In Bugonia, it all starts with bees. A warehouse worker, Teddy (played by Jesse Plemons), accuses high-powered CEO Michelle (Emma Stone) of being an extraterrestrial who is secretly killing bees, disrupting the ecosystems humans depend on for food.
“The signs,” Teddy says, “are obvious.”
It’s a funny and gripping premise. But at the center of the movie is a compelling question that scientists all over the world are working to answer: How would we know if we saw an alien?
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To identify alien life, scientists must be able to tell that the thing they are considering is alive. But there’s not as much consensus about what “life” really is as you might think.
"We don’t have a really clear theoretical and experimental program to ask questions about the nature of life,” says Sara Walker, an astrobiologist and theoretical physicist at Arizona State University. Essentially, our working criteria are based exclusively on life on Earth. But across the vastness of the universe, life might present as radically different from what we’ve seen on our planet.
Walker theorizes that life may not have to be based on organic molecules, cells and DNA, for example. Rather it might be easier to identify life using what she and her colleagues call “assembly theory,” which means spotting complex systems that stem from traceable lineages and that have changed their environment in a way that only a living entity could.
What might that look like beyond Earth? Well, we have no idea—yet. “The vast possibility space [of] life far exceeds both what has been actualized here on Earth in our one single biosphere and also potentially our imaginations,” says Mike Wong, an astrobiologist at the Carnegie Institution for Science’s Earth & Planets Laboratory.
Every living thing on Earth has been honed by millions of years of evolution and coevolution alongside all the other creatures and the planet’s different environments. It’s reasonable to assume that an alien probably won’t look anything like an Earthling, Wong says, because its evolutionary history could be determined by a radically different world with unique pressures and environments.
And as for Bugonia, “I think it would be highly unlikely that aliens would look like Emma Stone,” Wong says.
Even small distinctions between worlds can change evolutionary outcomes a lot. For example, take two identical Earths, says Nathalie Cabrol, an astrobiologist and director of the Carl Sagan Center for Research at the SETI Institute, a non-profit dedicated to searching for extraterrestrial intelligence. If one Earth has a fraction of a second’s difference in its orbit than the other, then it’s possible that “evolution is going to be drastically different,” she says. “You are going to have extinctions that are not timed the same way. You are going to be hit by more asteroids, or you are going to avoid one,” she speculates.
But for argument’s sake, let’s say an alien, as proposed in Bugonia, happens to look a lot like us. How would we know it wasn’t a human?
The last universal common ancestor of all life on Earth, known as LUCA, is embedded in every being’s genes. Because everything alive arose from LUCA, plants, animals and microbes all share certain basic traits, such as storing genetic information in DNA and RNA. Alien life, ostensibly, would have originated somewhere else and thus not share this common ancestor. As a result, the alien almost certainly wouldn’t have the same basic chemical or genetic building blocks that all life on Earth shares—and a simple genetic test would reveal that, Wong says.
As unlikely as it is that we will ever encounter an alien that just so happens to look like Emma Stone, Bugonia shows how fictional stories about aliens tend to be wrapped up in very real human problems, the SETI Institute’s Cabrol says.
“Why would I start looking at someone and say, ‘You are an alien’?” she says. “Is there something in our society today that says, ‘You look like something I can recognize, but it’s not really us’?”