''Anthropocene'' is a term that has been used to refer to the period of time during which
humanity has become a planetary force of change. It appears in scientific and social discourse, especially with respect to accelerating geophysical and biochemical changes that characterize the 20th and 21st centuries on Earth. Originally a proposal for a new
geological epoch following the
Holocene
The Holocene () is the current geologic time scale, geological epoch, beginning approximately 11,700 years ago. It follows the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene to ...
, it was rejected as such in 2024 by the
International Commission on Stratigraphy
The International Commission on Stratigraphy (ICS), sometimes unofficially referred to as the International Stratigraphic Commission, is a daughter or major subcommittee grade scientific organization that concerns itself with stratigraphy, strati ...
(ICS) and the
International Union of Geological Sciences
The International Union of Geological Sciences (IUGS) is an international non-governmental organization devoted to global cooperation in the field of geology. As of 2023, it represents more than 1 million geoscientists around the world.
About
Fo ...
(IUGS).
The term has been used in research relating to Earth's
water
Water is an inorganic compound with the chemical formula . It is a transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance. It is the main constituent of Earth's hydrosphere and the fluids of all known liv ...
,
geology
Geology (). is a branch of natural science concerned with the Earth and other astronomical objects, the rocks of which they are composed, and the processes by which they change over time. Modern geology significantly overlaps all other Earth ...
,
geomorphology
Geomorphology () is the scientific study of the origin and evolution of topographic and bathymetric features generated by physical, chemical or biological processes operating at or near Earth's surface. Geomorphologists seek to understand wh ...
,
landscape
A landscape is the visible features of an area of land, its landforms, and how they integrate with natural or human-made features, often considered in terms of their aesthetic appeal.''New Oxford American Dictionary''. A landscape includes th ...
,
limnology,
hydrology
Hydrology () is the scientific study of the movement, distribution, and management of water on Earth and other planets, including the water cycle, water resources, and drainage basin sustainability. A practitioner of hydrology is called a hydro ...
,
ecosystem
An ecosystem (or ecological system) is a system formed by Organism, organisms in interaction with their Biophysical environment, environment. The Biotic material, biotic and abiotic components are linked together through nutrient cycles and en ...
s and
climate
Climate is the long-term weather pattern in a region, typically averaged over 30 years. More rigorously, it is the mean and variability of meteorological variables over a time spanning from months to millions of years. Some of the meteoro ...
.
The effects of human activities on Earth can be seen, for example, in regards to
biodiversity loss
Biodiversity loss happens when plant or animal species disappear completely from Earth (extinction) or when there is a decrease or disappearance of species in a specific area. Biodiversity loss means that there is a reduction in Biodiversity, b ...
, and
climate change
Present-day climate change includes both global warming—the ongoing increase in Global surface temperature, global average temperature—and its wider effects on Earth's climate system. Climate variability and change, Climate change in ...
. Various start dates for the Anthropocene have been proposed, ranging from the beginning of the
Neolithic Revolution
The Neolithic Revolution, also known as the First Agricultural Revolution, was the wide-scale transition of many human cultures during the Neolithic period in Afro-Eurasia from a lifestyle of hunter-gatherer, hunting and gathering to one of a ...
(12,000–15,000 years ago), to as recently as the 1960s. The biologist
Eugene F. Stoermer is credited with first coining and using the term ''anthropocene'' informally in the 1980s;
Paul J. Crutzen re-invented and popularized the term.
The
Anthropocene Working Group (AWG) of the Subcommission on Quaternary Stratigraphy (SQS) of the ICS voted in April 2016 to proceed towards a formal
golden spike (GSSP) proposal to define an Anthropocene epoch in the
geologic time scale
The geologic time scale or geological time scale (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the process of relating strata to time) and geochro ...
. The group presented the proposal to the
International Geological Congress in August 2016.
In May 2019, the AWG voted in favour of submitting a formal proposal to the ICS by 2021.
The proposal located potential
stratigraphic
Stratigraphy is a branch of geology concerned with the study of rock layers (strata) and layering (stratification). It is primarily used in the study of sedimentary and layered volcanic rocks.
Stratigraphy has three related subfields: lithost ...
markers to the mid-20th century.
This time period coincides with the start of the
Great Acceleration, a post-
World War II
World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...
time period during which global
population growth
Population growth is the increase in the number of people in a population or dispersed group. The World population, global population has grown from 1 billion in 1800 to 8.2 billion in 2025. Actual global human population growth amounts to aroun ...
,
pollution
Pollution is the introduction of contaminants into the natural environment that cause harm. Pollution can take the form of any substance (solid, liquid, or gas) or energy (such as radioactivity, heat, sound, or light). Pollutants, the component ...
and
exploitation of natural resources
The exploitation of natural resources describes using natural resources, often non-renewable or limited, for economic growth or development. Environmental degradation, human insecurity, and social conflict frequently accompany natural resource ex ...
have all increased at a dramatic rate. The
Atomic Age also started around the mid-20th century, when the risks of
nuclear war
Nuclear warfare, also known as atomic warfare, is a War, military conflict or prepared Policy, political strategy that deploys nuclear weaponry. Nuclear weapons are Weapon of mass destruction, weapons of mass destruction; in contrast to conven ...
s,
nuclear terrorism, and
nuclear accident
A nuclear and radiation accident is defined by the International Atomic Energy Agency (IAEA) as "an event that has led to significant consequences to people, the environment or the facility." Examples include radiation poisoning, lethal effect ...
s increased.
Twelve candidate sites were selected for the GSSP; the sediments of
Crawford Lake, Canada were finally proposed, in July 2023, to mark the lower boundary of the Anthropocene, starting with the Crawfordian stage/age in 1950.
In March 2024, after 15 years of deliberation, the Anthropocene Epoch proposal of the AWG was voted down by a wide margin by the SQS, owing largely to its shallow sedimentary record and extremely recent proposed start date.
The ICS and the IUGS later formally confirmed, by a near unanimous vote, the rejection of the AWG's Anthropocene Epoch proposal for inclusion in the Geologic Time Scale.
