Figure 1. ‘Metropolis Globe New York’ by Werner Kunz, distributed under a Creative Commons licence from http://www.flickr.com/photos/werkunz/3545012600/
This paper briefly summarises recent discussions of the anthropocene by geologists, biochemists, climatologists, and other scientists. It goes on to argue that archaeologists should engage with these issues too.

‘A geological age of our own making’
The anthropocene is a term coined by atmospheric chemist Paul Crutzen, best known for his work on ozone depletion. It denotes an unfolding epoch in the earth’s environmental history, characterised by human transformation of its ecological systems which tip the planet into a new geological era (Crutzen and Stoermer 2000). The idea of the anthropocene is based on recognition of the impact of human activity on what was formerly thought to be the ‘natural’ world, and indeed the realisation that atmospheric and other geophysical systems are now inextricably entangled with cultural systems. As Revkin put it a decade earlier (though his term the anthrocene never quite stuck) “we are entering… a geological age of our own making” (Revkin 1992).
There is no widespread agreement about when the anthropocene began. Crutzen and Stoermer favour the start of the industrial period in the late 18th century, the time of the invention of the steam engine and the onset of a period of huge growth in world population and expansion of cities, with corresponding exploitation of mineral, agricultural, water and other resources. Subsequent developments include proliferation of coal-burning factories, extensive damming of rivers, modification of terrain, invention of the motor engine and the use of oil and gas on a massive scale. Numerous effects can be cited: atmospheric and oceanic pollution, climate change, melting ice caps, changes in sea-levels, shifts in patterns of soil erosion and sedimentation, extinction of species, species-migrations, and so on (Crutzen 2009, Revkin 2002, Zalasiewicz et al 2010). Perhaps the most cited indicator is a rapid rise in global concentrations of CO2 and methane (as measured in air trapped in polar ice).
A group of geologists from the Stratigraphy Commission of the Geological Society of London (Zalasiewisicz et al 2008) support Crutzen and Stoermer’s view about where in time the boundary should be placed, while acknowledging that the positioning of it is somewhat arbitrary. They point out the additional usefulness of the global spread of radioactive isotopes, resulting from atomic bomb tests in the latter half of the 20th century, as geological markers for the proposed new epoch.
The palaeoclimatologist William Ruddiman, on the other hand, argues that the start of the anthropocene should be taken back to the beginning of the Neolithic period. Forest clearance by humans created an increase of carbon dioxide in the atmosphere from 8000 years ago, while cultivation and irrigation techniques led to a huge rise in methane levels about 5000 years ago, with profound consequences for climatic patterns (Ruddiman 2003, 2005).
Others have stated that the anthropocene goes back much further than that. A recent article in Nature presents evidence for human hunting practices in the late Pleistocene leading to the extinction of American megafauna, bringing about a radical decrease in methane emissions. The conclusion drawn from the study is that “the onset of the ‘Anthropocene’ should be recalibrated to 13,400 years before present, coincident with the first large-scale migrations of humans into the Americas” (Smith et al 2010).
Some archaeological perspectives
Archaeology can clearly be of use in providing the evidence upon which the chronological boundary for the start of the anthropocene can be based. Yet in a sense the attempt to place the boundary too precisely in time may be a mistake. Boundaries between geological periods are best viewed from the perspective of tens of thousands, hundreds of thousands or even millions of years in the future. From such a perspective, a few thousand years either way will make little difference. It is virtually impossible to fix such a boundary to the nearest century, especially when the evidence is viewed from the situated perspective of someone living inside the geological era itself, while its distinct deposits are still forming. A geologist of the far future may well take human artefacts – any artefact (from flint handaxe to potsherd to rocket grenade) – as type-fossils for the anthropocene epoch, with no greater degree of precision required. In this sense (and perhaps in other senses too) the painted cave of Lascaux may turn out to be just as true an indicator of the anthropocene as dumps of radioactive waste from nuclear power plants.
