2018-04-15, 03:02 PM
Was There a Civilization On Earth Before Humans?
Quote:“Wait a second,” he said. “How do you know we’re the only time there’s been a civilization on our own planet?”
It took me a few seconds to pick my jaw off the floor. 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. Sitting there, seeing Earth’s vast evolutionary past telescope before my mind’s eye, I felt a kind of temporal vertigo. “Yeah,” I stammered, “Could we tell if there’d been an industrial civilization that deep in time?”
We never got back to aliens. Instead, that first conversation launched a new study we’ve recently published in the International Journal of Astrobiology. 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.
We’re used to imagining extinct civilizations in terms of the sunken statues and subterranean ruins. These kinds of artifacts of previous societies are fine if you’re only interested in timescales of a few thousands of years. But once you roll the clock back to tens of millions or hundreds of millions of years, things get more complicated.
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. For example, the oldest large-scale stretch of ancient surface lies in the Negev Desert. 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. Go back much farther than the Quaternary and everything has been turned over and crushed to dust.
And, if we’re going back this far, we’re not talking about human civilizations anymore. Homo sapiens didn’t make their appearance on the planet until just 300,000 years or so ago. That means the question shifts to other species, which is why Gavin called the idea the Silurian hypothesis, after an old Dr. Who episode with intelligent reptiles.
So, could researchers find clear evidence that an ancient species built a relatively short-lived industrial civilization long before our own?
(the smilie means I'm trying to be funny - not laughing at you, laughing at my joke)