Human or Earth history?

When you think of the Anthropocene, what comes to mind? Do you envisage fossil fuel power stations, industrialisation, exponentially growing human populations, atomic bombs, globalisation and economic expansion? Or, do you picture the human-induced changes to Earth's atmosphere, sedimentary layers, and stratigraphic composition?

If you thought more along the lines of the first description, it may be that you (probably unintentionally) perceive the Anthropocene more as a unit of human history than Earth history. We humans have historically divided blocks of time into different named periods, making communication and analysis easier (Edwards 2015). Take for example the Victorian era, precisely defined by the reign of England's Queen Victoria (1837-1901) (Edwards 2015). Human divided time periods can also be based on stages of cultural development, such as the Bronze Age, which does not have a specific start and end date as it depends on the place and specific civilisation's development (Edwards 2015). Contrastingly, the Geologic Time Scale relates to stratigraphic rock records, correlating to chronostratigraphic units of time. Does this informality make the Victorian era or Bronze Age any less important in human development? No. But it does make them units of human history, and not Earth history.

The Anthropocene: a unit of human history, or Earth history? (Source)

Crucially, we must also decide if the Anthropocene is a recently historic unit of time, or if it is instead an idea for a future unit of time (Finney 2014). The ICS, who create and decide on units for the International Chronostratigraphic Chart (ICC), do not postulate for the future, they assess the stratigraphic record which exists today. Some arguments within the Anthropocene discourse often follow a line of "Oh, but future geologists will look back in millions of years and see chemicals, plastics and atomic fallout in the strata"...have we forgotten that the ICS does NOT consider what might make future Earth History? That is not the way it works. There is no predefined geologic record for the future. If the Anthropocene will be more significant in the future, then that is when it should be classified and formally ratified. Having said that, is the Anthropocene such a profound concept that the unit of time should no longer conform to traditional, predefined time spans and standards as set out in the ICS Stratigraphic Guide?

As Finney (2014) has argued, human-induced impacts on Earth Systems are just starting to be recorded in sediments, but we cannot be sure that a significant and unique sedimentary signal will assemble. Can we really justify a profound change in the ICC and GTS, one which could end our current Holocene interglacial epoch, based upon potential projections and hypothesising of what the future might show us, considering there currently seems to be a lack of consensus based on the past? Finney (2014) also raises an interesting point (once which I had not considered until now), that our precise human observations and measurements are those that would be used for studying human-induced impacts, as opposed to looking in stratigraphic records for information. The stratigraphy for the Anthropocene looks pretty bare in comparison to the multitude of events which humans have observed and recorded over recent history (Finney 2014). 

Finally, I must address the elephant in the room when it comes to the whole concept of the Anthropocene. Are we being a little anthropocentric, assigning an interval of Earth History to our human existence on the planet? Why must we hastily define the Anthropocene as a formal unit of geological history, when its use may be just as powerful to the global population as an informal term? I believe that recognising that we are in the "Anthropocene" (whatever that may mean to you) could go one of two ways. It will either be a huge wake up call, alerting politicians and the general public to our detrimental effects on the planet, OR, it will be an anthropocentric comfort, a pat on the back, knowing that humanity is just that powerful and a dominant God-like species. The AWG must address whether the Anthropocene concept has stemmed from an anthropocentric perspective, rather than purely a geologic and scientific one, and if it belongs as a truly significant era of human history as opposed to one of Earth history. 

A human concept, lost in stratigraphy?

"As stratigraphers, we require criteria to map the Anthropocene with relevant and consistent meaning. Presently, we are left to map a unit conceptually rather than conceptualizing a mappable stratigraphic unit."

The above quote (emphasis added), written by Autin and Holbrook (2012) in an article in GSA Today, forced me to question some fundamental arguments in this debate. Is the Anthropocene a term rooted in pop culture, based more on conceptual meaning in search of a stratigraphic signal, as opposed to starting with a distinct stratigraphic record? Finney (2014) asked the very same question, and I find his opinion akin to mine. The more I become involved with the Anthropocene debate in this blogging journey, the more I am questioning everything I once believed at face-value without a second thought. The idea behind this post is rather like the famous question of what came first, the chicken or the egg? In this instance, should concept come before stratigraphic evidence?

A defining feature of the Anthropocene, distinct from other units of geologic time, is that the proposed epoch is in the present and continually evolving. Therefore, instead of looking back in retrospect at fossils and stratigraphic evidence, the conceptualising step must come first, with stratigraphic evidence following later. Whether this is the 'correct' way to classify a new unit of geologic time is dubious. Historically, changes in stratigraphy have been identified, and then conceptual units of time have been assigned to these clear shifts and events in the strata. In our present day, the world has identified a new concept, one which views humanity as a centrally dominant geologic force, and now we're searching for a stratigraphic signal to fit that concept. Perhaps this signifies a time for change in how the Geologic Time Scale (GTS) should be constructed in a present-day mindset, recognising that fossils and stratigraphic evidence can become secondary to conceptual assignments. 

Finney (2014) continues this philosophical debate by questioning the conceptual basis of the GTS, asking whether it is suitable to be applied to 'chronometers of recorded and future human history'. As so much of what constitutes the Anthropocene is in the present and near-future, should it formally become part of the GTS, considering that all units currently recognised are events which occurred deep in the past (Finney 2014)? I agree with Finney that this is a very important question that needs addressing by the AWG, but I do not agree that the Anthropocene (or any other future time intervals) should be written off from formalisation just because it has not occurred in the deep past. In my eyes, the GTS should modernise to accommodate for new periods of time which will likely come to fruition during humanity's existence on the planet. This may be as simple as providing alternative time resolution intervals which acknowledge shorter events and ages (e.g. centuries to millennia) within larger chronostratigraphic units (e.g. epochs and periods). Clearly the time resolution currently used on the GTS (millions to billions of years) would scarcely recognise the Anthropocene, a blip of time in Earth's 4.5 billion year history. So, should the GTS downscale to additionally accommodate smaller, yet important, intervals of time, extending the use of GSSAs? Or, should the GTS refuse to formalise these smaller events and continue formalising only those longer time intervals with robust GSSPs and a clear stratigraphic record?

Crucially, the Anthropocene is the first proposed geologic interval whereby the focus itself (humanity) is able to influence and change the very nature of the time wished to classify. This brings me onto my next big question to address: is the Anthropocene a unit of human history rather than Earth history?