian dogs introduced by humans at least 6,400 years ago.[28][2] This proposal is also debated.[2]

Dogs are highly variable in height and weight. The smallest known adult dog was a Yorkshire Terrier, that stood only 6.3 cm (2.5 in) at the shoulder, 9.5 cm (3.7 in) in length along the head-and-body, and weighed only 113 grams (4.0 oz). The largest known dog was an English Mastiff which weighed 155.6 kg (343 lb) and was 250 cm (98 in) from the snout to the tail.[31] The tallest dog is a Great Dane that stands 106.7 cm (42.0 in) at the shoulder.[32]

A 2005 paper states "recent research has failed to support earlier findings that pet ownership is associated with a reduced risk of cardiovascular disease, a reduced use of general practitioner services, or any psychological or physical benefits on health for community dwelling older people. Research has, however, pointed to significantly less absenteeism from school through sickness among children who live with pets."[191] In one study, new guardians reported a highly significant reduction in minor health problems during the first month following pet acquisition, and this effect was sustained in those with dogs through to the end of the study.[195]
Cut out mats that can't be brushed out. Severe matting can pull the skin every time the dog moves, making daily life painful for your pet. If you can't brush a mat out, you need to either cut or shave it off, depending on how close it is to the skin. Be extremely careful if you use scissors to avoid injuring yourself or your pet. Try to cut parallel to the growth of the hair to avoid a choppy look.
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