The domestic chicken, the most populous bird on Earth, traces its lineage to a single domestication event that occurred approximately 8,000 years ago in Southeast Asia, a timeline that genomic studies have pushed back significantly from previous estimates of 5,400 years. This ancient process began not in a barn, but through the collection of eggs from the wild red junglefowl, which were then hatched and reared by early human communities in what is now southwestern China, northern Thailand, and Myanmar. While modern commercial breeds like the White Leghorn possess a complex mosaic of divergent ancestries inherited from various subspecies of junglefowl, the original domestication was a singular event that spread rapidly across the region. Archaeological evidence confirms the presence of domestic chickens in Southeast Asia well before 6000 BC, with the species reaching China by 6000 BC and India by 2000 BC. These birds were not initially raised for food; instead, they were first utilized for cockfighting, a practice that formed part of the cultures of ancient India, China, Persia, Greece, and Rome, where large sums of money were won or lost on the outcome of encounters between two mature males. The transition from fighting to farming was gradual, as people realized the advantages of having a captive-bred source of eggs and meat, leading to centuries of selective breeding for fast growth, egg-laying ability, and docility. By 2000 BC, chickens had reached the Indus Valley, and 250 years later, they arrived in Egypt, where they were still used for fighting and regarded as symbols of fertility. The Romans used them in divination, and the Egyptians made a breakthrough when they learned the difficult technique of artificial incubation, a skill that allowed the keeping of chickens to spread around the world for the production of food.
The Silent Revolution of Waterfowl
While chickens dominated the ancient world, the domestication of ducks took place in the Far East at least 1,500 years earlier than in the West, with clay models of ducks found in China dating back to 4000 BC indicating the domestication of the mallard during the Yangshao culture. Unlike chickens, which were initially valued for their combative nature, ducks were integrated into agriculture much later in Western Europe, not appearing in agricultural texts until about 810 AD when they began to be mentioned alongside geese, chickens, and peafowl as being used for rental payments made by tenants to landowners. The mallard, the ancestor of all breeds of domestic duck except the Muscovy duck, was farmed mainly for its meat, eggs, and down, with the Pekin duck emerging as the most common commercial breed in the United Kingdom and the United States. This breed can lay 200 eggs a year and reach a weight of 4.5 kilograms in just 44 days, yet ducks remain less popular than chickens in the Western world because the latter produce larger quantities of white, lean meat and are easier to keep intensively. In the East, however, ducks are more popular than chickens and are mostly still herded in the traditional way, selected for their ability to find sufficient food in harvested rice fields and other wet environments. The process of raising ducks involves a unique social structure, as they are social birds that prefer to live and move around together in groups, keeping their plumage waterproof by preening, a process that spreads the secretions of the preen gland over their feathers. Despite their early domestication, geese have never gained the commercial importance of chickens and ducks, with the greylag goose domesticated by the Egyptians at least 3,000 years ago and the swan goose domesticated in Siberia about a thousand years later.
The history of poultry is not just a story of white meat and eggs, but also of the dark, protein-rich flesh of geese and the unique dietary practices that surround them. The greylag goose, domesticated by the Egyptians, and the swan goose, domesticated in Siberia, hybridized to create the Chinese goose, which is more aggressive and noisy than other geese and can be used as a guard animal to warn of intruders. These birds are much larger than their wild counterparts, tending to have thick necks, an upright posture, and large bodies with broad rear ends, with the greylag-derived birds being large and fleshy and used for meat, while the Chinese geese have smaller frames and are mainly used for egg production. The fine down of both is valued for use in pillows and padded garments, and they forage on grass and weeds, supplementing this with small invertebrates, one of the attractions of rearing geese being their ability to grow and thrive on a grass-based system. In some countries, geese and ducks are force-fed to produce livers with an exceptionally high fat content for the production of foie gras, with over 75% of world production of this product occurring in France, with lesser industries in Hungary and Bulgaria and a growing production in China. The flesh of meat geese is dark-colored and high in protein, but they deposit fat subcutaneously, although this fat contains mostly monounsaturated fatty acids, and the birds are killed either around 10 or about 24 weeks, between which ages problems with dressing the carcase occur because of the presence of developing pin feathers. The history of poultry is also a history of the turkey, a large bird whose nearest relatives are the pheasant and the guineafowl, with the modern domesticated turkey descended from one of six subspecies of wild turkey found in the present Mexican states of Jalisco, Guerrero, and Veracruz. Pre-Aztec tribes in south-central Mexico first domesticated the bird around 800 BC, and Pueblo Indians inhabiting the Colorado Plateau in the United States did likewise around 200 BC, using the feathers for robes, blankets, and ceremonial purposes before they became an important food source more than 1,000 years later.
The Industrial Machine
The transformation of poultry from a small-scale family livelihood to a global industrial machine began in the 19th century, with chickens being kept on a larger scale in about 1800 and modern high-output poultry farms being present in the United Kingdom from around 1920 and becoming established in the United States soon after the Second World War. By the mid-20th century, the poultry meat-producing industry was of greater importance than the egg-laying industry, and today, worldwide, more chickens are kept than any other type of poultry, with over 50 billion birds being raised each year as a source of meat and eggs. The most intensive system for egg-laying chickens is battery cages, often set in multiple tiers, where several birds share a small cage which restricts their ability to move around and behave in a normal manner, and these cages have been illegal in the EU since the 1st of January 2012. Chickens raised intensively for their meat are known as broilers, breeds that have been developed to grow to an acceptable carcass size in six weeks or less, but their legs cannot always support their weight and their hearts and respiratory systems may not be able to supply enough oxygen to their developing muscles. Mortality rates at 1% are much higher than for less-intensively reared laying birds which take 18 weeks to reach similar weights, and processing the birds is done automatically with conveyor-belt efficiency, where they are hung by their feet, stunned, killed, bled, scalded, plucked, have their heads and feet removed, eviscerated, washed, chilled, drained, weighed, and packed, all within the course of little over two hours. Both intensive and free-range farming have animal welfare concerns, with cannibalism, feather pecking, and vent pecking being common in intensive systems, and diseases can also be common and spread rapidly through the flock, while in extensive systems, the birds are exposed to adverse weather conditions and are vulnerable to predators and disease-carrying wild birds.
