History of Chickens
Long ago, lots of wild chickens lived in India and East Asia (China, Thailand, and Vietnam). That's where people first domesticated (tamed) chickens, maybe around 7000 BC. Recent genetic evidence shows that people tamed chickens in two different places: in China and in India. Probably the people in each place didn't know that the other ones were also taming chickens. By about 5000 BC, people in China were certainly keeping chickens, and by 3000 BC people in India also had domesticated chickens.
People ate the chickens and they also ate their eggs. Chickens were easy to keep, and small enough to eat in one meal, so you didn't have to worry about the meat going bad. And you could eat their eggs as well. Both the meat and the eggs are good sources of protein.
Cockfighting in Thailand
Chickens slowly spread from India to West Asia, but they remained exotic specialty items. In West Asia and Egypt, the main reason for keeping chickens may have been not for food but for the popular sport of cock-fighting. You take two roosters and put them in a cage or pit together and they will fight over the territory. People place bets on which rooster will win. Often the loser dies in the fight.
Rooster (Corinthian plate, ca. 550 BC)
In West Asia, chickens weren't commonly kept for their eggs and meat until some time after 1000 BC, in the Iron Age. To the Persians, the rooster crowing at dawn heralded the return of light conquering darkness. (This lends a new meaning to Peter's betrayal of Jesus “before the cock crows.”) When chickens finally reached Europe, sometime between 1000 and 550 BC, they and their eggs were an exciting new food; Greeks sometimes called chickens "the Persian bird." Greeks and Romans often sacrificed chickens to their gods. Socrates, for example, asked his friends to sacrifice a cock to the god Asclepius for him as he was dying just after 400 BC.
In Egypt, chickens became a staple food even later, about 300 BC. After that, chickens slowly made their way south and west across Africa, reaching South Africa either from Egypt or through the work of Indian traders along the coast of East Africa, probably around 500 AD.
Chicks & Chickens, by Gail Gibbons (2003). Explains where chickens come from, and what they eat, and so on. For younger kids.
A Chicken in Every Pot: Global Recipes for the World's Most Popular Bird, by Kate Heyhoe (2003). Includes a brief history, and lots of recipes for chicken.
Much Depends on Dinner: The Extraordinary History and Mythology, Allure and Obsessions, Perils and Taboos, of an Ordinary Meal, by Margaret Visser (1999). Background on what you eat, including a chapter on chicken.
Food in Antiquity: A Survey of the Diet of Early Peoples, by Don and Patricia Brothwell (1998). Pretty specialized, but the book tells you where foods came from, and how they got to other places, and what people ate in antiquity. Not just Europe, either!