Dog

Dogs are widely regarded as the first species domesticated by humans and the only large carnivore ever domesticated. Genetic and archaeological evidence places their origin within a broad window, with most estimates for when dogs diverged from wolf populations falling somewhere between about 20,000 and 40,000 years ago, and some of the earliest widely accepted dog remains dated to around 17,500 years ago.

Unlike livestock species such as cattle, sheep, and goats, which were not domesticated until roughly 11,000 years ago alongside the rise of agriculture, dogs formed a relationship with humans during the Pleistocene, while people were still hunter-gatherers. This long, separate history means dogs underwent thousands of years of association with humans before the more recent selective breeding that produced today's distinct breeds.

Centuries of selective breeding have produced a very large number of distinct dog breeds, with more than 400 recognized somewhere in the world today. Major kennel clubs recognize different subsets of these: the American Kennel Club (AKC) in the United States fully recognizes 202 breeds as of 2025, while the Federation Cynologique Internationale (FCI), which coordinates breed recognition across many countries, recognizes 356 breeds organized into ten groups by appearance or working role.

Breed standards typically define not just appearance but also temperament and working ability, reflecting the wide range of original purposes dogs were bred for, from herding and guarding livestock to hunting, retrieving, and companionship. This breeding history is a major reason adult size and lifespan vary so much from one breed to another.