How the domestic chicken rose to define the Anthropocene

quarta-feira, 31 de agosto de 2016

The domestic chicken is set to play an epoch-defining role for humanity, as its bones could become the key fossil evidence for the dawn of the age in which humankind came to dominate the planet.

On Monday, an expert group announced that a new geological epoch, the Anthropocene, should be declared. But the key to defining a geological age is finding global physical evidence of the transition that will be preserved for future geologists, and the chubby modern chicken eaten worldwide is a prime candidate.

Prof Jan Zalasiewicz, a geologist at the University of Leicester and the chair of the Working Group on the Anthropocene, said: “It has become the world’s most common bird. It has been fossilised in thousands of landfill sites and on street corners around the world.”

Global consumption of chicken expanded enormously as factory farming took off after the second world war, at a time when industrialisation and population growth made humanity the planet’s primary driving force. Chickens are the world’s most populous bird, with almost 60 billion killed a year.

The chicken’s rise to global avian domination took off in 1945, when the the US government and major poultry company A&P announced a competition to breed the “chicken of tomorrow”, a bird that would grow fatter and more quickly than ever. The winner, called Arbor Acres, still dominates the genetic stock of domestic chickens around the world.

The chicken was first domesticated between 7,000 and 10,000 years ago from the red junglefowl, Gallus gallus, native to south-east Asia. The wild bird was a poor flier, making it the perfect catch. Over subsequent millennia, the bird was carried all over the world, giving it the global presence so useful to the Anthropocene geologists.

However, even in the early 20th century, chickens were primarily sources of eggs. Male birds and exhausted egg layers were eaten, but only as a luxury on special occasions. The transition to the ubiquitous meat of today began with the discovery of vitamin D in the 1920s, meaning that the birds could be housed indoors all year round, rather than let out in the summer to soak up sunlight.

After the second world war, large companies, particularly in the US, began to integrate hatcheries, grain supplies and slaughtering facilities into enormous battery farms. Vaccines and antibiotics enabled the birds to survive the close confinement and, by the 1950s, chickens that had taken 18 weeks to fatten up at the turn of the 20th century took six weeks to be ready for the chop.

In 1950, British households ate about 1 million chickens, but by 1965, they gobbled up 150 million. Another result of industrialisation was the greatest decline in domestic chicken diversity in history, with half or more of all ancestral chicken breeds now lost. This makes the bird even more suitable as the type fossil of the Anthropocene. The same chicken leaves bones, bigger and differently shaped to its ancestors, all over the world.