The broiler bird stands as the quintessential emblem of today’s meat-production complex. In 1925, the average fowl sent to the knife was 112 days old, consuming 4.7 pounds of feed for every pound of live weight, and tipping the scales at 2.5 pounds when it was slaughtered. By contrast, a modern industrially raised chicken survives for about 47 days, requires roughly 1.69 pounds of feed per pound gained, and attains a weight of about 6.57 pounds. The bird’s oversized breast makes the frame unstable. Once growth is complete, chickens are shoveled (or scooped by a harvester likened to a Zamboni) into cartons and sent to a processing plant, where electronarcosis reaches its mechanized extreme: the birds are strapped to conveyor lines, flipped head over heels, immersed headfirst in water, and then rinsed in an electric bath. The stunned creatures are then decapitated. Chickens are killed by the billions (roughly seventy-five billion annually), and poultry has become the globe’s most-consumed meat.
If pondering extraterrestrial visitors ever visited Earth, they might marvel at a planet that sustains such an astonishing population of chickens. Chickens are the most numerous bird species by a factor of ten, numbering about four for every person. We keep them warm, feed them, and govern their enormous piles of waste. If evolution keeps score by genetic replication, the chicken has run far ahead, though, as one scientist put it, “the most heavily qualified of victories” amounts to merely staying alive long enough to be turned into a nugget.
Whether or not aliens ever contemplate our intimate entanglement with the chicken, someone surely will puzzle over it. Millions of years hence, fossilized remains of the artificially bred broiler could stand as a geological marker of human ascendancy. Bird bones, in general, fossilize poorly. Future paleontologists would need very lucky timing and precise instruments to detect the wave of avian extinctions since the late Pleistocene—La Brea storks, moas, dodos, auks, passenger pigeons, Mariana mallards, and countless others. The lesser prairie chicken would vanish from view. Yet the abrupt rise of the improbably shaped, hyperabundant broiler will be unmistakable because the bone fragments of our appetite—drumsticks, wing bones, and oversized sternums—will accumulate in landfills. There, in these oxygen-starved dumps, their bones will mummify. They will sink beneath the Earth’s surface, where they will endure in the rock until the day some distant sun finally consumes this tiny life-bearing speck of cosmic dust.
The broiler chicken will be an indelible geological signature of humanity, calling out to future eons, like graffiti scratched into a diner table, that we were here once, and we feasted.
Mostly hidden from daily view, the machinery behind white-meat production—a planetary-scale chemical and metabolic system—will linger as a trace of human presence in Earth’s historical record. The broiler chicken will be a lasting geological signature of humanity, speaking to future ages, like graffiti carved into a diner table, that we were here once, and we feasted.
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The broiler chicken might serve as the mascot of the Anthropocene. The term Anthropocene—combining “anthropo” (human) and “cene” (new)—designates a proposed new geological epoch meant to succeed the relatively stable Holocene. The standard scale of Earth’s history is a stratigraphic chart, a layered timeline geologists use to separate deep time into eons, eras, periods, and epochs based on shifts in Earth’s conditions, climate, and chemistry. Our species emerged during the cold Pleistocene, thrived in the mild Holocene, and may have pushed the planet into a new era defined by human dominance.
The notion of the Anthropocene serves as a framework for understanding humanity’s impact on global biodiversity. The term is relatively young—born in 2000 during a meeting of the International Geosphere Biosphere Programme in Cuernavaca, Mexico—when the Nobel laureate atmospheric chemist Paul Crutzen asked to speak. The meeting’s chair recalled the moment: “As Paul began to recite with quiet urgency the extraordinary planetary changes triggered by James Watt’s steam-engine in 1784, the recital took on a shape. The sum of these changes was a planetary-scale transformation. This moment should mark the start of a new epoch: The Anthropocene.” Crutzen’s appeal stunned the assembly of scientists for a moment. Yet in the twenty-five years since, the discussion has persisted relentlessly.
The Anthropocene is a radical proposal. It asserts that our 11,700-year interglacial—the Holocene—has ended, and that we have irreversibly entered a new geological epoch. In this epoch, the dynamics of the Earth System are shaped by human influence, and our fingerprints are etched permanently into the planet’s crust. The official timetable for Earth’s history rests in the hands of practicing geologists—the successors to Lyell—who have historically treated the task of adding an epoch to the geological record with careful caution.
In 2024, after more than a decade of deliberation, and despite the recommendation of its own Anthropocene Working Group, the Subcommission on Quaternary Stratigraphy decided against formally recognizing the Anthropocene as a new epoch. This cautious path was chosen, but it does not erase the reality: the term has become indispensable and inescapable among scientists, scholars, and the public alike. The Anthropocene has begun.