The Science of Survival
The relationship between humans and poultry extends beyond mere consumption into the realm of medical science, where the humble chicken egg plays a critical role in the production of life-saving vaccines. Millions of eggs are used each year to generate the annual flu vaccine requirements, a complex process that takes about six months after the decision is made as to what strains of virus to include in the new vaccine, and a problem with using eggs for this purpose is that people with egg allergies are unable to be immunised, but this disadvantage may be overcome as new techniques for cell-based rather than egg-based culture become available. Cell-based culture will also be useful in a pandemic when it may be difficult to acquire a sufficiently large quantity of suitable sterile, fertile eggs, and the use of eggs for vaccine production highlights the dual nature of poultry as both a food source and a medical tool. However, the consumption of poultry also carries risks, as a 2011 study by the Translational Genomics Research Institute showed that 47% of the meat and poultry sold in United States grocery stores was contaminated with Staphylococcus aureus, and 52% of the bacteria concerned showed resistance to at least three groups of antibiotics. Thorough cooking of the product would kill these bacteria, but a risk of cross-contamination from improper handling of the raw product is still present, and some risk is present for consumers of poultry meat and eggs to bacterial infections such as Salmonella and Campylobacter. Poultry products may become contaminated by these bacteria during handling, processing, marketing, or storage, resulting in food-borne illness if the product is improperly cooked or handled, and in general, avian influenza is a disease of birds caused by bird-specific influenza A virus that is not normally transferred to people, however, people in contact with live poultry are at the greatest risk of becoming infected with the virus and this is of particular concern in areas such as Southeast Asia, where the disease is endemic in the wild bird population and domestic poultry can become infected.
The Global Meat Economy
Poultry is the second most widely eaten type of meat in the world, accounting for about 30% of total meat production worldwide compared to pork at 38%, with 16 billion birds raised annually for consumption, more than half of these in industrialized, factory-like production units. The largest producers of poultry meat were the United States, accounting for 20% of global production, followed by China at 16.6%, Brazil at 15.1%, and the European Union at 11.3%, with two distinct models of production: the European Union supply chain model, which seeks to supply products which can be traced back to the farm of origin, and the United States model, which turns the product into a commodity. World production of duck meat was about 4.2 million tonnes in 2011, with China producing two thirds of the total, some 1.7 billion birds, and other notable duck-producing countries in the Far East include Vietnam, Thailand, Malaysia, Myanmar, Indonesia, and South Korea, with France being the largest producer in the West, followed by other EU nations and North America. China was also by far the largest producer of goose and guinea fowl meat, with a 94% share of the 2.6 million tonne global market, and global egg production was expected to reach 65.5 million tonnes in 2013, surpassing all previous years, with egg production growing globally at around 2% per year between 2000 and 2010, but since then growth has slowed down to nearer 1%. In 2018, egg production reached 76.7 million tonnes, a huge 24% growth since 2008, and the trade in poultry is a complex web of economic, cultural, and logistical factors that shape the global food supply. The largest producers of poultry meat were the United States, accounting for 20% of global production, followed by China at 16.6%, Brazil at 15.1%, and the European Union at 11.3%, with two distinct models of production: the European Union supply chain model, which seeks to supply products which can be traced back to the farm of origin, and the United States model, which turns the product into a commodity.
The Anatomy of Appetite
The culinary history of poultry is defined by the anatomical differences between the white and dark meat of birds, with the meatiest parts of a bird being the flight muscles on its chest, called breast meat, and the walking muscles on the legs, called the thigh and drumstick. The wings are also eaten, with Buffalo wings being a popular example in the United States, and may be split into three segments, the meatier drumette, the wingette, and the wing tip, and in Japan, the wing is frequently separated, and these parts are referred to as teba-moto and teba-saki. Dark meat, which avian myologists refer to as red muscle, is used for sustained activity, chiefly walking, in the case of a chicken, and the dark color comes from the protein myoglobin, which plays a key role in oxygen uptake and storage within cells, while white muscle, in contrast, is suitable only for short bursts of activity such as, for chickens, flying. Thus, the chicken's leg and thigh meat are dark, while its breast meat, which makes up the primary flight muscles, is white, and other birds with breast muscle more suitable for sustained flight, such as ducks and geese, have red muscle and therefore dark meat throughout. Some cuts of meat including poultry expose the microscopic regular structure of intracellular muscle fibrils which can diffract light and produce iridescent colors, an optical phenomenon sometimes called structural coloration, and the health benefits of poultry are also significant, as poultry meat and eggs provide nutritionally beneficial food containing protein of high quality, accompanied by low levels of fat which have a favorable mix of fatty acids. Chicken meat contains about two to three times as much polyunsaturated fat as most types of red meat when measured by weight, and for boneless, skinless chicken breast, the amount is much lower, with 100 grams of raw chicken breast containing 3.6 grams of fat and 31 grams of protein, compared to 100 grams of fat and 26 grams of protein for the same portion of raw beef flank steak.