The Legacy of Human Civilisation Will Be Written in Chicken Bones

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We are living on the planet of the chickens. The broiler (meat) chicken now outweighs all wild birds put together by three to one. It is the most numerous vertebrate (not just bird) species on land, with 23 billion alive at any one time.

Across the world, chicken is the most commonly eaten meat. This has made it a vivid symbol of the Anthropocene – the proposed new geological epoch that marks the overwhelming impact of humans on the Earth’s surface geological processes.

The modern bird is now so changed from its ancestors, that its distinctive bones will undoubtedly become fossilised markers of the time when humans reigned the planet.

In a recent study together with colleagues, published by Royal Society Open Science, we compared the bones of the modern meat chicken to the bones of their ancestors dating back to Roman times.

Modern broiler chickens are radically different – they have a super-sized skeleton, distinct bone chemistry reflecting the homogeneity of their diet and significantly reduced genetic diversity.

This is because a modern broiler is twice the size of a chicken from the medieval period and they have been bred for one thing: rapid weight gain.

The speed of growth accelerated in the second half of the 20th century, with the modern broiler putting on weight five times faster than meat chickens from the 1950s.

The result is that at just five or six weeks old they are already slaughter ready. The evidence of this extraordinary growth is preserved in their bones, which are less dense and often deformed.

Poignantly, these birds cannot even be “rescued” from their factory farms – the strain of their enormous body means that if left to live even for another month, many birds die from heart or respiratory failure.

The modern chicken only exists in its current form due to human intervention. We have altered their genes to mutate the receptor which regulates their metabolism, which means that the birds are always hungry and so will eat and grow more rapidly.

Not only that, their entire life cycle is controlled by human technology. For example, the chickens are hatched in factories with computer-controlled temperature and humidity.

From one day old, they live under electric lights to maximise the hours they can feed. Their slaughter by machine allows for thousands of birds to be processed every hour.

Domesticated cows, pigs and sheep each number a billion or so, but it is chickens that are the most striking example of the modern biosphere.

Their bones are scattered across landfill sites and farms worldwide and therefore have a good chance of being preserved in the rock record as symbols of how our planet and its biosphere has changed from its pre-human state to one dominated by humans and our domesticated animals.

While humans have been selectively breeding chickens since their domestication in south-east Asia around 6,000 years ago, the speed and scale of change in the 20th century is far beyond anything observed in the past.

From the 1950s, the chicken population has risen in step with the rise in human population, as has our use of fossil fuels, plastics and other resources: now, this enfeebled and short-lived animal is more numerous than any bird species in Earth history.

What does the future hold? Right now, chicken consumption is on the rise. The meat is cheap, and many are moving away from beef and pork in order to reduce their greenhouse gas emissions.

Somehow we must adapt to a growing population in a world affected by climate change. But business as usual may be off the cards.

In a surprising move, the world’s largest chicken producers – Tyson Foods and Perdue Farms – are now investing in plant-based proteins. Does this mean the era of chickens could be over in a (geological) instant?

Nevertheless, the record of this human-engineered bird will be forever set in stone.

Any intelligent species which arises in the far future – hyper-evolved rats or octopuses, perhaps? – will have a puzzle on their hands (or tentacles) in trying to figure out how and why millions of these rapidly-evolved bones lie mixed with the technofossil debris of the huge petrified dumpsites we will leave behind.

As these future explorers reconstruct this bird – a creature far more helpless than the dodo – they may well rumble it too as a technological construct.

Chicken Bones May Be the Legacy of Our Time

A new study argues that the sheer abundance of chicken consumption, coupled with the strange skeletons of modern chickens, will leave a unique fingerprint


Some experts say we are now in the era of the “Anthropocene,” a term used to describe humans’ unprecedented influence on the planet. When our civilization is long gone, the Earth will continue to bear the effects of the time we spent here—effects like nuclear isotopes in sedimentary rock, and the fossilized remains of plastic on the ocean floor and concrete on land. But perhaps more than anything else, according to a new study, the great legacy of our time will be chicken bones. Lots and lots of chicken bones.


Writing in Royal Society Open Science, a team of researchers argues that the remains of domesticated chickens (Gallus gallus domecustis) will be a major and unique marker of our changing biosphere. For one thing, there are just so many of them. With a standing population of more than 22.7 billion, domesticated chickens far outnumber the world’s most abundant wild bird—the red-billed quelea, which has a population of about 1.5 billion. According to James Gorman of the New York Times, if you combined the mass of all these chickens, it would be greater than that of all other birds.

The world is home to such a huge number of chickens because humans can’t stop eating them. Chicken consumption is growing faster than the consumption of any other type of meat—more than 65 billion chickens were slaughtered in 2016 alone—and it is on pace to surpass pork soon as the world’s most consumed meat.

With an abundance of chicken dinners comes an abundance of chicken remains. In the wild, bird carcasses are prone to decay and are not often fossilized. But organic materials preserve well in landfills, which is where many chicken remains discarded by humans end up. Thus, these chicken bones don’t degrade, according to the study authors—they mummify. For this reason, lead study author Carys E. Bennett tells Sam Wong of New Scientist that chickens are “a potential future fossil of this age.”

The modern chicken’s strange and singular features also make it a good candidate to represent the current era of human-directed change. The domestication of chickens started around 8,000 years ago, but humans have come up with a number of innovations to feed our growing hunger for chicken products. Modern broiler chickens, which is the variety farmed for meat, are bred to be four or five times heavier than they were in the 1950s. They are transported to slaughterhouses once they reach an age of between five and seven weeks, which may seem like a short lifespan, but in reality, they would not be able to survive much longer.

“In one study, increasing their slaughter age from five weeks to nine weeks resulted in a sevenfold increase in mortality rate,” the study authors write. “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.”

These chickens are, unsurprisingly, unlike any the world has seen before. The study authors compared data on modern broilers to zooarchaeological information recorded by the Museum of London Archaeology. Today’s domestic chickens are descended from a bird called the red junglefowl, Gallus gallus, and related species that might have bread with G. gallus, Andrew Lawler and Jerry Adler explain for Smithsonian magazine. The researchers found that between the 14th and 17th centuries, domestication caused chickens to become noticeably larger than their wild progenitors. But those chickens had nothing on the fowls of today. “There has been a steady increase in growth rate since 1964,” the study authors write, “and the growth rate of modern broilers is now three times higher than that of the red junglefowl.”

So the next time you tuck into a plate of drumsticks or wings, remember: archaeologists of the future may one day be able to find and identify your meal.