The Paleozoic Era, between 541 and 252 million years ago, was a remarkable time for new life on Earth. It started with the Cambrian explosion, the largest diversification event of life forms in Earth’s history. It led to lush rainforests, the emergence of fish, and, eventually, the transition of amphibians to land.

But all good things must come to an end. The remarkable Paleozoic Era ended with the largest mass extinction of life forms in Earth’s history. An abrupt shift to global warming caused a major marine and terrestrial extinction event. This sudden Permian-Triassic Extinction event eliminated more than 80% of all marine species and 70% of terrestrial vertebrate species. It buried plants and swamps, which were subsequently compacted and cooked into underground coal deposits.

Popular opinion holds that an asteroid impact triggered the Permian-Triassic extinction and that humanity was the first technological civilization on Earth 250 million years later.

Is it possible that the devastating global warming event was caused 252 million years ago by industrial pollution from a technological civilization? This would have required the first intelligence to emerge only 6 percent earlier in the 4,540-million-year history of Earth.

Any technological infrastructure left on the surface of Earth from that early civilization could have been demolished by geological activity, including subduction, coverage by water, or tarnishing by meteor impacts and weathering.

However, functional relics could have been preserved in space.  Within the past century of modern technology, our civilization has launched many thousands of functional devices in orbit around Earth. A more advanced or longer-lived technological civilization could have used more sophisticated devices. Are there unfamiliar technological relics in our sky?

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