The domestic dog is a domesticated canid which has been selectively bred over millennia for various behaviours, sensory capabilities, and physical attributes.
Domestication is a sustained multi-generational relationship in which one group of organisms assumes a significant degree of influence over the reproduction and care of another group to secure a more predictable supply of resources from that second group.
The domestic cat or the feral cat is a small, typically furry, carnivorous mammal.
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Although initially thought to have originated as an artificial variant of an extant canid species, extensive genetic studies undertaken during the 2010s indicate that dogs diverged from an extinct wolf-like canid in Eurasia 40,000 years ago.
Eurasia is the combined continental landmass of Europe and Asia.
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Their long association with humans has led to dogs being uniquely attuned to human behavior and are able to thrive on a starch-rich diet which would be inadequate for other canid species.
Starch or amylum is a polymeric carbohydrate consisting of a large number of glucose units joined by glycosidic bonds.
Dogs are also the oldest domesticated animal.
Dogs vary widely in shape, size and colours.
Dogs perform many roles for people, such as hunting, herding, pulling loads, protection, assisting police and military, companionship and, more recently, aiding handicapped individuals.
This influence on human society has given them the sobriquet, "man's best friend".
A sobriquet is a nickname, sometimes assumed, but often given by another.