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Astrobiologists have a new theory for why we haven't found aliens: They're all extinct

Astrobiologists from the Australian National University Research School of Earth Sciences suggest that the reason why we haven't encountered alien life is because all the aliens are extinct, the university reported Thursday. In studying how life might develop on other planets, the scientists realized that early critters likely had a hard time quickly evolving to their heating or cooling planets and did not survive.

"Early life is fragile, so we believe it rarely evolves quickly enough to survive. Most early planetary environments are unstable. To produce a habitable planet, life forms need to regulate greenhouse gases such as water and carbon dioxide to keep surface temperatures stable," Dr. Aditya Chopra said in the paper publishing the astrobiologists' findings.

"Life on Earth probably played a leading role in stabilizing the planet's climate," co-author Associate Professor Charley Lineweaver said.

The paradox of astrobiology is that many planets likely check all the boxes for being habitable for life, but we have yet to discover any. The researchers have named their solution to this paradox the "Gaian Bottleneck." "One intriguing prediction of the Gaian Bottleneck model is that the vast majority of fossils in the universe will be from extinct microbial life, not from multicellular species such as dinosaurs or humanoids that take billions of years to evolve," Lineweaver said.