[The Anthropocene: IUGS-ICS Statement. March 20, 2024. https://www.iugs.org/_files/ugd/f1fc07_ebe2e2b94c35491c8efe570cd2c5a1bf.pdf] The IUGS statement on the rejection concluded: "Despite its rejection as a formal unit of the Geologic Time Scale, Anthropocene will nevertheless continue to be used not only by Earth and
environmental scientists, but also by social scientists, politicians and economists, as well as by the public at large. It will remain an invaluable descriptor of human impact on the Earth system."
Development of the concept
An early concept for the Anthropocene was the
Noosphere by
Vladimir Vernadsky
Vladimir Ivanovich Vernadsky (), also spelt Volodymyr Ivanovych Vernadsky (; – 6 January 1945), was a Russian, Ukrainian, and Soviet mineralogist and geochemist who is considered one of the founders of geochemistry, biogeochemistry, and radio ...
, who in 1938 wrote of "scientific thought as a geological force". Scientists in the
Soviet Union
The Union of Soviet Socialist Republics. (USSR), commonly known as the Soviet Union, was a List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 until Dissolution of the Soviet ...
appear to have used the term ''Anthropocene'' as early as the 1960s to refer to the
Quaternary
The Quaternary ( ) is the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy (ICS), as well as the current and most recent of the twelve periods of the ...
, the most recent
geological period
The geologic time scale or geological time scale (GTS) is a representation of time based on the geologic record, rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the process of relating stratum, strata ...
.
Ecologist
Eugene F. Stoermer subsequently used ''Anthropocene'' with a different sense in the 1980s and the term was widely popularised in 2000 by
atmospheric chemist Paul J. Crutzen,
who regarded the influence of human behavior on Earth's atmosphere in recent centuries as so significant as to constitute a new geological epoch.
The term ''Anthropocene'' is informally used in scientific contexts. The
Geological Society of America entitled its 2011 annual meeting: ''
Archean
The Archean ( , also spelled Archaean or Archæan), in older sources sometimes called the Archaeozoic, is the second of the four geologic eons of Earth's history of Earth, history, preceded by the Hadean Eon and followed by the Proterozoic and t ...
to Anthropocene: The past is the key to the future''. The new epoch has no agreed start-date, but one proposal, based on atmospheric evidence, is to fix the start with the
Industrial Revolution
The Industrial Revolution, sometimes divided into the First Industrial Revolution and Second Industrial Revolution, was a transitional period of the global economy toward more widespread, efficient and stable manufacturing processes, succee ...
1780, with the invention of the
steam engine
A steam engine is a heat engine that performs Work (physics), mechanical work using steam as its working fluid. The steam engine uses the force produced by steam pressure to push a piston back and forth inside a Cylinder (locomotive), cyl ...
.
Other scientists link the new term to earlier events, such as the rise of agriculture and the
Neolithic Revolution
The Neolithic Revolution, also known as the First Agricultural Revolution, was the wide-scale transition of many human cultures during the Neolithic period in Afro-Eurasia from a lifestyle of hunter-gatherer, hunting and gathering to one of a ...
(around 12,000 years
BP).
Evidence of relative human impact – such as the
growing human influence on land use, ecosystems,
biodiversity
Biodiversity is the variability of life, life on Earth. It can be measured on various levels. There is for example genetic variability, species diversity, ecosystem diversity and Phylogenetics, phylogenetic diversity. Diversity is not distribut ...
, and
species extinction – is substantial; scientists think that human impact has significantly changed (or halted) the growth of biodiversity.
Those arguing for earlier dates posit that the proposed Anthropocene may have begun as early as 14,000–15,000 years
BP, based on geologic evidence; this has led other scientists to suggest that "the onset of the Anthropocene should be extended back many thousand years"; this would make the Anthropocene essentially synonymous with the current term, ''
Holocene
The Holocene () is the current geologic time scale, geological epoch, beginning approximately 11,700 years ago. It follows the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene to ...
''.
Anthropocene Working Group
In 2008, the Stratigraphy Commission of the
Geological Society of London
The Geological Society of London, known commonly as the Geological Society, is a learned society based in the United Kingdom. It is the oldest national geological society in the world and the largest in Europe, with more than 12,000 Fellows.
Fe ...
considered a proposal to make the Anthropocene a formal unit of geological epoch divisions.
A majority of the commission decided the proposal had merit and should be examined further. Independent working groups of scientists from various geological societies began to determine whether the Anthropocene will be formally accepted into the
Geological Time Scale.

In January 2015, 26 of the 38 members of the International Anthropocene Working Group published a paper suggesting the
Trinity test on 16 July 1945 as the starting point of the proposed new epoch.
However, a significant minority supported one of several alternative dates.
A March 2015 report suggested either 1610 or 1964 as the beginning of the Anthropocene. Other scholars pointed to the
diachronous character of the physical strata of the Anthropocene, arguing that onset and impact are spread out over time, not reducible to a single instant or date of start.
A January 2016 report on the climatic, biological, and geochemical signatures of human activity in sediments and ice cores suggested the era since the mid-20th century should be recognised as a
geological epoch distinct from the Holocene.
The Anthropocene Working Group met in April 2016 to consolidate evidence supporting the argument for the ''Anthropocene'' as a true geologic epoch. Evidence was evaluated and the group voted to recommend ''Anthropocene'' as the new geological epoch in August 2016.
In April 2019, the
Anthropocene Working Group (AWG) announced that they would vote on a formal proposal to the
International Commission on Stratigraphy
The International Commission on Stratigraphy (ICS), sometimes unofficially referred to as the International Stratigraphic Commission, is a daughter or major subcommittee grade scientific organization that concerns itself with stratigraphy, strati ...
, to continue the process started at the 2016 meeting.
In May 2019, 29 members of the 34 person AWG panel voted in favour of an official proposal to be made by 2021. The AWG also voted with 29 votes in favour of a starting date in the mid 20th century. Ten candidate sites for a
Global boundary Stratotype Section and Point
A Global Boundary Stratotype Section and Point (GSSP), sometimes referred to as a golden spike, is an internationally agreed upon reference point on a stratigraphic section which defines the lower boundary of a stage on the geologic time scale. ...
have been identified, one of which will be chosen to be included in the final proposal.
