Until now, no species has had such a profound effect on shaping the Earth's biosphere as the humble broiler chicken.

I have a faint childhood memory of walking into a huge barn full of peeping yellow chicks for as far as I could see. The barn belonged to my mother's cousin and he let each child (there were four of us) choose a chick to take back to the house to play with. We gave those chicks rides on a toy train set and stroked their silky soft fuzz until it was time to return them to the barn. By the time we came for another visit, the chicks were gone and I was devastated.

That barnful of 50,000 chicks is a scene that can be found all around the world, thanks to humans' insatiable appetite for chicken. Broiler chickens, as birds raised for meat are called, are the most populous species of birds on Earth, with an estimated 23 billion on the planet at any given time. This is ten times more than the next most populous species (the red-billed quelea from sub-Saharan Africa, pop. 1.5 billion) and forty times more than the sparrow.

Humans breed and eat so much chicken that scientists say it will have a permanent effect on the geological record. Our era on Earth will be marked by a layer of chicken bones, along with plastic, concrete, and black carbon left over from burning fossil fuels.

A study published this week by the Royal Society describes the monster we've created in the past half-century of chicken breeding. The industry is fully reliant on technology, from egg incubator to slaughterhouse; and modern broilers – 90 percent of which are supplied by three companies, crippling genetic diversity among commercial breeds – would not survive without human support. From the study:

"The rapid growth of leg and breast muscle tissue leads to a relative decrease in the size of other organs such as the heart and lungs, which restricts their function and thus longevity. Changes in the centre of gravity of the body, reduced pelvic limb muscle mass and increased pectoral muscle mass cause poor locomotion and frequent lameness."



Gone are the days of pecking for bugs in the backyard. Modern broilers are now fed cereals such as maize, wheat, and barley that are commonly mixed with fishmeal and re-processed hatchery and broiler waste (egg shells, chicks and chickens).

YouTube/Screen capture

James Gorman reports for the the New York Times,

"The modern broiler chicken, with an average life until slaughter of a scant five to nine weeks, by various estimates, has five times the mass of its ancestor. It has a genetic mutation that makes it eat insatiably so that it gains weight rapidly... And because of its diet — heavy on grains and low on back yard seeds and bugs — its bones have a distinct chemical signature."



This means that geologists of the future will be able to recognize the bones belonging to Gallus gallus domesticus, further aided by the fact that chicken bones do not decompose easily when we toss them the way we do, encased in a plastic bag of other household trash. Instead of breaking down, they become fossilized. And, in Gorman's words, "there are so, so, so many bones."

The Royal Society paper does not take a moral stance on humans' treatment and consumption of chickens; it simply lays out the facts. But one can't help but feel uncomfortable when reading it. It's eerily reminiscent of a horror film script, describing a dystopian future where the ground is littered with the skeletal remains of creatures that were brutally dominated and eaten by another. Something about the sheer number of chickens consumed (65 billion annually) makes it deeply unsettling, too – a whole animal killed for every meal or two.

Read it, absorb it, and let it influence your food choices.