This is article went off the rails when it talked about evidence for past civilizations on Earth being undetectable: > The only real evidence after a million o

This is article went off the rails when it talked about evidence for past civilizations on Earth being undetectable: > The only real evidence after a million or more years would boil down to isotopic or chemical stratigraphic anomalies—odd features such as synthetic molecules, plastics or radioactive fallout. Civilization on the scale such as ours creates huge waves of extinctions in the planet's species leaving lots of evidence easily available for us to see that it happened. In addition we've affected the Earth's atmosphere with our carbon emissions and that's going to leave evidence behind as well that will last a very long time. Also, all that easily accessible oil that we've been using to power our engines would not exist, because nobody is going to be leaving such an abundant and easy to use source of fuel around. The oil and gas we use took tens and hundreds of millions of years to form. Finally, and not least of all, the quoted paragraph mentions radioactive fall out, but any radioactivity would be blatantly obvious unless this civilization used none of it. There would be a very clear indicator in our dating methods of any radioactive activity in the past. I think it's safe to presume that instead of some past civilization that didn't use the most abundant natural source of energy around, didn't make use of nuclear energy and somehow managed to leave the species record clean it simply didn't exist. I don't feel like it takes more than a few moments to just realize how unlikely that take is and shouldn't have been included in the article.