https://www.theguardian.com/environment/2016/aug/31/domestic-chicken-anthropocene-humanity-influenced-epoch The chicken was first domesticated between 7,000 and 10,000 years ago from the red junglefowl, Gallus gallus, in southeast Asia. In the early 20th century, chickens were used mainly as a source of eggs. In the 1920s, this changed with the discovery of vitamin D, which meant that chickens could be housed indoors all year round, instead of being kept outside in the sun. In 1945, the US poultry company A&P held a competition to breed the "chicken of tomorrow", and the winner, Arbor Acres, now dominates the genetic stock of domestic chickens around the world. After the 2nd world war, large companies began to to integrate hatcheries, grain supplies and slaughtering facilities into battery farms. Vaccines and antibiotics allowed the birds to survive in confinement. By the 1950s, chickens that had taken 18 weeks to fatten up at the turn of the century now only took 6 weeks. At that time, British households ate about 1 million chickens. By 1965, this had gone up to 150 million. In 2020, chicken overtook pork as the world's most eaten meat. Prof Jan Zalasiewicz, a geologist at the University of Leicester and the chair of the Working Group on the Anthropocene, suggests that chicken fossils could be the defining characteristic of the Anthropocene.