Possible markers include
microplastics
Microplastics are "synthetic solid particles or polymeric matrices, with regular or irregular shape and with size ranging from 1 μm to 5 mm, of either primary or secondary manufacturing origin, which are insoluble in water." Microplastics a ...
,
heavy metals
upright=1.2, Crystals of lead.html" ;"title="osmium, a heavy metal nearly twice as dense as lead">osmium, a heavy metal nearly twice as dense as lead
Heavy metals is a controversial and ambiguous term for metallic elements with relatively h ...
, or radioactive nuclei left by tests from
thermonuclear weapons.
In November 2021, an alternative proposal that the Anthropocene is a
geological event, not an epoch, was published and later expanded in 2022. This challenged the assumption underlying the case for the Anthropocene epoch – the idea that it is possible to accurately assign a precise date of start to highly
diachronous processes of human-influenced Earth system change. The argument indicated that finding a single
GSSP
A Global Boundary Stratotype Section and Point (GSSP), sometimes referred to as a golden spike, is an internationally agreed upon reference point on a stratigraphic section which defines the lower boundary of a stage on the geologic time scale. ...
would be impractical, given human-induced changes in the Earth system occurred at different periods, in different places, and spread under different rates. Under this model, the Anthropocene would have many events marking human-induced impacts on the planet, including the
mass extinction of large vertebrates, the
development of early farming, land clearance in the Americas, global-scale industrial transformation during the
Industrial Revolution
The Industrial Revolution, sometimes divided into the First Industrial Revolution and Second Industrial Revolution, was a transitional period of the global economy toward more widespread, efficient and stable manufacturing processes, succee ...
, and the start of the
Atomic Age. The authors are members of the AWG who had voted against the official proposal of a starting date in the mid-20th century, and sought to reconcile some of the previous models (including
Ruddiman and
Maslin proposals). They cited
Crutzen's original concept, arguing that the Anthropocene is much better and more usefully conceived of as an unfolding geological event, like other major transformations in Earth's history such as the
Great Oxidation Event
The Great Oxidation Event (GOE) or Great Oxygenation Event, also called the Oxygen Catastrophe, Oxygen Revolution, Oxygen Crisis or Oxygen Holocaust, was a time interval during the Earth's Paleoproterozoic era when the Earth's atmosphere an ...
.
In July 2023, the AWG chose
Crawford Lake in
Ontario, Canada
Ontario is the southernmost Provinces and territories of Canada, province of Canada. Located in Central Canada, Ontario is the Population of Canada by province and territory, country's most populous province. As of the 2021 Canadian census, it ...
as a site representing the beginning of the proposed new epoch. The sediment in that lake shows a spike in levels of plutonium from hydrogen bomb tests, a key marker the group chose to place the start of the Anthropocene in the 1950s, along with other elevated markers including carbon particles and nitrates from the burning of
fossil fuels
A fossil fuel is a flammable carbon compound- or hydrocarbon-containing material formed naturally in the Earth's crust from the buried remains of prehistoric organisms (animals, plants or microplanktons), a process that occurs within geologica ...
and widespread application of chemical fertilizers respectively. Had it been approved, the official declaration of the new Anthropocene epoch would have taken place in August 2024, and its first
age
Age or AGE may refer to:
Time and its effects
* Age, the amount of time someone has been alive or something has existed
** East Asian age reckoning, an Asian system of marking age starting at 1
* Ageing or aging, the process of becoming older
...
may have been named Crawfordian after the lake.
Rejection in 2024 vote by IUGS
In March 2024, an internal vote was held by the
IUGS
The International Union of Geological Sciences (IUGS) is an international non-governmental organization devoted to global cooperation in the field of geology. As of 2023, it represents more than 1 million geoscientists around the world.
About
Fo ...
: After nearly 15 years of debate, the proposal to ratify the Anthropocene had been defeated by a 12-to-4 margin, with 2 abstentions.
These results were not out of a dismissal of human impact on the planet, but rather an inability to constrain the Anthropocene in a geological context. This is because the widely-adopted 1950 start date was found to be prone to recency bias. It also overshadowed earlier examples of human impacts, many of which happened in different parts of the world at different times. Although the proposal could be raised again, this would require the entire process of debate to start from the beginning.
The results of the vote were officially confirmed by the IUGS and upheld as definitive later that month.
Proposed starting point
Industrial Revolution
Crutzen proposed the Industrial Revolution as the start of Anthropocene.
Lovelock proposes that the Anthropocene began with the first application of the
Newcomen steam engine
The atmospheric engine was invented by Thomas Newcomen in 1712, and is sometimes referred to as the Newcomen fire engine (see below) or Newcomen engine. The engine was operated by condensing steam being drawn into the cylinder, thereby creating ...
in 1712. The
Intergovernmental Panel on Climate Change
The Intergovernmental Panel on Climate Change (IPCC) is an intergovernmental body of the United Nations. Its job is to "provide governments at all levels with scientific information that they can use to develop climate policies". The World Met ...
takes the pre-industrial era (chosen as the year 1750) as the baseline related to changes in long-lived, well mixed greenhouse gases. Although it is apparent that the Industrial Revolution ushered in an unprecedented global human impact on the planet, much of Earth's landscape already had been profoundly modified by human activities. The human impact on Earth has grown progressively, with few substantial slowdowns. A 2024 scientific perspective paper authored by a group of scientists led by
William J. Ripple proposed the start of the Anthropocene around 1850, stating it is a "compelling choice ... from a population, fossil fuel, greenhouse gasses, temperature, and land use perspective."
Mid 20th century (Great Acceleration)
In May 2019 the twenty-nine members of the Anthropocene Working Group (AWG) proposed a start date for the Epoch in the mid-20th century, as that period saw "a rapidly rising human population accelerated the pace of industrial production, the use of
agricultural chemicals and other human activities. At the same time, the first atomic-bomb blasts littered the globe with radioactive debris that became embedded in sediments and glacial ice, becoming part of the geologic record." The official start-dates, according to the panel, would coincide with either the radionuclides released into the atmosphere from bomb detonations in 1945, or with the
Limited Nuclear Test Ban Treaty of 1963.
