The genetic divergence between dogs and wolves occurred between 40,000–20,000 years ago, just before or during the Last Glacial Maximum. This timespan represents the upper time-limit for the commencement of domestication because it is the time of divergence and not the time of domestication, which occurred later. The domestication of animals commenced over 15,000 years ago, beginning with the grey wolf (Canis lupus) by nomadic hunter-gatherers. The archaeological record and genetic analysis show the remains of the Bonn–Oberkassel dog buried beside humans 14,200 years ago to be the first undisputed dog, with disputed remains occurring 36,000 years ago. It was not until 11,000 years ago that people living in the Near East entered into relationships with wild populations of aurochs, boar, sheep, and goats.
In the United States, cats and dogs are a factor in more than 86,000 falls each year. 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.
Decide if you need to clip your dog's coat. Many breeds have short hair and don't require regular clipping. However, if you have a shaggier breed of dog, he may require regular clipping as part of his health routine. Breeds that need regular coat trims include cocker spaniel, sheepdog, poodle, collie, Shih Tzu, Pekingese, and chow chow, among others.
Clip the dog's nails. If left untrimmed, a dog's nails can curl under into the paw pads or twist toes in a way that causes joint damage. To keep your dog's nails short, clip them regularly, depending on how fast his nails grow. If you can hear his nails on the ground when he walks, that means his nails are touching the ground, and are too long. 
Domestic dogs have been selectively bred for millennia for various behaviors, sensory capabilities, and physical attributes. Modern dog breeds show more variation in size, appearance, and behavior than any other domestic animal. Dogs are predators and scavengers, and like many other predatory mammals, the dog has powerful muscles, fused wrist bones, a cardiovascular system that supports both sprinting and endurance, and teeth for catching and tearing.
In domestic dogs, sexual maturity happens around six to twelve months of age for both males and females, although this can be delayed until up to two years old for some large breeds. This is the time at which female dogs will have their first estrous cycle. They will experience subsequent estrous cycles semiannually, during which the body prepares for pregnancy. At the peak of the cycle, females will come into estrus, being mentally and physically receptive to copulation. Because the ova survive and are capable of being fertilized for a week after ovulation, it is possible for more than one male to sire the same litter.
^ Wood, Lisa; Martin, Karen; Christian, Hayley; Nathan, Andrea; Lauritsen, Claire; Houghton, Steve; Kawachi, Ichiro; McCune, Sandra (2015). "The Pet Factor – Companion Animals as a Conduit for Getting to Know People, Friendship Formation and Social Support". PLoS ONE. 10 (4): e0122085. Bibcode:2015PLoSO..1022085W. doi:10.1371/journal.pone.0122085. PMC 4414420. PMID 25924013.
Dogs bear their litters roughly 58 to 68 days after fertilization, with an average of 63 days, although the length of gestation can vary. An average litter consists of about six puppies, though this number may vary widely based on the breed of dog. In general, toy dogs produce from one to four puppies in each litter, while much larger breeds may average as many as twelve.
Where the domestication of the dog took place remains debated, with the most plausible proposals spanning Western Europe, Central Asia and East Asia. 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. This proposal is also debated.
We continually review and update our pet grooming policies, procedures and standards, under the supervision of our Director of Veterinary Medicine, with counsel from a number of independent experts in animal care, behavior and ethics. We continue to train our teams on and reinforce the critical importance of following those policies at all times. Since 2015, we've worked together with the Pet Industry Joint Advisory Council (PIJAC) and the Professional Pet Groomers & Stylists Alliance (PPGSA) to encourage and support national health and safety standards for the grooming industry. We believe these standards are critical to the wellbeing of pets everywhere, and we continue to work with other pet industry leaders to encourage industry-wide adoption and adherence to them.