Ever since seventeenth-century Danish scientist Nicholas Steno first came up with the idea that rock formations were stratified into horizontal layers according to the periods of time they were laid upon one another, geologists have attempted to discern the different geological time scales of the earth.
With each distinctive rock layer, or strata, came different types of fossils, chemical concentrations and weather patterns, indicating that there was a relationship between the life forms, the atmospheric concentration of particular gases (in particular oxygen and carbon dioxide) and particular events (such as ice ages, volcanic eruptions or asteroid impacts, to name a few) of that point in time.
Even though the scientific knowledge and technology has progressed, the chronological ordering of geological time scales has remained a controversial topic. Nevertheless, a formal taxonomy has formed over the years – arbitrated by an International Commission on Stratigraphy (ICS) – which divides the history of the earth into different geochronological subsets, starting from eons, and broken down further into eras, periods, epochs and ages.
Under this nomenclature, we are currently in the Subatlantic age of the Holocene epoch of the Quaternary period of the Cenozoic era of the Phanerozoic eon. The Holocene epoch is the most relevant and important to us because it is the prime reason human civilisation has been able to flourish.
The Holocene, which began around 11,000 to 12,000 years ago, is an interglacial phase of the current ice age, meaning it is a period of stable, warm climate in between the advances of continental ice sheets (known as glacial periods). This warm, stable Holocene climate has been very accommodating to humans all over the globe – who entered into the period largely as hunter-gatherers and foragers – and allowed them to settle down in specific areas to begin agrarian lifestyles.
The consequent Agricultural Revolution, beginning approximately 8000 years ago, created a huge increase in the amount of nutritional energy available for humans, leading to a massive explosion of the human population.
Through the advent of agriculture, two major environmental milestones happened: firstly, humans began selectively breeding animals and plants to harness their energy and work in unprecedented ways; and secondly, humans began establishing surpluses of food.
These surpluses led to the establishment of complex societies and political states, as no longer did every human need to expend energy on hunting and gathering their own food.
Soon enough, a division of labour formed, and people could dedicate their lives to being doctors, or priests, or engineers, or soldiers. This in turn allowed for specialisation, and would pave the way for further technological and scientific advancement.
Such progression would eventually spurn the Industrial Revolution of the eighteenth century, and the massive environmental implications it caused. It has been these man-made environmental changes, and their striking deviations from Holocene conditions, that have largely led a groundswell of scientists to argue that Earth has passed into a new geological epoch: the Anthropocene (derived from ancient Greek words denoting “man” and “change”).
A formal expression of this groundswell, the Anthropocene Working Group, has been trying to persuade the ICS and the rest of the geological community to adopt the Anthropocene as the current geological epoch.
To this day, the Anthropocene has had its critics and is yet to be formally adopted. However a recent Anthropocene Working Group study, published in the journal Science, demonstrating all the evidence so far that we’ve passed through into the Anthropocene, is making waves.
For my next blog, I speak to one of the study’s research authors, an Australian scientist, about the work.