First atomic bomb (1945)
The peak in
radionuclide
A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is a nuclide that has excess numbers of either neutrons or protons, giving it excess nuclear energy, and making it unstable. This excess energy can be used in one of three ...
s fallout consequential to atomic bomb testing during the 1950s is another possible date for the beginning of the Anthropocene (the detonation of the
first atomic bomb in 1945 or the
Partial Nuclear Test Ban Treaty in 1963).
Etymology
The name ''Anthropocene'' is a combination of ''
anthropo-'' from the
Ancient Greek
Ancient Greek (, ; ) includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Greek ...
() meaning 'human' and ''
-cene'' from () meaning 'new' or 'recent'.
As early as 1873, the Italian geologist
Antonio Stoppani acknowledged the increasing power and effect of humanity on the Earth's systems and referred to an 'anthropozoic era'.
Nature of human effects
Biodiversity loss
The human impact on biodiversity forms one of the primary attributes of the Anthropocene. Humankind has entered what is sometimes called the Earth's sixth major extinction. Most experts agree that human activities have accelerated the rate of species extinction.
The exact rate remains controversial – perhaps 100 to 1000 times the normal background rate of extinction.
Anthropogenic extinctions started as humans migrated out of Africa over 60,000 years ago. Increases in global rates of extinction have been elevated above background rates since at least 1500, and appear to have accelerated in the 19th century and further since.
Rapid
economic growth
In economics, economic growth is an increase in the quantity and quality of the economic goods and Service (economics), services that a society Production (economics), produces. It can be measured as the increase in the inflation-adjusted Outp ...
is considered a primary driver of the contemporary displacement and eradication of other species.
According to the 2021 ''Economics of Biodiversity'' review, written by
Partha Dasgupta and published by the UK government, "biodiversity is declining faster than at any time in human history." A 2022 scientific review published in ''Biological Reviews'' confirms that an anthropogenic
sixth mass extinction event is currently underway. A 2022 study published in ''
Frontiers in Ecology and the Environment'', which surveyed more than 3,000 experts, states that the extinction crisis could be worse than previously thought, and estimates that roughly 30% of species "have been globally threatened or driven extinct since the year 1500." According to a 2023 study published in ''Biological Reviews'' some 48% of 70,000 monitored species are experiencing population declines from human activity, whereas only 3% have increasing populations.
Biogeography and nocturnality
Studies of
urban evolution give an indication of how species may respond to stressors such as temperature change and toxicity. Species display varying abilities to respond to altered environments through both
phenotypic plasticity and genetic
evolution
Evolution is the change in the heritable Phenotypic trait, characteristics of biological populations over successive generations. It occurs when evolutionary processes such as natural selection and genetic drift act on genetic variation, re ...
. Researchers have documented the movement of many species into regions formerly too cold for them, often at rates faster than initially expected.
Permanent changes in the distribution of organisms from human influence will become identifiable in the
geologic record. This has occurred in part as a result of changing climate, but also in response to farming and fishing, and to the accidental introduction of non-native species to new areas through global travel.
The ecosystem of the entire
Black Sea
The Black Sea is a marginal sea, marginal Mediterranean sea (oceanography), mediterranean sea lying between Europe and Asia, east of the Balkans, south of the East European Plain, west of the Caucasus, and north of Anatolia. It is bound ...
may have changed during the last 2000 years as a result of nutrient and silica input from eroding deforested lands along the
Danube River
The Danube ( ; see also other names) is the second-longest river in Europe, after the Volga in Russia. It flows through Central and Southeastern Europe, from the Black Forest south into the Black Sea. A large and historically important riv ...
.
Researchers have found that the growth of the human population and expansion of human activity has resulted in many species of animals that are normally active during the day, such as elephants, tigers and boars, becoming nocturnal to avoid contact with humans, who are largely diurnal.
Climate change
One geological symptom resulting from human activity is increasing
atmospheric carbon dioxide () content. This signal in the Earth's climate system is especially significant because it is occurring much faster, and to a greater extent, than previously. Most of this increase is due to the
combustion
Combustion, or burning, is a high-temperature exothermic redox chemical reaction between a fuel (the reductant) and an oxidant, usually atmospheric oxygen, that produces oxidized, often gaseous products, in a mixture termed as smoke. Combustion ...
of
fossil fuel
A fossil fuel is a flammable carbon compound- or hydrocarbon-containing material formed naturally in the Earth's crust from the buried remains of prehistoric organisms (animals, plants or microplanktons), a process that occurs within geolog ...
s such as coal,
oil, and
gas.
Geomorphology
Changes in drainage patterns traceable to human activity will persist over geologic time in large parts of the continents where the geologic regime is erosional. This involves, for example, the paths of roads and highways defined by their grading and drainage control. Direct changes to the form of the Earth's surface by human activities (
quarry
A quarry is a type of open-pit mining, open-pit mine in which dimension stone, rock (geology), rock, construction aggregate, riprap, sand, gravel, or slate is excavated from the ground. The operation of quarries is regulated in some juri ...
ing and
landscaping
Landscaping refers to any activity that modifies the visible features of an area of land, including the following:
# Living elements, such as flora or fauna; or what is commonly called gardening, the art and craft of growing plants with a goal ...
, for example) also record human impacts.
It has been suggested that the deposition of
calthemite
Calthemite is a secondary deposit, derived from concrete, Lime (material), lime, Mortar (masonry), mortar or other calcareous material outside the cave environment.Smith, G.K. (2016). "Calcite straw stalactites growing from concrete structures" ...
formations exemplify a natural process which has not previously occurred prior to the human modification of the Earth's surface, and which therefore represents a unique process of the Anthropocene. Calthemite is a secondary deposit, derived from concrete,
lime,
mortar or other calcareous material ''outside the cave environment''.
