If you've ever looked up into the unfathomable night sky and wondered, "Are we alone?" then you are not alone.
About 70 years ago, physicist Enrico Fermi looked up into the sky and asked a similar question: "Where is everybody?"
There are hundreds of billions of stars in the Milky Way galaxy alone, Fermi reckoned, and many of them are billions of years older than our sun. Even if a small fraction of these stars have planets around them that proved habitable for life (scientists now think as many as 60 billion exoplanets could fit the bill), that would leave billions of possible worlds where advanced civilizations could have already bloomed, grown and — eventually — begun exploring the stars.
So, why haven't Earthlings heard a peep from these worlds? Where is everybody? Today, this question is better known as the Fermi paradox. Researchers have floated many possible answers over the years, ranging from "The aliens are all hiding underwater," to "They all died," to "Actually, we are the aliens, and we rode a comet to Earth a few billion years ago." [12 Possible Reasons We Haven't Found Aliens]
Now, Alexander Berezin, a theoretical physicist at the National Research University of Electronic Technology in Russia, has proposed a new answer to Fermi's paradox — but he doesn't think you're going to like it. Because, if Berezin's hypothesis is correct, it could mean a future for humanity that's "even worse than extinction."
"What if," Berezin wrote in a new paper posted March 27 to the preprint journal arxiv.org,"the first life that reaches interstellar travel capability necessarily eradicates all competition to fuel its own expansion?"
In other words, could humanity's quest to discover intelligent life be directly responsible for obliterating that life outright? What if we are, unwittingly, the universe's bad guys?
First in, last out
In the paper, Berezin called this answer to Fermi's paradox the "first in, last out" solution. Understanding it requires narrowing down the parameters of what makes "intelligent life" in the first place, Berezin wrote.
For starters, it doesn't really matter what alien life looks like; it could be a biological organism like humans, a superintelligent AI or even some sort of planet-size hive mind, he said.
But it does matter how this life behaves, Berezin wrote. To be considered relevant to Fermi's paradox, the extraterrestrial life we seek has to be able to grow, reproduce and somehow be detectable by humans. That means our theoretical aliens have to be capable of interstellar travel, or at least of transmitting messages through interstellar space. (This is assuming humans don't reach the alien planet first.)
Here's the catch: For a civilization to reach a point where it could effectively communicate across solar systems, it'd have to be on a path of unrestricted growth and expansion, Berezin wrote. And to walk this path, you'd have to step on a lot of lesser life-forms.
"I am not suggesting that a highly developed civilization would consciously wipe out other lifeforms," Berezin wrote. "Most likely, they simply won't notice, the same way a construction crew demolishes an anthill to build real estate because they lack incentive to protect it."
For example, a rogue AI's unrestricted drive for growth could lead it to populate the entire galaxy with clones of itself, "turning every solar system into a supercomputer," Berezin said. Looking for a motive in the AI's hostile takeover is useless, Berezin said — "all that matters is that it can [do it]."
A fate worse than extinction
The bad news for humans isn't that we might have to face off against a power-crazed race of intelligent beings. The bad news is, we might be that race. "We are the first to arrive at the [interstellar] stage," Berezin speculated, "and, most likely, will be the last to leave."
Stopping humans from accidentally obliterating all rival life-forms would require a total culture shift spurred by "forces far stronger than the free will of individuals," Berezin wrote. Given our species' impressive talent for expansion, however, such forces could be hard to muster.
Then again, this is all just a theory. The paper has yet to be peer-reviewed by fellow scientists, and even Berezin is rooting against his own conclusions.
"I certainly hope I am wrong," Berezin wrote. "The only way to find out is to continue exploring the universe and searching for alien life."
Originally published on Live Science.
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Brandon has been a senior writer at Live Science since 2017, and was formerly a staff writer and editor at Reader's Digest magazine. His writing has appeared in The Washington Post, CBS.com, the Richard Dawkins Foundation website and other outlets. He holds a bachelor's degree in creative writing from the University of Arizona, with minors in journalism and media arts. He enjoys writing most about space, geoscience and the mysteries of the universe.