Silurians found by Doctor Who. Promotional material to illustrate the subject in question is fair use, or so says Wikipedia.
Deep within our history,
Four hundred million years ago,
One of the greatest dyings cleared
The Earth for them to grow.
Boney fish with moving jaws
Dodged scorpions in the shallow seas,
Hardly social it would seem,
Yet something walked the land near these.
Abundant layers, weirdly thick,
Industry spewed pollution slicks.
Suggestion of dead ocean zones,
Imply farming on
a scale vast.
That’s civilization evidence.
Not to mention oddly high
Concentrations to be found
Of antimony, lead, and chrome,
Rare earths, and gold within the ground.
Sudden population booms
Of crinoids and certain trilobites,
Indicator species these,
Shape of lipids well preserved
Not mono-chiral indicates
They were made
Until the late Devonian,
When life in deep oceans died,
Anoxia that changed the seas
Sent glaciers south to crush their lives.
No, there are no real facts
But to think of traces
they could have left
May help us search the starry skies.
by Kate Rauner
Silurian fossils, but, no, that’s not a Silurian coin. It’s just there to indicate size.
Thanks to theatlantic for their story on this study published in the International Journal of Astrobiology: could we tell if an advanced civilization existed on Earth long before humans, even before mammals?
Such conjecture may help us ponder extraterrestrials. As the authors say, “While much idle speculation and late night chatter has been devoted to this question, we are unaware of previous serious treatments of the problem of detectability of prior terrestrial industrial civilizations in the geologic past.” Download the pdf for yourself.