For many investigators, the anthropocene is defined mainly in terms of its scientific indicators, not so much in terms of the processes which gave rise to such indicators. There is circularity in such arguments. Thus Steffen et al (2007), dating the start of the epoch to the Industrial Revolution when C02 levels start to rise, argue that all the technological development and human-nature interaction prior to the Industrial Revolution belonged to a pre-anthropocene phase. This practice of dating the start of the anthropocene only to the moments when its effects can be measured – even when it is clear that underlying processes have been in operation for some time beforehand – entails a lack of engagement with the long history and prehistory of human transformation of environments.
There is a corresponding assumption that the anthropocene can only ever be defined on a planetary scale (that is, when human activity starts to impact on global environmental systems). Yet the term should also refer to smaller and more local interactions between persons and things that are partly constitutive of changes on the larger scale. By this I mean more than just past embodied interactions (use of hand-held tool s to shape materials) and human-landscape interactions that archaeologists are so familiar with. The many other scales on which peoples and materials interact, through the use of technologies that extend the range of perception and action far beyond the reach of the body itself, are relevant here (Edgeworth 2010). Modern technology enables people to act remotely upon the atomic and molecular structure of matter on the scale of nanometers, for example. Indeed, it is precisely transactions on micro and nano scales – the construction of smaller and faster micro-processors, the use of nano-devices to shape nano-materials, the manipulation of DNA in genetic engineering, etc – that are now speeding up effects of human action on the much larger scale of planetary systems – paradoxically and simultaneously providing possible means to reverse some of those very effects. Today, the anthropocene exists just as surely inside the particle accelerator at Cerne, or at the nanotube cantilever tip of an atomic force microscope, as it does in global patterns of atmospheric or oceanic change.
It works the other way too. Despite attempts to set ‘planetary boundaries’ or safe limits for human impact on natural systems (Biello 2009), the Anthropocene has already extended beyond the Earth and into the solar system. If it is a geological era, it is interplanetary in extent. The hundreds of satellites orbiting the Earth are just as much artefacts of the Anthropocene as dams, oil wells, mobile phones, microprocessors and other kinds of human engineering. The term should therefore cover orbital space, other planets and astronomical bodies as well as Earth. Geologists or archaeologists of the far future may find its type fossils (human artefacts) on Mars and the moon as well as on our home planet: indeed these materials, in the form of spacecraft and experimental apparatus and scientific detritus, have already started to be deposited in those places (Gorman 2005a, 2005b, Zalasiewicz 2008). There has been an interchange of geological material. Over 2000 moon rocks weighing in total more than 800 pounds have been brought back to Earth by Apollo missions and unmanned Soviet Luna spacecraft, and the geology of Mars has likewise been disturbed by excavation of samples by robotic devices, operated remotely from Earth.
Archaeologists work primarily with medium scale manifestations of the anthropocene. Traces in the ground of quarries, mines, canals, irrigation channels, moats, wells, roads, defensive earthworks, industrial residues, artificial ponds, river embankments, field boundaries, working surfaces, pits, postholes, boundary ditches, occupation layers, cultivation soils, and so on, are the stuff of archaeology. Taken individually, these would not be counted as evidence. Taken together, they actually amount to a geological signal of major transformations of the terrestrial surfaces of the Earth on a global scale.
As Richard Periman puts it, “The Anthropocene begins to emerge when we consider human-environmental activity at a local level, compounded by thousands of years, affecting vast areas of interlocking landscapes” (Periman 2006: 562 – see Periman’s article for detailed discussion of how people have interacted with, altered and created landscapes through time, with extensive references to relevant archaeological work). A problem, however, is that evidence presented falls outside of the more or less arbitrary chronological boundary for the supposed start of the new geological epoch. An inadvertent effect of placing the start of the anthropocene in the late 18th century is to exclude archaeological perspectives, evidence and insights regarding the preceding period from the ongoing debate. Periman puts it more bluntly: “by defining the Anthropocene as a geological epoch beginning only 200 years ago, Crutzen and Stoermer truncate thousands of years of human interactions with the global environment” (Periman 2006, 558).
Artificial ground
Geologists do recognise and take note of ‘artificial ground’ as a stratigraphic indicator of the anthropocene, but tend to regard it as a feature of the industrial and modern periods only. Urban archaeologists can attest, however, that the artificial ground of many industrial cities did not suddenly begin accumulating in the late 18th century. If the anthropogenic deposits that comprise the artificial ground of London, Rome, Mexico City, Novgorod, Istanbul, Beijing and many other major cities were taken as a primary geological signal, the anthropocene (dated from its first traces in the stratigraphic record) would be understood to start much earlier.