Calthemite
Calthemite is a secondary deposit, derived from concrete, Lime (material), lime, Mortar (masonry), mortar or other calcareous material outside the cave environment.Smith, G.K. (2016). "Calcite straw stalactites growing from concrete structures" ...
s grow on or under man-made structures (including mines and tunnels) and mimic the shapes and forms of cave
speleothem
A speleothem (; ) is a geological formation made by mineral deposits that accumulate over time in natural caves. Speleothems most commonly form in calcareous caves due to carbonate dissolution reactions. They can take a variety of forms, depen ...
s, such as
stalactite
A stalactite (, ; , ) is a mineral formation that hangs from the ceiling of caves, hot springs, or man-made structures such as bridges and mines. Any material that is soluble and that can be deposited as a colloid, or is in suspension (chemistry ...
s,
stalagmite
A stalagmite (, ; ; )
is a type of rock formation that rises from the floor of a cave due to the accumulation of material deposited on the floor from ceiling drippings. Stalagmites are typically composed of calcium carbonate, but may consist ...
s, flowstone ''etc''.
Stratigraphy
Sedimentological record
Human activities, including deforestation and road construction, are believed to have elevated average total sediment fluxes across the Earth's surface.
However, construction of dams on many rivers around the world means the rates of sediment deposition in any given place do not always appear to increase in the Anthropocene. For instance, many
river delta
A river delta is a landform, archetypically triangular, created by the deposition of the sediments that are carried by the waters of a river, where the river merges with a body of slow-moving water or with a body of stagnant water. The creat ...
s around the world are actually currently starved of sediment by such dams, and are subsiding and failing to keep up with sea level rise, rather than growing.
Fossil record
Increases in erosion due to farming and other operations will be reflected by changes in sediment composition and increases in deposition rates elsewhere. In land areas with a depositional regime, engineered structures will tend to be buried and preserved, along with litter and debris. Litter and debris thrown from boats or carried by rivers and creeks will accumulate in the marine environment, particularly in coastal areas, but also in mid-ocean
garbage patches. Such human-created artifacts preserved in stratigraphy are known as ''
technofossils''.

Changes in biodiversity will also be reflected in the fossil record, as will species introductions. An example cited is the domestic chicken, originally the
red junglefowl
The red junglefowl (''Gallus gallus''), also known as the Indian red junglefowl (and formerly the bankiva or bankiva-fowl), is a species
A species () is often defined as the largest group of organisms in which any two individuals of the a ...
''Gallus gallus'', native to south-east Asia but has since become the world's most common bird through human breeding and consumption, with over 60 billion consumed annually and whose bones would become fossilised in landfill sites. Hence, landfills are important resources to find "technofossils".
Trace elements
In terms of trace elements, there are a range of distinct signatures left by modern societies. For example, in the
Upper Fremont Glacier in Wyoming, there is a layer of
chlorine
Chlorine is a chemical element; it has Symbol (chemistry), symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between ...
present in ice cores from 1960's atomic weapon testing programs, as well as a layer of
mercury associated with coal plants in the 1980s.
From the late 1940s, nuclear tests have led to local
nuclear fallout
Nuclear fallout is residual radioactive material that is created by the reactions producing a nuclear explosion. It is initially present in the mushroom cloud, radioactive cloud created by the explosion, and "falls out" of the cloud as it is ...
and severe contamination of test sites both on land and in the surrounding marine environment. Some of the
radionuclide
A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is a nuclide that has excess numbers of either neutrons or protons, giving it excess nuclear energy, and making it unstable. This excess energy can be used in one of three ...
s that were released during the tests are
Cs,
Sr,
Pu,
Pu,
Am, and
I. These have been found to have had significant impact on the environment and on human beings. In particular,
Cs and
Sr have been found to have been released into the marine environment and led to
bioaccumulation
Bioaccumulation is the gradual accumulation of substances, such as pesticides or other chemicals, in an organism. Bioaccumulation occurs when an organism absorbs a substance faster than it can be lost or eliminated by catabolism and excretion. T ...
over a period through
food chain
A food chain is a linear network of links in a food web, often starting with an autotroph (such as grass or algae), also called a producer, and typically ending at an apex predator (such as grizzly bears or killer whales), detritivore (such as ...
cycles. The carbon isotope
C, commonly released during nuclear tests, has also been found to be integrated into the atmospheric
CO, and infiltrating the
biosphere
The biosphere (), also called the ecosphere (), is the worldwide sum of all ecosystems. It can also be termed the zone of life on the Earth. The biosphere (which is technically a spherical shell) is virtually a closed system with regard to mat ...
, through
ocean-atmosphere gas exchange. Increase in
thyroid cancer
Thyroid cancer is cancer that develops from the tissues of the thyroid gland. It is a disease in which cells grow abnormally and have the potential to spread to other parts of the body. Symptoms can include swelling or a lump in the neck, ...
rates around the world is also surmised to be correlated with increasing proportions of the
I radionuclide.
The highest global concentration of radionuclides was estimated to have been in 1965, one of the dates which has been proposed as a possible benchmark for the start of the formally defined Anthropocene.
Human burning of
fossil fuel
A fossil fuel is a flammable carbon compound- or hydrocarbon-containing material formed naturally in the Earth's crust from the buried remains of prehistoric organisms (animals, plants or microplanktons), a process that occurs within geolog ...
s has also left distinctly elevated concentrations of black carbon, inorganic ash, and spherical carbonaceous particles in recent sediments across the world. Concentrations of these components increases markedly and almost simultaneously around the world beginning around 1950.
Anthropocene markers
A marker that accounts for a substantial global impact of humans on the total environment, comparable in scale to those associated with significant perturbations of the geological past, is needed in place of minor changes in atmosphere composition. A range of markers characterizing the period have been identified, such as
silicone
In Organosilicon chemistry, organosilicon and polymer chemistry, a silicone or polysiloxane is a polymer composed of repeating units of siloxane (, where R = Organyl group, organic group). They are typically colorless oils or elastomer, rubber ...
or
aluminium
Aluminium (or aluminum in North American English) is a chemical element; it has chemical symbol, symbol Al and atomic number 13. It has a density lower than that of other common metals, about one-third that of steel. Aluminium has ...
, but most prominently
plastic
Plastics are a wide range of synthetic polymers, synthetic or Semisynthesis, semisynthetic materials composed primarily of Polymer, polymers. Their defining characteristic, Plasticity (physics), plasticity, allows them to be Injection moulding ...
, with plastic, reminiscent of archaeological ages like the
iron age
The Iron Age () is the final epoch of the three historical Metal Ages, after the Chalcolithic and Bronze Age. It has also been considered as the final age of the three-age division starting with prehistory (before recorded history) and progre ...
