The idea that an advanced civilization existed on Earth long before humans is fascinating, but scientists aren't convinced. Experts have explored this possibility by asking what traces a technological ...

Add Yahoo as a preferred source to see more of our stories on Google. The fossilized tail bones of an Ichthyosaurus, around 190 million years old and weighing 800 kilograms. - Markus Scholz/picture ...

The Silurian Hypothesis asks whether signs of truly ancient past civilizations would even be recognisable today.

(CNN) — When astrobiologist Adam Frank walked into the office of NASA scientist Gavin Schmidt, he had what he believed was the weirdest question: do aliens experience climate change? It took just ...