I was recently asked to reply to the following discussion prompt: “Discuss the merits of a ‘new’ geological epoch, the Anthropocene. What value does it provide and how can archaeologists contribute towards its definition?”
Here is my reply:
Earlier this year, the Subcommission on Quaternary Stratigraphy (part of the International Commission on Stratigraphy, which in turn is part of the International Union of Geological Sciences) announced the ratification of the division of our current Epoch (the Holocene) into the following three Ages:
Greenlandian – 11,700 to 8,236 years before 2000 CE (b2k)
Northgrippian – 8,236 to 4,250 years b2k
Meghalayan – 4250 years b2k to the present
The start of the Meghalayan is marked by a so-called “Golden Spike,” or, more specifically, a Global Boundary Stratotype Section and Point (GSSP). As can be seen on the International Chronostratigraphic Chart above, GSSPs are used to define most Eon, Era, Period, Epoch, and Age boundaries. The specific GSSP associated with the beginning of the Meghalayan is the onset of a two-century global drought event which, for those familiar with Ancient Egypt, roughly coincides with the First Intermediate Period.
This dramatic change in global climate left evidence on all seven continents simultaneously; the geological requirement for a Golden Spike. What is most interesting about the Meghalayan GSSP is that it is the first one to be associated with a “global cultural event…sparked by a global climatic event.” Not only did Egypt experience a Dark Age between the Old and Middle Kingdoms – Mesopotamia saw the fall of Akkad and the Indus Valley Civilization went into decline.
Outside of the work done to subdivide the Holocene, the Working Group on the ‘Anthropocene’ was convened under the auspices of the Subcommission on Quaternary Stratigraphy in 2009. The name ‘Anthropocene’ was popularized in 2000 by Nobel Laureate chemist Paul Crutzen to highlight man’s impact on the Earth. Unlike the Holocene (and Meghalayan), defining the ‘Anthropocene’ as a geological epoch is a matter of “political relevance” and has no scientific merit.
A geologically-defined stratigraphic boundary must be globally discernible. A well-known example of this is the K-Pg Boundary associated with the end of the Cretaceous. With respect to human impacts on the planet, different proposed markers (such as anthropogenic extinctions, mining, agriculture, irrigation, and industrial pollutants) entered the record at different times throughout the world. When the search for an ‘Anthropocene’ Golden Spike is narrowed to global phenomena (such as radioactive signatures from mid-twentieth-century nuclear testing), the term becomes decoupled from the very thing it was intended to define, since the vast majority of humanity had no part in creating such a layer.
“Human impacts on the landscape…and on the environment, didn’t start at the same time everywhere on Earth. If you live in China, these things began 5,000 or more years ago. If you live in North America, they seem to have begun roughly in the 1700s…To draw a single line – which is what geologists have to do – that is the same age everywhere on the Earth’s surface, we have to have [a global] event. Either a change in the biology…or some change in the physical environment such as the geochemistry.” – Paul Gibbard, Secretary General, International Commission on Stratigraphy
Although there is no merit to a geological definition of the ‘Anthropocene,’ it is still a valuable anthropological (and especially archaeological) term. Just as the Three Age System can be applied in certain situations to locally parse prehistory, so too could a localized ‘Anthropocene’ be used to discuss a tipping point after which man’s impact on the environment resulted in observable changes in the behavior of that particular group. The resulting feedback loops could then be compared between sites to find patterns, and those patterns could be investigated to uncover commonalities that resulted in both successful and unsuccessful strategies.