They have accompanied humans for at least 20,000 years and possibly as many as 40,000.
Scientists generally agree that all dogs, domestic and wild,
share a common wolf ancestor; at some point grey wolves and dogs went on their separate evolutionary ways.
Today humans have bred hundreds of different domestic dog breeds—some of which could never survive in the wild.
Despite their many shapes and sizes all domestic dogs,
from Newfoundlands to pugs, are members of the same species—Canis familiaris.
Although they have domestic temperaments, dogs are related to wolves, foxes, and jackals.
Similarities to Wild Relatives
Domestic dogs still share many behaviors with their wild relatives.
Both defend their territories and mark them by urinating on trees, rocks, fence posts, and other suitable sites.
These scent posts serve notice to other dogs that an animal is occupying its territory.
Many pet dogs also bury bones or favorite toys for future use,
just as their wild relatives sometimes bury a kill to secure the meat for later feasts.