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Our Milky Way galaxy contains tens of billions of potentially habitable planets, but we have no idea whether we’re alone. For now Earth is the only world known to harbor life, and among all the living things on our planet we assume Homo sapiens is the only species ever to have developed advanced technology.

But maybe that’s assuming too much.

In a mind-bending new paper entitled “The Silurian Hypothesis” — a reference to an ancient race of brainy reptiles featured in the British science fiction show “Doctor Who” — scientists at NASA’s Goddard Institute for Space Studies and the University of Rochester take a critical look at the scientific evidence that ours is the only advanced civilization ever to have existed on our planet.

“Do we really know we were the first technological species on Earth?” asks Adam Frank, a professor of physics and astronomy at Rochester and a co-author of the paper. “We’ve had an industrial society for only about 300 years, but there’s been complex life on land for nearly 400 million years.”

If humans went extinct today, Frank says, any future civilization that might arise on Earth millions of years hence might find it hard to recognize traces of human civilization. By the same token, if some earlier civilization existed on Earth millions of years ago, we might have trouble finding evidence of it.


The discovery of physical artifacts would certainly be the most dramatic evidence of a Silurian-style civilization on Earth, but Frank doubts we’ll ever find anything of the sort.

“Our cities cover less than one percent of the surface,” he says. Any comparable cities from an earlier civilization would be easy for modern-day paleontologists to miss. And no one should count on finding a Jurassic iPhone; it wouldn’t last millions of years, Gorilla Glass or no…Read More at

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