This is actually a somewhat active area of research https://en.wikipedia.org/wiki/Silurian_hypothesis https://en.wikipedia.org/wiki/Silurian_hypothesis The abs

This is actually a somewhat active area of research https://en.wikipedia.org/wiki/Silurian_hypothesis https://en.wikipedia.org/wiki/Silurian_hypothesis The absence of detectable plutonium-244 (half-life of 81.3 million years) is one indication that we are ~probably the first civilization on Earth to discover nuclear fission.