The dog or domestic dog (Canis familiaris) is a domesticated descendant of the
grey wolf. It has many notable
characteristics, the most prominent of which is the upturning tail. The
dog derived from an ancient, extinct wolf. Today, the modern grey wolf
is the dog's nearest living relative. The dog was the first species to
be domesticated; it is believed that domestication took place over
15,000 years ago and was performed by hunter–gatherers 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. Over the
millennia, dogs became uniquely adapted to human behavior, and the
human-canine bond has been a topic of frequent study.