, marking an archaeological plastic age or the anthropocene even as a geological plastic epoch.
A useful candidate for holding markers in the geologic time record is the
pedosphere
The pedosphere () is the Earth's crust, outermost layer of the Earth that is composed of soil and subject to soil formation processes. It exists at the interface of the lithosphere, Atmosphere of Earth, atmosphere, hydrosphere and biosphere. The ...
. Soils retain information about their climatic and geochemical history with features lasting for centuries or millennia. Human activity is now firmly established as the sixth factor of soil formation. Humanity affects pedogenesis directly by, for example, land levelling, trenching and embankment building, landscape-scale
control of fire by early humans
The control of fire by early humans was a critical technology enabling the evolution of humans. Fire provided a source of warmth and lighting, protection from predators (especially at night), a way to create more advanced hunting tools, and ...
, organic matter enrichment from additions of manure or other waste, organic matter impoverishment due to continued cultivation and compaction from
overgrazing
Overgrazing occurs when plants are exposed to intensive grazing for extended periods of time, or without sufficient recovery periods. It can be caused by either livestock in poorly managed agricultural applications, game reserves, or nature ...
. Human activity also affects pedogenesis indirectly by drift of eroded materials or pollutants. Anthropogenic soils are those markedly affected by human activities, such as repeated ploughing, the addition of fertilisers, contamination, sealing, or enrichment with artefacts (in the
World Reference Base for Soil Resources they are classified as
Anthrosols and
Technosols). An example from archaeology would be
dark earth phenomena when long-term human habitation enriches the soil with
black carbon
Black carbon (BC) is the light-absorbing refractory form of Chemical_element, elemental carbon remaining after pyrolysis (e.g., charcoal) or produced by incomplete combustion (e.g., soot).
Tihomir Novakov originated the term black carbon in ...
.
Anthropogenic soils are recalcitrant repositories of artefacts and properties that testify to the dominance of the human impact, and hence appear to be reliable markers for the Anthropocene. Some anthropogenic soils may be viewed as the 'golden spikes' of geologists (
Global Boundary Stratotype Section and Point
A Global Boundary Stratotype Section and Point (GSSP), sometimes referred to as a golden spike, is an internationally agreed upon reference point on a stratigraphic section which defines the lower boundary of a stage on the geologic time scale. ...
), which are locations where there are strata successions with clear evidences of a worldwide event, including the appearance of distinctive fossils. Drilling for fossil fuels has also created holes and tubes which are expected to be detectable for millions of years. The astrobiologist
David Grinspoon has proposed that the site of the Apollo 11 Lunar landing, with the disturbances and artifacts that are so uniquely characteristic of our species' technological activity and which will survive over geological time spans could be considered as the 'golden spike' of the Anthropocene.
An October 2020 study coordinated by
University of Colorado at Boulder
The University of Colorado Boulder (CU Boulder, CU, or Colorado) is a Public university, public research university in Boulder, Colorado, United States. Founded in 1876, five months before Colorado became a Federated state, state, it is the fla ...
found that distinct physical, chemical and biological changes to Earth's rock layers began around the year 1950. The research revealed that since about 1950, humans have doubled the amount of
fixed nitrogen on the planet through industrial production for agriculture, created a
hole in the ozone layer through the industrial scale release of
chlorofluorocarbon
Chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) are fully or partly Halogenation, halogenated hydrocarbons that contain carbon (C), hydrogen (H), chlorine (Cl), and fluorine (F). They are produced as volatility (chemistry), volat ...
s (CFCs), released enough
greenhouse gas
Greenhouse gases (GHGs) are the gases in the atmosphere that raise the surface temperature of planets such as the Earth. Unlike other gases, greenhouse gases absorb the radiations that a planet emits, resulting in the greenhouse effect. T ...
ses from fossil fuels to cause planetary level
climate change
Present-day climate change includes both global warming—the ongoing increase in Global surface temperature, global average temperature—and its wider effects on Earth's climate system. Climate variability and change, Climate change in ...
, created tens of thousands of
synthetic mineral-like compounds that do not naturally occur on Earth, and caused almost one-fifth of
river sediment worldwide to no longer reach the ocean due to dams, reservoirs and diversions. Humans have produced so many millions of tons of plastic each year since the early 1950s that
microplastics
Microplastics are "synthetic solid particles or polymeric matrices, with regular or irregular shape and with size ranging from 1 μm to 5 mm, of either primary or secondary manufacturing origin, which are insoluble in water." Microplastics a ...
are "forming a near-ubiquitous and unambiguous marker of Anthropocene".
The study highlights a strong correlation between global human population size and growth, global productivity and global energy use and that the "extraordinary outburst of consumption and productivity demonstrates how the Earth System has departed from its Holocene state since c. 1950 CE, forcing abrupt physical, chemical and biological changes to the Earth's stratigraphic record that can be used to justify the proposal for naming a new epoch—the Anthropocene."
A December 2020 study published in ''
Nature
Nature is an inherent character or constitution, particularly of the Ecosphere (planetary), ecosphere or the universe as a whole. In this general sense nature refers to the Scientific law, laws, elements and phenomenon, phenomena of the physic ...
'' found that the total anthropogenic mass, or human-made materials, outweighs all the
biomass
Biomass is a term used in several contexts: in the context of ecology it means living organisms, and in the context of bioenergy it means matter from recently living (but now dead) organisms. In the latter context, there are variations in how ...
on earth, and highlighted that "this quantification of the human enterprise gives a mass-based quantitative and symbolic characterization of the human-induced epoch of the Anthropocene."
Debates

Although the validity of ''Anthropocene'' as a scientific term remains disputed, its underlying premise, i.e., that humans have become a geological force, or rather, the dominant force shaping the Earth's climate, has found traction among academics and the public. In an opinion piece for ''
Philosophical Transactions of the Royal Society B'',
Rodolfo Dirzo, Gerardo Ceballos, and
Paul R. Ehrlich write that the term is "increasingly penetrating the lexicon of not only the academic socio-sphere, but also society more generally", and is now included as an entry in the
Oxford English Dictionary
The ''Oxford English Dictionary'' (''OED'') is the principal historical dictionary of the English language, published by Oxford University Press (OUP), a University of Oxford publishing house. The dictionary, which published its first editio ...
