The concept of the Anthropocene describes the current period in Earth’s history where humanity’s collective activities rival natural forces in shaping the planet’s systems. The name is derived from the Greek words anthropos (“human”) and cene (“new” or “recent”), signifying an epoch dominated by human influence. This idea suggests that the scale of human impact—from transforming land surfaces to altering atmospheric chemistry—is significant enough to leave a permanent, distinguishable mark in the geological record, potentially warranting classification as a new division of geologic time.
Defining the Human Epoch
A geological epoch is a subdivision of time defined by major changes in rock layers, such as shifts in mineral composition or the appearance of distinctive fossils. For the last 11,700 years, the planet has been in the Holocene Epoch, characterized by a stable climate that followed the last major ice age and allowed for human civilization to develop. The Anthropocene proposal suggests that human activity has fundamentally breached the stable environmental conditions that defined the Holocene.
The term was popularized in 2000 by Nobel laureate and atmospheric chemist Paul Crutzen. He argued that the influence of human behavior on Earth’s atmosphere was so profound that a new epoch was already underway. Crutzen, along with ecologist Eugene Stoermer, concluded that human impact had reached geological proportions. Unlike natural processes that unfold over millions of years, the changes driving the Anthropocene are occurring at an unprecedented speed and scale.
The Search for a Starting Date
Determining the exact start date for a proposed epoch has led to several competing hypotheses tied to major historical shifts in human civilization. One proposal suggests an “early Anthropocene” linked to the rise of agriculture and large-scale deforestation, which began altering atmospheric greenhouse gas levels thousands of years ago. Others point to the Industrial Revolution, dating the epoch’s commencement to the late 18th century, around 1784. This time was marked by the invention of the steam engine and the first significant global increases in carbon dioxide and methane concentrations recorded in ice cores.
The most widely supported proposal among stratigraphers focuses on the mid-20th century, specifically around 1950, coinciding with the “Great Acceleration.” This era saw an exponential surge in global population, industrial production, energy consumption, and environmental degradation. This preference is based on the requirement that a new epoch must be defined by a globally synchronous signal—a marker that appears worldwide in the geological record almost simultaneously. The mid-century boundary provides the clearest, most globally uniform evidence of a fundamental shift in the planet’s operating systems.
Physical Evidence of Human Impact
Proponents of the Anthropocene cite a range of globally distributed materials that serve as its signature in the planet’s rock strata. The most precise and globally synchronous marker is the “bomb spike,” a layer of artificial radionuclides—elements like plutonium-239 and cesium-137—resulting from the peak of atmospheric nuclear weapons testing in the mid-1950s. This radioactive fallout was distributed globally, settling in soils, sediments, and ice sheets, providing an unambiguous and precise time horizon.
Beyond the atomic signatures, human activities are creating entirely new classes of geological materials, often referred to as “technofossils.” The widespread distribution of plastics, which accumulate in oceans and break down into microplastic particles in sediments, will be a permanent marker in the future rock record. Similarly, the massive global production of concrete and aluminum, materials virtually unknown before the 20th century, will leave a distinct geochemical and structural signature in strata. Additionally, the combustion of fossil fuels has dispersed fly ash particles—microscopic, tough carbon spheres—across the globe.
The Ongoing Geological Debate
Formalization of a new geological epoch requires approval from the International Commission on Stratigraphy (ICS), the body responsible for the official Geologic Time Scale. The Anthropocene Working Group (AWG), an interdisciplinary team of scientists, was tasked with gathering the necessary evidence to propose the Anthropocene as a formal epoch following the Holocene. This process requires identifying a Global Boundary Stratotype Section and Point (GSSP), often called a “golden spike,” which is a single, physical location that captures the globally synchronous marker.
The AWG selected a sediment layer from Crawford Lake in Canada, which clearly records the mid-century plutonium spike, as the proposed GSSP. Despite years of research, the formal attempt to ratify the Anthropocene was rejected by a subcommission of the ICS in early 2024. Arguments against recognition included concerns that the proposed time interval is too short to qualify as an epoch, which typically spans millions of years, and that the changes are better classified as a geological “event.” The scientific debate continues to highlight humanity’s overwhelming and lasting impact on the Earth system.