![]() ![]() It would be easy, therefore, to miss an industrial civilization that lasted only 100,000 years-which would be 500 times longer than our industrial civilization has made it so far. But the fraction of life that gets fossilized is always minuscule and varies a lot depending on time and habitat. So could researchers find clear evidence that an ancient species built a relatively short-lived industrial civilization long before our own? Perhaps, for example, some early mammal rose briefly to civilization building during the Paleocene epoch, about 60 million years ago. That means the question shifts to other species, which is why Gavin called the idea the Silurian hypothesis, after an old Doctor Who episode with intelligent reptiles. Homo sapiens didn’t make their appearance on the planet until just 300,000 years or so ago. Go back much further than the Quaternary, and everything has been turned over and crushed to dust.Īnd, if we’re going back this far, we’re not talking about human civilizations anymore. It’s “just” 1.8 million years old-older surfaces are mostly visible in cross section via something like a cliff face or rock cuts. For example, the oldest large-scale stretch of ancient surface lies in the Negev Desert. ![]() When it comes to direct evidence of an industrial civilization-things like cities, factories, and roads-the geologic record doesn’t go back past what’s called the Quaternary period 2.6 million years ago. But once you roll the clock back to tens of millions or hundreds of millions of years, things get more complicated. These kinds of artifacts of previous societies are fine if you’re only interested in timescales of a few thousands of years. We’re used to imagining extinct civilizations in terms of sunken statues and subterranean ruins. Though neither of us could see it at that moment, Gavin’s penetrating question opened a window not just onto Earth’s past, but also onto our own future. Instead, that first conversation launched a new study we’ve recently published in the International Journal of Astrobiology. “Could we tell if there’d been an industrial civilization that deep in time?” Sitting there, seeing Earth’s vast evolutionary past telescope before my mind’s eye, I felt a kind of temporal vertigo. I had certainly come into Gavin’s office prepared for eye rolls at the mention of “ exo-civilizations.” But the civilizations he was asking about would have existed many millions of years ago. It took me a few seconds to pick up my jaw off the floor. “How do you know we’re the only time there’s been a civilization on our own planet?” Just as I was revving up my pitch, Gavin stopped me in my tracks. I was visiting GISS that day hoping to gain some climate-science insights and, perhaps, collaborators. In my work as an astrophysicist, I’d begun researching global warming from an “astrobiological perspective.” That meant asking whether any industrial civilization that rises on any planet will, through its own activity, trigger its own version of a climate shift. One day last year, I came to GISS with a far-out proposal. GISS), a world-class climate-science facility. Schmidt is the director of NASA’s Goddard Institute for Space Studies (a.k.a. It only took five minutes for Gavin Schmidt to out-speculate me. This article was featured in One Story to Read Today, a newsletter in which our editors recommend a single must-read from The Atlantic, Monday through Friday. ![]()
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