. The University of Cambridge, as another example, offers a degree in Anthropocene Studies. In the public sphere, the term ''Anthropocene'' has become increasingly ubiquitous in activist, pundit, and political discourses. Some who are critical of the term ''Anthropocene'' nevertheless concede that "For all its problems,
tcarries power." The popularity and currency of the word has led scholars to label the term a "charismatic meta-category" or "charismatic mega-concept." The term, regardless, has been subject to a variety of criticisms from social scientists, philosophers, Indigenous scholars, and others.
The anthropologist John Hartigan has argued that due to its status as a charismatic meta-category, the term ''Anthropocene'' marginalizes competing, but less visible, concepts such as that of "multispecies." The more salient charge is that the ready acceptance of ''Anthropocene'' is due to its conceptual proximity to the status quo – that is, to notions of human individuality and centrality.
Other scholars appreciate the way in which the term ''Anthropocene'' recognizes humanity as a geological force, but take issue with the indiscriminate way in which it does. Not all humans are equally responsible for the climate crisis. To that end, scholars such as the feminist theorist
Donna Haraway and sociologist
Jason Moore, have suggested naming the Epoch instead as the ''
Capitalocene''. Such implies
capitalism
Capitalism is an economic system based on the private ownership of the means of production and their use for the purpose of obtaining profit. This socioeconomic system has developed historically through several stages and is defined by ...
as the fundamental reason for the ecological crisis, rather than just humans in general. However, according to philosopher
Steven Best, humans have created "hierarchical and growth-addicted societies" and have demonstrated "ecocidal proclivities" long before the emergence of capitalism. Hartigan, Bould, and Haraway all critique what ''Anthropocene'' does as a term; however, Hartigan and Bould differ from Haraway in that they criticize the utility or validity of a geological framing of the climate crisis, whereas Haraway embraces it.
In addition to "Capitalocene," other terms have also been proposed by scholars to trace the roots of the Epoch to causes other than the human species broadly. Janae Davis, for example, has suggested the "Plantationocene" as a more appropriate term to call attention to the role that
plantation
Plantations are farms specializing in cash crops, usually mainly planting a single crop, with perhaps ancillary areas for vegetables for eating and so on. Plantations, centered on a plantation house, grow crops including cotton, cannabis, tob ...
agriculture has played in the formation of the Epoch, alongside Kathryn Yusoff's argument that racism as a whole is foundational to the Epoch. The Plantationocene concept traces "the ways that plantation logics organize modern economies, environments, bodies, and social relations." In a similar vein, Indigenous studies scholars such as Métis geographer
Zoe Todd have argued that the Epoch must be dated back to the colonization of the Americas, as this "names the problem of colonialism as responsible for contemporary environmental crisis." Potawatomi philosopher Kyle Powys Whyte has further argued that the Anthropocene has been apparent to Indigenous peoples in the Americas since the inception of colonialism because of "colonialism's role in environmental change."
Other critiques of ''Anthropocene'' have focused on the genealogy of the concept. Todd also provides a
phenomenological account, which draws on the work of the philosopher
Sara Ahmed, writing: "When discourses and responses to the Anthropocene are being generated within institutions and disciplines which are embedded in broader systems that act as de facto 'white public space,' the academy and its power dynamics must be challenged." Other aspects which constitute current understandings of the concept of the ''Anthropocene'' such as the ontological split between nature and society, the assumption of the centrality and individuality of the human, and the framing of environmental discourse in largely scientific terms have been criticized by scholars as concepts rooted in colonialism and which reinforce systems of postcolonial domination. To that end, Todd makes the case that the concept of ''Anthropocene'' must be indigenized and
decolonized if it is to become a vehicle of justice as opposed to white thought and domination.
Eco-philosopher David Abram, in a book chapter titled 'Interbreathing in the Humilocene', has proposed adoption of the term ‘Humilocene’ (the Epoch of Humility), which emphasizes an ethical imperative and ecocultural direction that human societies should take. The term plays with the etymological roots of the term ‘human’, thus connecting it back with terms such as humility, humus (the soil), and even a corrective sense of humiliation that some human societies should feel given their collective destructive impact on the earth.
"Early anthropocene" model
William Ruddiman has argued that the Anthropocene began approximately 8,000 years ago with the
development of farming and sedentary cultures.
At that point, humans were dispersed across all continents except
Antarctica
Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean (also known as the Antarctic Ocean), it contains the geographic South Pole. ...
, and the
Neolithic Revolution
The Neolithic Revolution, also known as the First Agricultural Revolution, was the wide-scale transition of many human cultures during the Neolithic period in Afro-Eurasia from a lifestyle of hunter-gatherer, hunting and gathering to one of a ...
was ongoing. During this period, humans developed agriculture and
animal husbandry
Animal husbandry is the branch of agriculture concerned with animals that are raised for meat, animal fiber, fibre, milk, or other products. It includes day-to-day care, management, production, nutrition, selective breeding, and the raising ...
to supplement or replace
hunter-gatherer
A hunter-gatherer or forager is a human living in a community, or according to an ancestrally derived Lifestyle, lifestyle, in which most or all food is obtained by foraging, that is, by gathering food from local naturally occurring sources, esp ...
subsistence. Such innovations were followed by a wave of
extinction
Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...
s, beginning with large
mammal
A mammal () is a vertebrate animal of the Class (biology), class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three ...
s and terrestrial birds. This wave was driven by both the direct activity of humans (e.g. hunting) and the indirect consequences of
land-use change for agriculture. Landscape-scale
burning
Combustion, or burning, is a high-temperature exothermic redox chemical reaction between a fuel (the reductant) and an oxidant, usually atmospheric oxygen, that produces oxidized, often gaseous products, in a mixture termed as smoke. Combust ...
by prehistoric hunter-gathers may have been an additional early source of anthropogenic atmospheric carbon. Ruddiman also claims that the greenhouse gas emissions in-part responsible for the Anthropocene began 8,000 years ago when ancient farmers cleared forests to grow crops.
