LONDON: If alien geologists were to visit our planet 10 million years from now, would they discern a distinct human fingerprint in Earth’s accumulating layers of rock and sediment?

For the first time in Earth’s 4.7 billion year history, a single species has not only radically changed Earth’s morphology but also reshaping it.

A growing number of scientists, some gathered at a one-day symposium this week at the British Geological Society in London, say “yes”.

One among them, chemistry Nobel laureate Paul Crutzen, has even suggested a new name: the Anthropocene.

Whether this “age of man” will be short or long is unknown. But one thing is clear, says Crutzen, who shared his Nobel for unmasking the man-made chemicals eating away at the atmosphere’s protective ozone layer.

For the first time in Earth’s 4.7 billion year history, a single species has not only radically changed Earth’s morphology, chemistry and biology, it is now aware of having done so.“We broke it, we bought it, we own it,” is how Erle Ellis, a professor of geography and ecology at the University of Maryland at Baltimore, put it.

“We don’t know what is going to happen in the Anthropocene – it could be good, even better,” he said. “But we need to think differently and globally, to take ownership of the planet.” Dinosaurs were most likely wiped out by a giant meteor that cooled Earth’s temperatures below their threshold for survival.

An analogous fate could await humans if temperatures climb by five or six degrees Celsius, which climate scientists say could happen within a century.

But dinosaurs thrived for more than 150 million years before a cosmic pebble ended their extraordinary run, while modern humans have only been around for about 200,000 years, a snap of the fingers by comparison.

Another key difference: dinosaurs didn’t know what hit them, and played no role in their own demise.

Humans, by contrast, have been the main architects of the enormous changes that are threatening to throw what scientists now call the Earth System out of whack.

Since Crutzen coined the term a decade ago, the Anthropocene has been eagerly adopted by scientists across a broad spectrum of disciplines.“It triggered the realisation that we were in an entirely new era of planet Earth,” said Will Steffen, head of Australian National University’s Climate Change Institute.It also triggered fierce debate.

At one level, the issues are narrow to the point of pedantry – rock experts quibbling over whether mankind’s present and future geological imprint merits recognition by the International Commission on Stratigraphy.

At the same time, however, the concept forces us to ponder whether humanity’s outsized impact on the planet could lead to undesired, possibly uncontrollable, outcomes, and what, if anything, humanity should do about it.

That leaves scientists who may be more comfortable classifying rocks than rocking the boat in a tricky position.

‘Sculpting the Earth’

For now, the man in the hot seat is University of Leicester professor Jan Zalasiewicz, who heads the group of geologists tasked with recommending whether the Anthropocene should be added to the 150-odd eons, eras, periods, epochs and ages into which the last 3.6 billion years of Earth’s history has been officially divided.

“Jan must recognise the implications for society if his own tribe decides, using classical criteria, that there is not yet enough evidence to formally recognise a new boundary in the geological record,” said Bryan Lovell, president of the British Geological Society and a professor at Cambridge.

Evidence of abrupt change – on a geological time scale – wrought by human hands would seem to be overwhelming.

The burning of fossil fuels has altered the composition of the atmosphere, pushing the concentration of carbon dioxide to levels unseen at least for 800,000 years, perhaps for three million.

The resulting global warming has itself set in motion other planetary-scale changes: massive melting of the parts of Earth normally covered by ice and snow (aka the cryosphere), and the acidification of the oceans.

Past shifts in the biosphere – the realm of the living – show up in sediment and rock, especially mass extinctions that have seen up to 90 percent of all lifeforms disappear within the geological blink of an eye.

There have been five such wipeouts over the last half billion years, and most scientists agree that we have now entered the sixth, with species disappearing at 100 to 1,000 times the so-called “background” rate.Another key index is the rise of invasive species travelling in a globalised world via ship ballasts, air travel and old-fashioned smuggling.

“The mass homogenisation event” – finding the same species everywhere – “will be quite a clear signal in the archaeological record a million years from now,” said Zalasiewicz.