Do all dogs have dewclaws?

Not all dogs have dewclaws, as some dogs are born with dewclaws on all four legs while others have two dewclaws or even just one dewclaw. The dewclaw is not used by the dogs, but it is believed that as far back as 40 million years ago, a cat-like animal that could climb trees existed and that this is the modern dog's ancestor.

The dog's dewclaw is thought to be the remnant of this animal's fifth toe that made it possible for it climb trees much better than the other animals. The dewclaw was given its name because when dogs walk in the morning through dewy grass, this claw will touch the top of the grass with all of the dew.