I found a site describing sheep dogs responding to voice commands of shepherd in 1576. It is marvelous to watch border collie sheep trials, to see owner able to have dog several hundred yards away bring in a designated sheep, and drive it into fold. Border collies are very bright, but very apt to get into mischief if the do not have sheep to work on. I would not advise anyone to try to have sheep without a Border Collie to drive them into fold for the night. One dog can do what a dozen humans cannot.
If you are a dog lover, you would enjoy tear-jerking tale "The Trials of Nop".