With an unusual drop in atmospheric carbon dioxide and the irreversible exchange of species between the New and Old Worlds, the human-dominated geological epoch known as the Anthropocene probably began around in 1610, a research shows.
"The Anthropocene probably began when species jumped continents, starting when the Old World met the New. We humans are now a geological power in our own right - as Earth -changing as a meteorite strike," explained lead author Simon Lewis from the University College London (UCL).
The study authors systematically compared the major environmental impacts of human activity over the past 50,000 years.
Just two dates met the criteria: 1610 when the collision 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 subsequent global trade, moved species to new continents and oceans, resulting in a global re-ordering of life on Earth. This rapid cross-ocean exchange of species is without precedent in Earth's history," researchers from the University College London and University of Leeds explained.
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The first fossil pollen of maize, a Latin American species, appears in marine sediment in Europe in 1600, becoming common over subsequent centuries.
This irreversible exchange of species satisfies the first criteria for dating an epoch - long-term changes to Earth.
The researchers also found a pronounced dip in atmospheric carbon dioxide centred on the year 1610 and captured in Antarctic ice-core records.
The drop occurred as a direct result of the arrival of Europeans in the Americas.
Till date, the beginning of the Industrial Revolution in the late 18th century has most commonly been suggested as the start of the Anthropocene.
However, the researchers did not find this a right candidate because most effects were local, while the global exponential rise in carbon dioxide was too smooth an increase to form a precisely dated marker.
"A more wide-spread recognition that human actions are driving far-reaching changes to the life-supporting infrastructure of Earth will have implications for our philosophical, social, economic and political views of our environment," added study co-author professor Mark Maslin from the UCL.
The paper appeared in the journal Nature.