The Anthropocene epoch, a geological epoch where humans dominated the earth, probably began around the year 1610. An unusual drop in atmospheric carbon dioxide and the irreversible exchange of species between the New and Old Worlds marked this new global epoch, according to new research published in Nature. Defining an “epoch” requires two main criteria to be met. Long-lasting changes to the Earth must be documented. Scientists must also pinpoint and date a global environmental change that has been captured in natural material, such as rocks, ancient ice or sediment from the ocean floor. The combination of multiple environmental changes being documented in multiple materials around the globe is called a “golden spike.” The study authors systematically compared the major environmental impacts of human activity over the past 50,000 years to see when fit these two formal requirements. Only two dates met both criteria: 1610, when the discovery and joining of the Americas and Eurasian/Africa first affected the entire globe; and 1964, when global environmental changes occurred due to the fallout from nuclear weapons tests. The researchers concluded that 1610 is the stronger candidate.
The scientists say the 1492 arrival of Europeans in the Americas, and subsequent global trade, moved species to new continents and oceans, resulting in a global re-ordering of life on Earth. This rapid, repeated, cross-ocean exchange of species is without precedent in Earth’s history. The first fossil pollen of maize appears in marine sediment in Europe in 1600. The researchers argued that the joining of the two hemispheres is an unambiguous event after which the impacts of human activity became global and set Earth on a new trajectory. The researchers also found a golden spike that can be dated to the same time: a pronounced dip in atmospheric carbon dioxide centred on 1610 and captured in Antarctic ice-core records. The drop occurred as a direct result of the arrival of Europeans in the Americas. Colonisation of the New World led to the deaths of about 50 million indigenous people, most within a few decades of the 16th century due to smallpox. The abrupt near-cessation of farming across the continent and the subsequent re-growth of Latin American forests and other vegetation removed enough carbon dioxide from the atmosphere to produce a drop in CO2. Thus, the second requirement of a golden spike marker is met.
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