The dog or domestic dog (Canis familiaris or Canis lupus familiaris) is a domesticated descendant of the
wolf,
and is characterized by an upturning tail. The dog is derived from an ancient, extinct wolf, and the modern
wolf
is the dog's nearest living relative. The dog was the first species to be domesticated, by hunter–gatherers
over 15,000 years ago, before the development of agriculture. Due to their long association with humans,
dogs have
expanded to a large number of domestic individuals and gained the ability to thrive on a starch-rich
diet that would
be inadequate for other canids.
The dog has been selectively bred over millennia for various behaviors, sensory capabilities, and physical
attributes. Dog breeds vary widely in shape, size, and color. They perform many roles for humans, such as
hunting,
herding, pulling loads, protection, assisting police and the military, companionship, therapy, and aiding
disabled
people. Over the millennia, dogs became uniquely adapted to human behavior, and the human-canine bond has
been a topic
of frequent study. This influence on human society has given them the sobriquet of "man's best friend".
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