This article originally appeared on Yahoo News.
The reason there has never been a confirmed sighting of an alien – or a message from an alien race – could be very depressing.
The reason we haven’t heard from aliens is because they’re all already dead, a new study has suggested.
Researchers from Australian National University suggest that the environments on early planets tend to be so hostile that even when life arises, it is quickly exterminated.
‘The Universe is probably filled with habitable planets, so many scientists think it should be teeming with aliens,’ said Aditya Chopra from the Australian National University.
‘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.’’
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