Ruddiman's work has been challenged with data from an earlier interglaciation ("Stage 11", approximately 400,000 years ago) which suggests that 16,000 more years must elapse before the current Holocene interglaciation comes to an end, and thus the early anthropogenic hypothesis is invalid. Also, the argument that "something" is needed to explain the differences in the Holocene is challenged by more recent research showing that all interglacials are different.
Homogenocene
Homogenocene (from old Greek:
homo-, ''same'';
geno-, ''kind''; kainos-, ''new'';) is a more specific term used to define our current epoch, in which
biodiversity
Biodiversity is the variability of life, life on Earth. It can be measured on various levels. There is for example genetic variability, species diversity, ecosystem diversity and Phylogenetics, phylogenetic diversity. Diversity is not distribut ...
is diminishing and
biogeography
Biogeography is the study of the species distribution, distribution of species and ecosystems in geography, geographic space and through evolutionary history of life, geological time. Organisms and biological community (ecology), communities o ...
and
ecosystems
An ecosystem (or ecological system) is a system formed by Organism, organisms in interaction with their Biophysical environment, environment. The Biotic material, biotic and abiotic components are linked together through nutrient cycles and en ...
around the globe seem more and more similar to one another mainly due to
invasive species
An invasive species is an introduced species that harms its new environment. Invasive species adversely affect habitats and bioregions, causing ecological, environmental, and/or economic damage. The term can also be used for native spec ...
that have been introduced around the globe either on purpose (crops, livestock) or inadvertently. This is due to the newfound globalism that humans participate in, as species traveling across the world to another region was not as easily possible in any point of time in history as it is today.
The term Homogenocene was first used by Michael Samways in his editorial article in the ''Journal of Insect Conservation'' from 1999 titled "Translocating fauna to foreign lands: Here comes the Homogenocene."
The term was used again by John L. Curnutt in the year 2000 in ''Ecology'', in a short list titled "A Guide to the Homogenocene", which reviewed ''Alien species in North America and Hawaii: impacts on natural ecosystems'' by George Cox.
Charles C. Mann, in his acclaimed book ''
1493: Uncovering the New World Columbus Created'', gives a bird's-eye view of the mechanisms and ongoing implications of the homogenocene.
Society and culture
Humanities
The concept of the Anthropocene has also been approached via humanities such as philosophy, literature and art. In the scholarly world, it has been the subject of increasing attention through special journals, conferences, and disciplinary reports. The Anthropocene, its attendant timescale, and ecological implications prompt questions about death and the end of civilisation, memory and archives, the scope and methods of humanistic inquiry, and emotional responses to the "end of nature". Some scholars have posited that the realities of the Anthropocene, including "human-induced biodiversity loss, exponential increases in per-capita resource consumption, and global
climate change
Present-day climate change includes both global warming—the ongoing increase in Global surface temperature, global average temperature—and its wider effects on Earth's climate system. Climate variability and change, Climate change in ...
," have made the goal of environmental
sustainability
Sustainability is a social goal for people to co-exist on Earth over a long period of time. Definitions of this term are disputed and have varied with literature, context, and time. Sustainability usually has three dimensions (or pillars): env ...
largely unattainable and obsolete.
Historians have actively engaged the Anthropocene. In 2000, the same year that Paul Crutzen coined the term, world historian John McNeill published ''Something New Under the Sun'',
tracing the rise of human societies' unprecedented impact on the planet in the twentieth century.
In 2001, historian of science
Naomi Oreskes revealed the systematic efforts to undermine trust in
climate change
Present-day climate change includes both global warming—the ongoing increase in Global surface temperature, global average temperature—and its wider effects on Earth's climate system. Climate variability and change, Climate change in ...
science and went on to detail the corporate interests delaying action on the environmental challenge. Both McNeill and Oreskes became members of the Anthropocene Working Group because of their work correlating human activities and planetary transformation.
Popular culture
* In 2019, the English musician
Nick Mulvey released a music video on YouTube named "In the Anthropocene". In cooperation with Sharp's Brewery, the song was recorded on 105 vinyl records made of washed-up plastic from the Cornish coast.
* ''
The Anthropocene Reviewed'' is a podcast and book by author
John Green
John Michael Green (born August 24, 1977) is an American author and YouTuber. His books have more than 50 million copies in print worldwide, including ''The Fault in Our Stars'' (2012), which is one of the List of best-selling books#Bet ...
, where he "reviews different facets of the human-centered planet on a five-star scale".
* Photographer
Edward Burtynsky created "The Anthropocene Project" with Jennifer Baichwal and Nicholas de Pencier, which is a collection of photographs, exhibitions, a film, and a book. His photographs focus on landscape photography that captures the effects human beings have had on the earth.
* In 2015, the American
death metal
Death metal is an extreme metal, extreme subgenre of heavy metal music. It typically employs heavily distorted and low-tuned guitars, played with techniques such as palm muting and tremolo picking; deep death growl, growling vocals; aggressive ...
band
Cattle Decapitation released its seventh studio album titled ''
The Anthropocene Extinction''.
* In 2020, Canadian musician
Grimes
Claire Elise Boucher (; born March 17, 1988), known professionally as Grimes, is a Canadian musician, singer, songwriter, and record producer. Her lyrics often touch on science fiction and feminist themes. The visuals in her videos are elabora ...
released her fifth studio album titled ''
Miss Anthropocene''. The name is also a pun on the feminine title "Miss" and the words "
misanthrope
Misanthropy is the general hatred, dislike, or distrust of the Human, human species, human behavior, or human nature. A misanthrope or misanthropist is someone who holds such views or feelings. Misanthropy involves a negative evaluative attitu ...
" and "Anthropocene."
See also
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References
External links
The Anthropocene epoch: have we entered a new phase of planetary history? ''The Guardian'', 2019
Drawing A Line In The Mud: Scientists Debate When 'Age Of Humans' Began NPR. 17 March 2021.
* (lecture given by Professor Will Steffen in Melbourne, Australia)
8 billion humans: How population growth and climate change are connected as the 'Anthropocene engine' transforms the planet ''
The Conversation''. 3 November 2022.
{{Authority control
Holocene
Human impact on the environment
Human ecology
1960s neologisms
Events in the geological history of Earth