SHEEP. If the dog is humankind's best friend, then sheep are its most ancient provider. Sheep may be the first domesticated ruminant, tamed by nomadic people in the Middle East and Asia 11,000 years ago, perhaps even before agriculture gave rise to civilization. Thousands of years before sheep appear in the writings of Abrahamic faiths, they were slaughtered for religious rituals. Neolithic farmers, who raised them for meat, herded them into Europe. Wool breeds appeared at least 8,000 years ago, in plenty of time to supply the looms of ancient Egypt and Babylon. Vikings carried sheep to Iceland. The Spanish brought them to the Americas. Today, sheep are found from the Arctic region to Australia and in the tropics from Africa to the Caribbean. Yet the world's billion sheep are a modest source of meat. Humans eat ten times as much pork as lamb and mutton. Sheep is not a forbidden food, though. It is eaten readily by Hindus, Muslims,...