The debate about stratigraphic timing is more than a scientific squabble. The Anthropocene provides a frame for pondering humanity’s role in Earth’s history. At its core, the idea reiterates that Earth is not a passive rock but a connected system shaped by life and by nonliving processes alike. The planet’s atmosphere, oceans, soils, and climate are all products of living activity, and our species now dominates the functioning of the entire planetary system. The notion helps us recognize that humanity’s impact on biodiversity, both now and into the foreseeable future, is inseparable from global-scale dynamics.
A geological epoch needs a starting point, and while Crutzen initially proposed 1784, the growing consensus now points to a mid‑twentieth‑century marker—often linked to the postwar era known as the Great Acceleration. This period offers a clear divider in the geological record: chicken bones and plastic waste, shrinking forests, synthetic fertilizers, and the residues of nuclear weapons tests all signal a transformed world. Any far-future geologist examining sediment cores would find a thin layer of radioactive fallout—a precise timestamp marking a world forever altered—an undeniable technofossil boundary that signals humanity’s broader supremacy.
The Great Acceleration refers to the dramatic rise after 1950 in human populations, economic activity, technological progress, and resource consumption, all of which magnified our influence on the Earth System and its biosphere. Consider population dynamics: about 1.6 billion people inhabited the globe in 1900; by 1950 this figure stood at roughly 2.5 billion; today it exceeds 8 billion and continues to climb. In short, global population more than tripled within a single lifetime. This growth cycle rested on deregulated ecology, removing barriers that once kept numbers in check. The decline of infectious disease—through advances in medicine, sanitation, and public health—erased one of the oldest limits on growth. In the mid-twentieth century, lifesaving technologies spread across the world. With microbial parasites kept at bay, human beings could multiply with less natural check. It’s not a simple metaphor of breeding like rabbits; it’s that we stopped dying as readily as flies.
Populations in wild ecosystems are also governed by the availability of resources, and our triumph over disease would have had little effect without sufficient nourishment. At the start of the twentieth century, fears of famine were reasonable; by the end of the century, however, the threat of widespread hunger had largely receded (apart from the tragedies born of war and misgovernance, a caveat not to be ignored). A global food crisis was averted thanks to rapid innovation. The Haber-Bosch process allowed us to extract inert nitrogen from the air and convert it into reactive fertilizer. This invention—the mass production of ammonia, far more efficient than digging up guano or mining bone—eliminated the most critical nutrient bottleneck in global agriculture.
Around the middle of the century, agronomists introduced high-yield, fast-maturing crop varieties such as wheat and rice through the Green Revolution. Yields per hectare surged across Asia, Latin America, and Africa, accompanied by a vast expansion of cultivated land. In the postwar decades, humans seized ecosystems at a breakneck pace—forests were cleared, prairies were plowed, wetlands drained. More tropical forest was cleared in the late twentieth century than in any earlier era, with roughly one-sixth of the Amazon rainforest—an area the size of France—disappearing in the last fifty years alone.
More food meant more people and more of the animals we prefer to eat. Today, the actual mass of our species (about 60 million tons of carbon) and our domesticated animals (mainly cattle and pigs, around 100 million tons) far exceeds that of all wild mammals (roughly under 10 million tons) on land. By one reckoning, humans and our domesticated animals now account for about 94 percent of all terrestrial mammal biomass on Earth, leaving a mere 6 percent for all wild species. We have tipped the biosphere’s scales toward ourselves. And it isn’t just human bodies: the material “stuff” produced by civilization now surpasses the total dry mass of all living organisms on the planet. A recent study estimated that by 2020 the mass of human-made materials (concrete, steel, asphalt, plastic, and the like) reached about 1.1 teratons, exceeding the total dry weight of all living things (roughly 1.0 teraton) on Earth.
Humanity has become a literal Earth-System force, moving substantial portions of the planet’s outer shell. We push soil and rock, redirect rivers, blast mountains, and cover the world with artificial matter. We displace more earth and rock each year than all natural erosion processes combined. Mining operations have grown more extensive as greater amounts of overburden must be shifted to reach desired minerals and metals; for example, to obtain the average four‑gram wedding band, roughly twelve tons of rock must be mined. Year after year, we build new houses, cars, roads, factories, and towers. An individual today can be responsible for producing their own weight in synthetic material every week—although this glosses over the vast disparities in consumption that bedevil any simple average.
In the Anthropocene, we have inverted the fundamental ecological predicament of our species: from scarcity to surplus, from hunger to glut.
