Figure 1. Main prehistoric and historical features considered
as potential starting points and stratigraphic markers for the onset of
the ‘Anthropocene Epoch’, compared with the continuous increasing trend
of the ‘Anthropocenne Event’. The current AWG proposal is highlighted in
green. Pleistocene and Holocene time scales (blue) are in thousand years
before present (kyr BP) and last-centuries scale is in calendar years
(CE).
This proposal was not without internal and external controversy. The
main points of debate included the diachronic nature of human
disturbance across the globe, hindering the identification of a single
date for the beginning of the Anthropocene, and the argument that a mere
75 years could not represent a geological epoch, which typically spans
tens of thousands to millions of years (Edwards, 2015; Finney &
Edwards, 2015; Ellis et al., 2016). Additionally, concerns were raised
about the vulnerability of the GSSP, consisting of only 10-15 cm of
unconsolidated lake sediment, to removal by erosion or environmental
changes such as lake drying. The AWG did not consider the diachronism in
human disturbance across the planet, as this would have threatened its
primary objective, which was to define a globally synchronous
chronostratigraphic unit. The AWG was also reluctant to consider other
possibilities, notably the ’early Anthropocene’ as defined by Ruddiman
(2003, 2013), which attributes mid-Holocene atmospheric greenhouse gas
increases to large-scale deforestation and farming (CO2;
8-7 kyr BP) and rice cultivation in SE Asia (CH4; 6-5
kyr BP). These omissions resulted in internal conflicts and led to the
resignation of some AWG members.
As the AWG was finalizing its proposal for submission to the SQS, a
group of stratigraphers, including relevant members of the ICS and the
IUGS, suggested a different proposal based on the spatiotemporal
variability of human impact on Earth. They argued that the Anthropocene
was better defined as a geological event (Gibbard et al., 2022a, b).
Geological events are characterized by their time-transgressive and
multi-temporal nature, ranging from seconds to millions of years and
from local to global scales. Such events do not require GSSPs or
formalization and can cause significant disruptions in the Earth System.
For instance, the Paleoproterozoic Great Oxidation Event (GOE), which
lasted 4 billion years (2.4-2.0 Ga), fundamentally altered life on Earth
by introducing an aerobic atmosphere. Other notable events include the
Great Ordovician Biodiversity Event (GOBE; 485-455 Ma) and the
Middle-Late Devonian forestation of continents (DeFE; 390-360 Ma).
In October 2023, the AWG finally submitted its Anthropocene proposal to
the SQS, including the aforementioned GSSP (Lake Crawford),
stratigraphic markers (radionuclides, fly ashes, etc.), and starting
point (1952 CE) (Waters et al., 2024). Four months later, the proposal
was rejected by the SQS with 12 votes against (66%, more than the 60%
required), 4 in favor, and 2 abstentions. Consequently, progress toward
approval by the ICS Executive and ratification by the IUGS was halted,
and the case was considered closed by most SQS members. However, the AWG
is currently seeking to declare the voting null due to procedural
irregularities (Voosen, 2024; Witze, 2024). Finally, in March 2024, the
rejection was ratified by the IUGS Executive (IUGS, 2024).
It is evident that the focus of scrutiny lies not in the magnitude of
anthropogenic disturbance on the Earth System, widely accepted as fact,
but rather on the specific proposal put forth by the AWG. Therefore,
there is also the possibility of submitting another proposal. However,
opponents argue that the outcome of the initial vote suggests that any
subsequent proposal would likely face similar rejection (Gibbard, pers.
comm.).
The difficulty of finding a globally synchronous starting point to
define a formal series/epoch has led to reinforced support for the idea
of the Anthropocene as an event, considered the most suitable term to
encompass the full range of anthropogenic cultural and environmental
effects (Walker et al., 2023). The only drawback is terminological. The
termination ‘-cene’ was initially chosen by Crutzen & Stoermer (2000)
because it is reserved for epochs of the Cenozoic Era (i.e., Paleocene,
Eocene, Oligocene, Miocene, Pliocene, Pleistocene, Holocene). Therefore,
referring to the Anthropocene as a geological event could be misleading
and terminologically incorrect (Head et al., 2023).
Several years ago, I proposed the term ‘Humanized Earth System’ (HES), a
name devoid of chronostratigraphic meaning, to describe the new physical
and functional state of the planet under global human influence (Rull,
2016). By using the term ’Earth System’ instead of simply ’Earth,’ it
underscores that human impact has extended beyond local and regional
scales to affect the components of the Earth System (i.e., atmosphere,
hydrosphere, lithosphere, biosphere, cryosphere) and their global
interactions. This perspective has been consistently emphasized by the
AWG in its publications (e.g., Zalasiewicz et al., 2019). Employing this
concept, the recently proposed ’Anthropocene Event’ could be more
accurately termed the ’Earth-System Humanization Event’ (ESHE), aligning
with the current terminology for other events such as the aforementioned
GOE, GOBE, DeFE, and others.
The term ‘humanized’ is preferred over the prefix ‘anthropo-‘ because
the latter simply refers to the human condition (from the Greek
‘anthropos’ meaning ‘human’), while the former emphasizes the impact of
humans on the Earth System. The prefix ‘anthropo-‘ had already been used
in the late 18th century by Stoppani (1873) to define the prospective
‘Anthropozoic Era’, characterized by the occurrence of human fossils and
objects linked to human presence. This author did not consider modern
human ancestors such as Australopithecus and the extinctHomo species – he was a priest and, as such, did not believe in
evolution – and was unable to date the beginning of this purported
human era. Modern evolutionary knowledge and the use of current dating
methods showed that Stoppani’s ‘Anthropozoic’ coincided almost perfectly
with the current Quaternary Period, initiated approximately 2.6 million
years ago (Rull, 2021). However, human influence on the Earth System,
which is what the ’Anthropocene’ concept – regardless of whether it
refers to an epoch or an event – wants to emphasize, is much more
recent and restricted to the last tens of thousands of years, at most
(Lewis & Maslin, 2015).
In summary, if we must consider the human influence on the Earth System
as a geological event, as defined by Gibbard et al. (2022a, b) and
Walker et al. (2023), then the term ’Earth-System Humanization Event’
(ESHE) – or alternatively the ‘Humanized Earth System Event’ (HESE) –
appears more appropriate than the ’Anthropocene Event’ from both
terminological and conceptual points of view. In this context, the
prefix ‘anthropo-‘ could be used to designate Stoppani’s ‘Anthropozoic
Era’, which is based on qualitative (presence/absence) evidence, whereas
the ESHE could be viewed as a quantitative feature, in terms of the
intensity of human impact. If this were the case, then the ‘Anthropozoic
Era’ would follow the Cenozoic, which would have ended with the
appearance of the first remains of modern humans or hominins (Rull,
2021).