The exact genetic lineage of the modern chicken farmed for meat and eggs has been extensively studied in recent years but there is no definitive answer as to where the modern chicken originated. It is known that fowl were known in ancient Egypt, but these birds appear to be different from modern poultry. It does seem that modern poultry descended from and were first domesticated in Asia. One recent study theorizes based on genetic data that the modern farm chicken originated in central Asia near modern day Pakistan, likely around a few thousand BC. From there, domestication spread throughout Asia and into Europe, including western Europe around 1000 BC. Curiously, early chicken domestication appears to have been cultivated mainly for the purposes of cockfighting. Using chicken as a major food source is a relatively recent development in society.
Ancient chicken farming techniques were simple, localized, and would today be called "free range." Modern chicken farming on an industrial scale is vastly different. First of all, chickens are divided based on those farmed for eggs versus those farmed for meat. Egg chickens (hens) are farmed in cages that are housed in buildings in long rows stacked on top of each other called battery cages. The eggs produced fall through the cage floor and collect in troughs for easy harvesting. Meat chickens (called broilers) are farmed in large, long buildings where they are raised and cultivated in batches numbering in the thousands. The chickens are strictly confined to the building and generally have less than 1 square foot of space apiece. The air is constantly ventilated and food and water are distributed through an automated system. Some systems even keep the chickens in darkness to keep them more docile. One consistency to these modern industrial farming techniques is the fact that the chickens are highly confined to indoor areas with no time for free movement outdoors. This has led many animal rights groups to protest these methods and champion the free range techniques that smaller more localized farms employ.