Just as Newtonian mechanics powered the First Industrial Revolution, electromagnetism and chemistry propelled the Second, driving the era of the Great Acceleration. Fundamental science paired with applied technological innovation. Electricity lit cities, transformed manufacturing, and disrupted the rhythms of life. Telecommunication connected people in an ever louder, broader network. The internal combustion engine finally toppled the long era of horse power.
Most notably, advances in chemistry provided us with a new degree of control over other living beings. The examples of vitamin D and synthetic fertilizer already hint at this trajectory. Yet we often underestimate chemistry, partly because the modern history reads like the fine print on a shampoo bottle. To avert discouragement, the chapter’s protagonists include cholecalciferol, ammonia, neonicotinoids, polyethylene, 17α-methyltestosterone, and diclofenac. (If any of these appear in your shampoo, consider changing brands.) It takes a broader perspective to grasp how extraordinary these substances are.
Nature, across four billion years of evolution, has learned to assemble remarkable molecules. Biological evolution acts as a blind but tireless experimental chemist. Some of its feats—the choreography of protein folding, the ribosome’s efficiency, the construction of sugars from sunlight—are to be admired. Yet evolution follows constraints; it builds incrementally on what exists, solving a complex puzzle one incremental twist at a time. We, by contrast, plunge to the atomic level and start anew. We are catching up and, in some respects, surpassing nature with synthetic materials—plastics, pesticides, and pharmaceuticals. Chemistry is a godlike craft, capable of both creation and destruction.
One odd indicator of these powers can be seen in the diversity of Earth’s minerals. Billions of years ago, the planet housed only a handful of primary minerals—the basic building blocks formed in ancient stars and scattered by supernovae. Those grains coalesced into the earliest planetesimals. Inside those primordial worlds, heat and pressure yielded roughly 250 distinct minerals, which combined to form early Earth. Then, through volcanic upheaval and deep-earth chemistry, more than a thousand new minerals emerged. Then life began. Microbes fed on nutrients, exhaled waste, and altered the chemistry of oceans and rocks. Photosynthesis released oxygen. Life reshaped geology itself.
By the time multicellular organisms appeared, Earth boasted nearly five thousand minerals—an abundance unmatched anywhere else in the solar system. And then came us. The International Mineralogical Association—keeper of the mineral registry—refuses to count synthetic minerals in its official tally (it recognizes only natural or geologically occurring stable inorganic crystals). Yet a mineral is a mineral, whether grown in a supernova or in a lab. Objectively, humanity has added more than three hundred thousand minerals to Earth. Wafers of monocrystalline silicon. Yttrium aluminum garnet in lasers. Boron carbide, among the hardest substances after diamond, embedded in body armor. These too will endure in the crust, as enduring witnesses to human agency.
Our command of synthetic chemistry resembles a second form of mastery over fire, a landmark—biological and geological—in Earth’s history. Synthesis also consumes vast energy, and energy consumption underpins modern growth, a defining feature of the Great Acceleration. Coal powered early industrialization and was soon joined by oil and natural gas: fossil sunlight captured by ancient plankton and stored as fuels. Over time, contributions from nuclear fission and solar, hydro, and wind energy have joined the mix. Since 1950, humanity has consumed twenty-two zettajoules of energy. In plain terms, during the last three human generations we have used more energy than in the entire Holocene, a span of more than ten thousand years. Whatever year you read this, it likely marks the peak in human energy consumption to date.
In the Anthropocene, we have inverted the essential ecological dilemma of our species: from scarcity to abundance, from hunger to surplus. This transformation has made us a dominant force within the Earth System. It is not difficult to see how human influence on the planet has rewritten its biodiversity narrative: the megafaunal extinctions that shifted carbon and methane fluxes; deforestation delaying the onset of the next ice age; industrialization burning primeval forests. But these were only glimpses of the kind of sway humans now command. And that sway is unprecedented, not requiring Lyell’s peculiar sense of deep time to justify it as kainos (‑cene, “recent”). In mere a few human generations, the Great Acceleration has propelled the world into a new geological epoch.
The Anthropocene is destined to leave a permanent geological and paleontological boundary in the rock record. Future geologists will find clear evidence of Earth-System agency—the material traces of a planet dominated by a single species. Future paleontologists will recognize a decisive pivot in the evolutionary archive. That there will be a fossil signature of the Anthropocene is already a settled matter and irreversible; what that signal will ultimately convey remains uncertain and to be decided.
Whether or not we spark a new mass extinction, our influence on the biosphere is inseparable from the Anthropocene, a planetary, systemic phenomenon that stretches from pole to tropics, altering life on land and sea and affecting the fate of countless species, large and small.
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From The Last Animal: Human History and the Fate of Life on Earth from the Ice Age to the Sixth Extinction by Kyle Harper. Copyright © 2026. Available from Princeton University Press.
