As dogs became tamed and domesticated by humans over many thousands of years, the canine species underwent an evolution into hundreds of breeds designed to perform particular, specific tasks, such as pulling sleds and guarding sheep. Over time, there was a decreased need for many breeds. For example, as humans evolved from hunter-gatherers into farmers, it was no longer at all necessary for them to own hunting dogs. Later, as farming societies became industrialized, there was a disappearance of herd animals, and fewer shepherds watching sheep meant that there were fewer sheepdogs. But by this time humans had grown accustomed to dogs’ companionship, and breeding continued. Today, most dogs are kept by their owners simply as companions, but some dogs still do the work they were intentionally bred for, such as following a scent, guarding a home, or leading the blind.