Dogs are thought to have been the first animals domesticated by humans, perhaps 11,000 years ago. They were valuable as hunting companions because they could flush out, attack, and retrieve game. With the development of tools and weapons much earlier, humans had largely ceased being prey. With the help of dogs, they became much more successful hunters. Dogs were also valuable as beasts of burden, guards against predators and enemies, and as dependable companions. In some cultures, or in an emergency, they were a source of food.