The Anthropocene
When did it start exactly?
Before I will attempt to give an answer to the question I posed above, I should try and give a definition of what one means by the Anthropocene. The Anthropocene is an unofficial geological and ecological epoch¾a formal unit of geological time used to divide the Earth’s history into measurable segments based on distinct changes in rock layers, fossil records, and climate¾defined by the profound, irreversible impact of human activity on the Earth. Unlike other epochs, the Anthropocene has as yet no agreed upon physical indicator, referred to as “golden spikes”, that marks its beginning.
The best-known golden spike is in fact not made of gold but of bronze. And it is not even a spike but a plaque. The Ediacaran “golden spike”, found along Enorama Creek in the Ikara-Flinders Ranges national park in South Australia, marks the end of the Marinoan glaciation, when the planet resembled a ball of ice. The end of that deep global freeze triggered the evolution of the first multicellular organisms, the Ediacaran fauna. These creatures featured prominently in the first-year biology lectures I used to give, not just because they were truly bizarre, but also because they were the first complex animals found in the fossil record. Their reign ended with the start of the Cambrian period when the weirdos were replaced by the kind of animal forms we know today. The end of the Ediacaran period and the start of the Cambrian is officially marked at Fortune Head, Newfoundland in Canada. This “golden spike” isn’t made of gold either. None of them are, in fact, because the 80 or so official geological “golden spikes” are named in honour of the famous Utah railway golden spike that marked the completion of the United States’ first transcontinental railroad. You can see the actual golden spike at the Cantor Arts Centre at Stanford University in California.
In the previous post, We are still evolving, I mentioned the Holocene, the start of the milder climate following the last ice age that allowed the development of agriculture. Agriculture changed our species forever as it allowed humans to live in much larger groups. And with rapid increases in human populations came the beginning of urbanization. So, in effect, the Holocene is already significantly influenced by human activity. What, then, is new about the Anthropocene?
Loads of things, apparently. I was initially rather sceptical about the concept of the Anthropocene, as I felt that dedicating an epoch to the influence of one species, us, is not only self-centred but also implies that there has been a shift from us being part of the natural environment to us having “stepped out” and exerting a disproportional (unnatural?) negative effect on that environment. So let us have a look at the most frequently used global markers for the Anthropocene. Such markers should be some sort of “line in the sand” across the entire planet.
The sharpest and most globally synchronous signal is the so-called bomb spike, the sudden massive spike in plutonium and other radioisotopes caused by above-ground testing of thermonuclear weapons in the early 1950s. Plutonium isotopes in particular, are now found in sediments, coral growth rings, and ice cores worldwide, so creating a permanent timeline centred around 1952.
A decent second “golden spike” are the chemical signatures trapped in sedimentary layers that were the result of the “Great Acceleration”, the massive post-World War II surge in industrialization. The burning of fossil fuel, particularly at high temperatures, creates spherical carbonaceous particles known as fly ash which can now be found as black spheres in lake beds and glacial ice. The heavy burning of fossil fuels also disrupted the natural ratio of carbon isotopes in the atmosphere. Synthetic chemical fertilizers did the same for nitrogen isotopes.
As if the above two disruptions were not enough, we also created materials that were never seen before, think plastics, concrete, elemental aluminium, synthetic fibers and electronic waste, that will stay with us preserved in the rock record for millions of years. They are therefore known as technofossils, which sounds much cuter than they are in reality.
In addition to dramatically shifting the Earth’s equilibrium by bombing, burning and creating stuff, we have also significantly changed the biology of our planet. I now live in the land of koalas and kangaroos, both marsupials. Australia hardly had any native placental mammals other than seals, dugongs and a species of bat, until about 5,000 years ago when seafaring humans introduced what we now call dingoes. Things got really out of whack with the arrival of Europeans who brought with them the flora and fauna they knew and loved. Human migrations have completely broken down the natural boundaries that kept species separate for millions of years, resulting not only in global homogenization but also causing massive problems when introduced species become invasive. If that is not bad enough, thanks to animal husbandry, the number of domesticated animals now vastly outnumbers wild animals. The broiler chicken is another good candidate for the Anthropocene’s “golden spike” as the bones of the domesticated chicken make a sudden, massive appearance in the landfills of industrial countries.
Despite the significant and negative effects that our behaviour clearly has and continues to have on the planet, none of the above count as official “golden spikes”. Thus, at this moment in time the Anthropocene is merely an intellectual concept.
Real or not, I wonder if in our attempt to define the Anthropocene we are placing too much emphasis on industrialised societies. Perhaps we should even go much further back in time, when our ancestors started to use fire to reshape landscapes. The great man Charles Darwin regarded the ability to control fire as the greatest discovery made by humanity, second only to language. Perhaps humanity’s disproportional influence on Earth is much older that we tend to think.
More in the next post.
PS. After finishing this essay I bumped into the following piece in which a geologist tries to figure out what a rock is: https://aeon.co/essays/the-strange-rocks-that-wouldnt-exist-without-us