|Subspecies||C. l. familiaris (Domesticated dog)|
Dogs are one of the most well-known domesticated species, with archaeological and historical records showing that they have lived in a mutually beneficial relationship with humans for thousands of years.
Offspring are called pups (or puppies) until around a year old. The collective noun for a group of offspring is a litter.
Research has shown that it is probable that the first settlers of the Americas brought dogs of some sort with them. The case in Australia is not so clear. The dingo was not found in Tasmania, evidence that it was introduced to Australia after Tasmania became an island after the last Ice Age. It was introduced to Australia either in a subsequent wave of immigration or by Asian visitors.
Dogs (scientific name Canis lupus familiaris) are a subspecies of wolves, divided into a multitude of different breeds all in principle capable of interbreeding (though in some cases, physical relations between representatives of two breeds are unlikely or problematic - Chihuahuas and Great Danes, for example).
Fossils of canine skulls smaller than those of wolves have been found with human artifacts, with dates based on evolutionary assumptions estimated to between 130,000 and 190,000 years ago. whilst DNA evidence has been used to suggest that dogs diverged from wolves between 100,000 and 135,000 years ago.  Secular archeology has placed the earliest known domestication at potentially 12,000 BC-10,000 BC and with certainty at 7,000 BC. 
Dogs are also viewed as being the single most genetically diverse species on Earth - largely thanks to human-imposed selective breeding, the vast array of dog breeds surpasses any other creature on the planet. Due to selective breeding by man, however, many breeds of dog have significant genetic disorders. These include hip dysplasia (particularly common in German Shepherds, although common in most big breeds), and respiratory problems caused by shortening of the face, as seen with Boxer dogs and the Bulldog's lip and Pugs smashed faces with wrinkles that collect dirt that must be washed out regularly or may become infected. To overcome the prevalence of genetic disorders rendered common by inbreeding, many breeders regularly practice outcrossing, or introducing new material into a breed line via mating with other kinds of dog. This restores vigor to a breed and can decrease the likelihood of genetic disorders manifesting.
Despite being colloquially known as "man's best friend", every 40 seconds, someone in the United States seeks medical help for a dog bite, with approximately 800,000 such bites per year requiring medical attention. Due to the high cost of dog bite liability claims, some insurance companies have blacklisted certain breeds and refuse to provide homeowners insurance to those who own these dog breeds.  American Pit Bull Terriers are commonly thought of as one such dog, as they account for a small percent of the population, but over half of fatal attacks, although the majority of them are sweet and gentle, but all have powerful jaw muscles (they were bred for the cruel sport of dog fighting). Rottweilers are also strong and considered dangerous due to a disproportionately high number of attacks, but can also (like most dogs with nice responsible owners) be nice and friendly.
Dogs are used for many purposes:
- Being a companion for the old or lonely (or for anyone)
- Guarding property and livestock
- Herding sheep and cattle
- Tracking by scent, carrying messages, and mountain and water rescue
- Pursuing, flushing and retrieving game, and killing vermin
- Providing assistance to people with disabilities
- Military and police duties including guarding, tracking, interrogation, and attacking. In World War II, the Soviet Union attempted to train dogs to place explosive charges under German tanks, which commonly resulted in the dogs returning to their handlers just as the bombs went off.
- For certain jobs in the military that involve things humans are not able to do, such as smelling bombs crawling or through tight spaces easily
- To detect cadavers, explosives, or illegal drugs
- For fire/search and rescue missions (German Shepherds and Labrador Retrievers, among others, were used at the World Trade Center to help find survivors buried in the rubble)
- To protect people and their homes from burglars/break ins
(German Shepherds, Belgian Malinois Shepherds, Doberman Pinschers and other dogs are popular for these roles due to their intelligence, trainability, strength, loyalty, and intimidating size, appearance, and bark which can deter criminals and can potentially take them down or subdue them without causing serious harm e.g. shooting them)
- As a beast of burden, or for drawing sledges, sleighs, and dogcarts (Siberian Huskies and Alaskan Malamutes are used for these jobs a lot, due to their strength, speed, energy, endurance, intelligence, ability to work in a group, and their ability to live (and be comfortable) in extremely cold temperatures)
- As a performing animal. Circus dogs have been trained to dance, ride bicycles, speak, and walk the tightrope (this is not necessarily cruel, as long as they are treated well and not forced to do things their bodies are not designed to do)
- For fighting, which as cruel and is now illegal in most places, e.g. everywhere in USA and most of the civilized world (Pit bulls were bred for this, which is why their jaws are so strong)
- As food. Dog is still considered a delicacy in China, Korea and parts of Africa today (although many people in those places are now beginning to see it as uncivilized)
Today most dogs in western countries are kept for companionship only. Stray and feral dogs cause many problems, spreading diseases such as rabies, and attacking people and livestock. Muslims see dogs as unclean, and often kill dogs found as pets .
- Kingsley, Danny, Humans live a dog's life
- Vila, Carles; Carles Vila, Peter Savolainen, Jesus E. Maldonado, Isabel R. Amorim, John E. Rice, Rodney L. Honeycutt, Keith A. Crandall, Joakim Lundeberg, Wayne, Robert F. (1997-01-30; accepted 1997-04-14). Multiple and ancient origins of the domestic dog, Science 276: 1687-1689. Retrieved on 2006-12-09.
- Scott, John Paul (1965), Dog behavior: The genetic basis, University of Chicago Press. ISBN 0-226-74338-1.