What is the Anthropocene?

I started out writing a blog called ‘What is the Capitalocene?’ [INSERT LINK HERE], to help disseminate a paper that I wrote, and recently had accepted for publication, called ‘Education and Full Employment in the Capitalocene‘. However, I decided to split off the science-based part of the blog here, so as to keep the length more manageable.

Recently I was discussing the ecological crisis (e.g. biodiversity decline, climate change, etc.) with a senior class, and asked them what they thought was the cause of the problem. A girl in the back called out:


This answer is precisely the view taken by the Anthropocene.

The Anthropocene refers to the geological time period dominated by humans. As in ‘anthropo’, meaning humans, and ‘-ocene’, the geological suffix denoting a series/epoch on the International Chronostratigraphic Chart, which is a timeline of earth’s history that geologists have created using fossil and other physical evidence. If you’ve never seen the Chart before, it’s worth studying for a moment. You can see that it’s divided into five categories in descending lengths of time: eonothem/eons, erathem/eras, system/periods, series/epochs, and stage/ages. If you are new to this like I was, these dual divisions of time would not have immediately made an impression on you, but for the underpinning science, they’re important.

The first of these each of those time divisions (e.g. eonothem, erathem, system, series, and stage) derive from chronostratigraphy, which is the science of determining the relative ages and relations of rock strata, and are the basis of the boundaries between types of rock (see GSSPs below). The second of the time divisions (e.g. eon, era, period, epoch, age) derive from geochronology, which is the science of dating the time sequence of events in earth’s history; they do not define boundaries between rocks and they are subject to refinement and recalibration. These two branches of geology are related and work together. For more in-depth reading that helped me understand their importance, see Zalasiewicz et al.’s (2013) Chronostratigraphy and geochronology, and for an excellent history of their development, see Finney and Edwards’ (2016) The “Anthropocene” epoch: Scientific decision or political statement?

At the time of writing, as you can see the Anthropocene does not appear on the Chart. But there is an Anthropocene Working Group tasked with developing the concept, and which has decided to treat it as a formal unit on the Chart defined by a “golden spike”, the informal term for a Global Boundary Stratotype Section and Point (GSSP). These GSSPs, or golden spikes, define the beginning of a stage on the Chart, and the International Commission on Stratigraphy has published Rules on the criteria that must and should be fulfilled for a GSSP. For most (but not all) of the four broad columns on the Chart, if you look at the right-most part, you can see a little icon that looks like a spike, representing a GSSP. In many cases the “golden spike” is not a mere metaphor; geologists will mark a GSSP by driving a marker into the rock that marks the precise boundary between the stages, though the marker need not be made of gold. The photo shown in this Wikipedia entry marks the beginning of the Ediacaran period, the oldest GSSP marker at the time of writing.

Now, a question which arose pretty quickly for me was, Why do some GSSPs only mark the beginning of a stage, whereas others also mark the beginning of a new series, system, etc.? This seemed important as the Anthropocene concept is by definition being developed at the series level, rather than stage, system, erathem, or eonothem. In other words, the new proposed time division is the AnthropOCENE, not AnthropIAN (for a stage), nor AnthropOGENE (for a system), etc. But why?

In trying to answer this question, I started looking more carefully at the different divisions on the Chart. The first thing I noticed was that there are only two eonothems / eons: the Precambrian and the Phanerozoic. These are separated by the Fortunian GSSP, the beginning of what is often called the Cambrian explosion, after which all the major animal phyla start appearing in the fossil record. So this was a major event in earth’s history, enough to mark the beginning of a new time division. Why this occurred at this time is an interesting question in itself, but beyond the scope of this blog and I leave it to you to investigate for yourself.

Of the next major time divisions, the erathems / eras, I was particularly interested in the Danian event, since it marks the beginning of the most recent erathem / era, the Cenozoic, and a mass extinction event. After reading the paper defining the Danian GSSP, I understood that this was defined by the asteroid impact that wiped out the non-avian dinosaurs about 66 million years ago, but I still didn’t have an answer to my question: What criteria are used to define the beginning of a new series, system, erathem, etc.? After all, as mentioned above, there are clear rules about what criteria must and should be met to define a new stage. At this point, I thought it was time to ask some experts, and as I so often have done, sent an email to a few leading geologists with my question. I got superb replies, greatly advancing my understanding (including pointing out the distinction between chronostratigraphy and geochronology that I mentioned above).

Basically, what they said was that there are no rigid rules defining the beginning of a new series, system, etc., that the science is an interpretative process, and changes in such classifications occur with new evidence, theoretical development, and advance in understanding generally, in line with what one would expect from science. They also attached some papers, two of which I hyperlinked above, which I read and that helped advance my understanding significantly.

To bring the discussion to bear on why the Anthropocene is being developed at the series level, rather than any other, the current series, the Holocene, is defined by the recession of the last ice age, and the evidence suggests that human activity is causing a departure from the natural conditions that would lead to the end of this relatively warm period, and the beginning of the next glacial episode; namely, from anthropogenic climate change. However, as just suggested above, in time, this view could change, and the Anthropocene might need to be ‘upgraded’ to the Anthropogene if the science determines that human activity has now caused a departure from the current Quaternary system altogether, defined by cycles of extension and recession of glaciers. With regard to the possibility of human activity being the cause of a new erathem / era – the Anthropozoic – I suppose the evidence would have to suggest the beginning of a mass extinction event, for which there is growing evidence.

However, to link all of this back to my original purpose, to explain the importance of the Capitalocene, because of the way the Anthropocene has been defined, it cannot remain an exclusively geological concept; the concept is inherently political too. This is the argument persuasively made by Finney and Edwards’ (2016) The “Anthropocene” epoch: Scientific decision or political statement?. To return to the point which the student expressed in the introductory story, who exactly is responsible for all of this ecological degradation (e.g. biodiversity loss, climate change, etc.)? The Anthropocene only offers ‘humans’ as an answer. There is no distinction made amongst humans, which is clearly problematic since there is a vast disparity between rich and poor in their ecological impact. This is the distinction I want to explore in my blog post on the Capitalocene.