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? Will homo sapiens, in other words, define a geological period in the way dinosaurs — and their vanishing act — helped mark the Jurassic and the Cretaceous?
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 realization 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.
“Zalasiewicz must recognize the implications for society if his own tribe decides, using classical criteria, that there is not yet enough evidence to formally recognize a new boundary in the geological record,” said Bryan Lovell, president of the British Geological Society and a professor at Cambridge.