It started with a post in my feed—about who rules the Earth by mass. The author was breaking down biomass by species and casually mentioned that roughly two-thirds of the total mass of all the birds on the planet consists of fast-food birds. What caught me was not the number but the phrase itself: it turns a biological species into a food-service category.
We’re talking about the broiler—a chicken raised for meat. Not a village hen, not the kind that runs around a yard: the modern broiler is a product of industrial breeding, and its body is built in such a way that it cannot live on its own. This is not an exaggeration: the bird physically cannot survive without humans—without feeders, heating, a veterinary schedule, and constant supervision.
Here is what’s interesting: such a chicken has a chance of becoming a fossil by which the very distant future recognizes our era. Not plastic, not concrete, not a radioactive trace, but the bone from a drumstick we used to eat with lunch.
The idea that the domestic chicken could serve as a marker of a new geological epoch was proposed in 2018 by a group of paleobiologists in the journal Royal Society Open Science. The argument is not that there are lots of chickens—though there really are a lot of them—but that this bird can be identified by its bones, and identified as something new. The skeleton, pathologies, bone chemistry, and genetics of the modern broiler are measurably different from anything that came before. Taken together, the authors proposed treating the broiler as a separate “morphospecies”—a form that never existed in nature.
The scale really is decisive here. The population of domestic chickens is almost certainly the largest population of any bird in Earth’s history, and it is an order of magnitude larger than that of any wild bird. For comparison: the most numerous wild bird is the red-billed quelea, with around 1.5 billion; the house sparrow has roughly half a billion; the rock pigeon, a quarter-billion. The combined mass of broilers alone exceeds the mass of every other bird on the planet put together. Chickens stopped being one species among many long ago—they became the background.
This is the right moment to admit that the numbers in the sources are not entirely tidy, and it is more honest to show that than conceal it. The 2018 article speaks of 22.7 billion live chickens on the planet. Geologists Sarah Gabbott and Jan Zalasiewicz, in their 2025 book, put the figure at 25 billion. And current statistics from the UN Food and Agriculture Organization for 2024 give nearly 29.6 billion birds.
The discrepancy has a simple explanation: the sources count different things in different years—birds alive at a given moment or birds sold over a year, all domestic poultry or chickens alone. There is also a separate number: slaughter. According to the same FAO data, 6.6 billion chickens were slaughtered worldwide in 1961, 40.5 billion in 2000, and 78.5 billion in 2024. At the same point: 1.5 billion pigs and 0.3 billion cattle. By headcount, chickens account for more than 95% of all slaughter. Rounded off: around eighty billion bird skeletons a year that go somewhere—onto store shelves, into freezers, into waste, into the ground.
This is the fact I find most powerful in this whole story. Since the middle of the twentieth century, the mass of an individual commercial bird has increased roughly fivefold. Paleobiologist Jan Zalasiewicz put it this way: the emergence of a new animal form normally takes millions of years, but here a few decades were enough.
The usual starting point is the 1948 “Chicken of Tomorrow” contest, sponsored by the A&P grocery chain together with the U.S. Department of Agriculture. The chain’s motives were not entirely noble: three years before the contest, A&P had been convicted of restraining competition, and a large-scale initiative helped repair its reputation. The contest ran for three years, breeders from 44 states took part, and the final was held at the University of Delaware. The winners were Henry Saglio’s White Plymouth Rocks and the Vantress cross with Red Cornish; Saglio’s line then spread around the world and forms the basis of most modern breeds, including Cobb 500.
What followed was pure selection arithmetic. From 1957 to 2005, broiler growth rate increased by more than 400%, while the feed required per kilogram of weight gain fell by half. Breast-muscle yield rose by around 80% over the same half-century. Meat went from a rare Sunday dish to the cheapest protein on the planet: in the United States, per-capita chicken consumption rose from 9.4 kilograms in 1950 to 39.2 kilograms in 2005.
The other side of the same race is that modern broilers commonly develop muscle defects with almost culinary names: “wooden breast,” “white striping,” “spaghetti meat.” This is not cosmetic. The muscle grows faster than it can be supplied with blood vessels, hypoxia and inflammation begin inside it, and proteins do not have time to fold properly.
The bird bred for its breast physically cannot cope with its own breast. The skeleton cannot keep pace with the mass either: leg deformities and bone disorders are common in broilers, and the skeleton itself is not strong enough for the body that has grown around it. Hence the hard dependence on humans: without care, the chicken simply does not live long enough to reach market weight. Gabbott and Zalasiewicz describe it concisely: bred to live fast and die young and fat.
There is another layer here that I did not expect to find when I began digging. All this genetic diversity in broilers rests on two suppliers of breeding stock. Aviagen, owned by the German family group EW Group, is the world’s largest broiler-breeding company, with around 44% of the global market and operations in more than 85 countries. Cobb-Vantress, founded back in 1916 and owned by Tyson Foods since 1994, operates in more than 120 countries.
They do not sell chicks but parent lines—the great-great-grandmothers and great-great-grandfathers of commercial birds. Almost all of the world’s chicken passes through this narrow neck: researchers explicitly call the situation a “global genetic bottleneck.” Billions of identical birds, bred on two continents—this is no longer farming in the familiar sense, but managed biology on an industrial scale.
It would seem that the rest is a technicality: if there is a convincing marker, declare a new geological epoch. But in March 2024, the International Union of Geological Sciences definitively rejected the proposal. The working group had prepared it for fifteen years, chose Crawford Lake in Ontario, Canada, as the type section, and selected radioactive isotopes scattered across the planet after hydrogen-bomb tests as the best marker. The Subcommission on Quaternary Stratigraphy rejected the proposal by 12 votes to 4, while the chairs of seventeen subcommissions confirmed the rejection almost unanimously: 15 votes, with one abstention. No appeal is provided for.
The reasons for rejection are interesting in themselves. Opponents pointed out that humanity’s impact on Earth began long before 1952—with agriculture and the Industrial Revolution—and that a unit on the geological timescale shorter than a human life looks absurd, since most such units span thousands and millions of years. Another objection was voiced separately: the signal of chicken bones, like that of plastic and concrete, is smeared across time and space, and cannot be pinned to a single date. In a letter to The Guardian, geologist Matthew Edgeworth put it bluntly: trying to fit it into a rigid date “distorts understanding.”
Jan Zalasiewicz, one of the epoch’s leading advocates, called the decision a missed opportunity and insisted that the planet had left its natural regime abruptly and irreversibly, and that the signals of this in the rocks are myriad. The Anthropocene did not become a formal unit of the timescale, but it remains a working word for describing the human trace. The scale itself proved too slow for what happened within a single human generation.
The answer to the question from the hook turns out to be dry. Yes, the broiler has every chance of entering the geological record as the most conspicuous bird of all time—by volume, by form, by the chemistry of its bones. No, no epoch was named after its bones: the signal is too fast and too diffuse for a strict scale accustomed to measuring time in millions of years.
And that future fame does not make life any easier for the living bird. A body bred for its breast can barely carry itself—and a creature like that does not live without humans. Humans are its habitat.