Figure 2. Recording the ‘artificial ground’ on an urban site in Winchester. Photo by Wessex Archaeology http://www.flickr.com/photos/wessexarchaeology/sets/72157612474555574/. (Creative Commons licence).
Figure 2 shows new development taking place above the material traces of a succession of collapsed floor layers tipping into a large medieval pit, which may itself overlie traces of the Saxon and Roman cities, and possibly earlier Iron Age occupation too. At Winchester, as in many other urban centres, several metres of artificial ground have already built up prior to the onset of the industrial period.
Likewise, Near Eastern tell sites such as Çatalhöyük and Jericho provide examples of massive build-ups of anthropogenic materials from prehistoric periods, going right back to the early Neolithic.
Artificial ground only started to be mapped by geologists in the last thirty years or so, with classifications of different types of evidence within it being fairly rudimentary (Rosenbaum et al 2003). It is mostly not considered to be ‘real’ geology. Yet archaeologists have been making detailed studies of it for much longer, building up a coherent set of methods to deal with its complexities. Specific practical and interpretive skills exist for finding soil horizons which mark the first phase of human activity on a given site, as well as for exploring the interleaving of natural and cultural deposits/processes. As geologists increasingly come to focus on the artificial ground as an indicator of the anthropocene, this archaeological expertise might come in useful.
Natural ground
The designation of artificial ground presupposes the existence of its opposite – natural ground. But in the case of Holocene deposits, many investigators (with notable exceptions such as William Ruddiman) have underestimated the extent to which the forces that have moulded the terrestrial surfaces of the earth have been intermeshed with cultural agencies. This applies not only to urbanisation, but also for example to rivers and floodplains once thought to have been almost wholly shaped by natural processes. Some standard geomorphological models of river erosion and sedimentation were based on studies of rivers that – far from being natural as assumed – had been subject to extensive human modification in the past (Walter and Merritts 2008, see also Montgomery 2008).
The sheer extent of past human involvement in the shaping of river and floodplain morphology is not fully realised. It is true that the 20th century proliferation of huge dams such as the Grand Coulee, the largest concrete structure in the United States, have helped to turn rivers like the Columbia into ‘organic machines’ (White 1995). Such dams, and the artificial lakes they create, are often cited as features of the anthropocene. But these are themselves the outcome of long developmental processes in the technologies of river modification. There is abundant evidence of dams built for irrigation in ancient civilisations of Egypt, Sumeria and Mesopotamia – or for milling in medieval Europe – causing great changes in patterns of erosion and sedimentation, specifically in the creation of soils effectively impounded by dams. Humans and their artefacts have been intervening in the ‘natural’ water cycle for thousands of years: indeed there is a sense in which most rivers can themselves be regarded as material artefacts (see online article on that subject here).
Archaeologists can help to fill in these blind spots in the scientific vision of the anthropocene.
Conclusion
The anthropocene is different from other geological periods in that the very science that seeks to understand it is part of the phenomena under investigation, as well as a key component of any attempt to redress imbalances and resolve problems identified. Yet the methods of the natural sciences, based on principles of detached observation, are ill-equipped on their own to cope with the complex loops of reflexivity and multiple feedback involved. Insights gained from anthropology, archaeology, sociology, history, cultural theory, material culture studies, and social study of science and technology need to be incorporated into scientific forms of analysis. “The challenge before us”, as Kotchen and Young (2007, 149) argue, is “to develop a science of coupled human–biophysical systems”. That means developing ways of thinking that cut right across disciplinary boundaries, extending scientific vocabularies to encompass the full range of intermeshed cultural-natural configurations of anthropocene evidence.
In its complex reflexivities, its multiple feedback loops, its interplanetary extent, and its inextricable entanglement of nature and culture, the anthropocene is a geological epoch like no other. The difficult task of understanding it should not be left entirely to biochemists, geologists, climatologists and other natural scientists. Archaeologists should grapple with the anthropocene too…..
References
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