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Epoch-defining study pinpoints when humans came to dominate planet Earth

Simon and Mark’s conclusions published in Nature

Epoch-defining study pinpoints when humans came to dominate planet Earth

Dr Simon Lewis and Professor Mark Maslin (UCL Geography) have concluded, in a paper published by Nature on March 12th, that humans have become a geological power, and that human actions have produced a new geological epoch.

They argue that the human-dominated geological epoch known as the Anthropocene probably began around the year 1610, with an unusual drop in atmospheric carbon dioxide and the irreversible exchange of species between the New and Old Worlds.

Simon and Mark systematically compared the major environmental impacts of human activity over the past 50,000 years against the established formal requirements for a geological epoch. Just two dates met the criteria: 1610, when the interaction of the New and Old Worlds a century earlier was first felt globally; and 1964, associated with the fallout from nuclear weapons tests. The researchers conclude that 1610 is the stronger candidate.

The 1492 arrival of Europeans in the Americas, and the subsequent global trade, moved species to new continents and oceans, and thus resulted in a global re-ordering of life on Earth. This rapid, repeated, cross-ocean exchange of species is without precedent in the Earth’s history.

They argue that joining the two hemispheres is an unambiguous event, after which the impacts of human activity became global, setting the Earth on a new trajectory. The first fossil pollen of maize, a Latin American species, appeared in European marine sediment in 1600, and became common during subsequent centuries. Such an irreversible exchange of species satisfies the first requirement for dating an epoch – long-term changes to the Earth.

The researchers also found a “golden spike” dating to the same time - a pronounced dip in atmospheric carbon dioxide centred on 1610 and captured in Antarctic ice-core records. The dip occurred as a direct result of the arrival of Europeans in the Americas.

New World colonisation led to the deaths of about 50 million indigenous peoples, mostly within a few 16th century decades, 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 the drop in CO2. Thus, the second requirement, of a golden spike marker, is met.

The researchers have named the 1610 dip in carbon dioxide the ‘Orbis Spike’. They chose the Latin word for ‘world’ because this golden spike was caused by once-disconnected peoples becoming globally linked.


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(c) Nature/Alberto Seveso

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