A New Study Predicts 4 Hostile Alien Civilizations May Be Prowling the Milky Way

Luckily the chances of a hostile alien civilization finding us are negligible.
hostile alien

According to a new study by Ph.D. student Alberto Caballero, the Milky Way may be home to four hostile alien civilizations that would conquer Earth if they could. His research is published in the preprint database arXiv.

Why should we care what a Ph.D. student thinks? 

What makes other media news coverage of this story interesting is that Caballero is not an astrophysicist. Caballero studies conflict resolution at the University of Vigo in Spain, making press coverage of his opinion even more bizarre until you explore some exciting statistics that Caballero applied to his research to arrive at his theory.

Caballero has given his views on aliens and outer space before. He previously researched the Wow! Signal and his research was accepted and published in the peer-reviewed International Journal of Astrobiology.


What makes Alberto Callero’s research into calculating the number of hostile alien civilizations fascinating is how he arrived at his meticulous calculation that as many as four hostile alien civilizations exist in the Milky Way.

Callero’s calculation of hostile aliens in the Milky Way has had some inspiration from SETI experts who, in 2012, published in Mathematical SETI, said that, based on potentially habitable planets in our galaxy, as many as 15,785 alien civilizations might conceivably coexist with humans in the galaxy.

Allen Telescope Array Flickr brewbooks
SETI Allen Telescope Array by brewbooks under CC BY-SA 2.0

In Callero’s calculation of what percentage of these potential alien civilizations could be hostile or a threat to us, his research becomes a combination of anthropology, history, and math, examining human behavior and conflicts. Now the relevance of his study area of conflict resolution comes to the fore.


Analyzing the history of human conflict to calculate the probability of hostile aliens attacking Earth

Caballero noted in his paper that he seeks to evaluate the prevalence of hostile alien civilizations by extrapolating the probability that we, as the human civilization, will attack or invade an inhabited exoplanet.

If you think about Caballero’s idea of extrapolating the human probability of humans attacking alien exoplanets to calculate the likelihood that if 15,785 alien civilizations could exist according to SETI figures, how many would attack us if they were like us isn’t an unreasonable method. Films like Avatar portray how humans might behave when colonizing an alien world to mine its mineral resources. There has been significant discussion about the possibility of mining Ceres and the asteroid belt. We should consider that if hostile aliens exist, they will eye our planet’s resources. Films like Avatar and humans’ treatment of aliens are fiction. 

Invasion statistics decline as civilizations become more advanced

Caballero gets us to think about statistics much closer to home, how humans invade and treat each other. We should be scared of aliens like ourselves, particularly if aliens are like Americans, who Caballero notes hold the record for invading other countries. On a positive note, humanity seems to invade its neighbors less the more evolved it becomes. We can only hope the same is true of future alien encounters.


Caballero looked at the number of countries that invaded others between 1915 and 2022; 51 of the world’s 195 countries had undertaken some type of invasion, with America holding the record. 

Then he calculated the chance of each country launching an attack based on its share of global military spending.

Caballero then multiplied each country’s individual probability of inciting an invasion by the total number of countries on Earth, arriving at the current human likelihood of invasion of an extraterrestrial civilization.


Caballero predicted using the Kardashev scale — a metric that categorizes how evolved society is based on its energy expenditure — that interplanetary travel won’t be achievable for another 259 years if current rates of technological improvement maintain. The current probabilities of humanity invading another inhabited planet, according to this estimate, are 0.028 percent. That probability, however, applies to the current stage of human civilization, according to Caballero, since humans aren’t now capable of interstellar travel.

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Energy consumption estimated by Kardashev scale by Indif under CC BY-SA 3.0

Suppose the frequency of human invasions continues to decline at the same rate as over the last 50 years (an average of minus 1.15 percent per year, according to Caballero’s paper). In that case, the human race will have a 0.0014 percent chance of invading another planet when we become an interstellar, or Type 1, civilization 259 years from now.

From this calculation, Caballero concluded that just 0.22 of the Type 1 civilizations would be hostile to humans if they came into contact with them. According to Caballero, when extraterrestrials that are not yet capable of interplanetary travel, such as modern humans, are included, evil neighbors rise to 4.42.


Caballero admits we don’t know if all of the civilizations in the galaxy are similar to ours. Since we don’t have the technology to go to their planet, a civilization like ours is unlikely to constitute a threat to another.

Caballero said that humanity’s chances of contacting one of these hostile civilizations and subsequently being overrun by them are improbable.

What are the chances of hostile aliens appearing at our doorstep?

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The chances of an extraterrestrial invasion by a hostile alien civilization whose planet we have communicated with are around two orders of magnitude smaller than the chances of a planet-killing asteroid collision. Planet-killing asteroids, such as the one that wiped out the dinosaurs, happen once every 100 million years.


A flawed research paper allows us to rethink the wisdom of trying to contact aliens

Caballero acknowledges that his model has flaws, but his work is an intriguing thinking exercise. The invasion probability is based on a relatively limited period of human history. It involves numerous assumptions about our species’ future evolution. According to Caballero, the model also assumes that alien intelligence will have brain compositions, values, and empathy similar to humans, which may or may not be the case.

Caballero’s research leaves room for worst-case scenarios in which a higher percentage of alien civilizations have less empathy than humans and could have more advanced technology than humans. He could only base his paper using statistics on life as we know it, as we have no idea what other extraterrestrials might think.

Caballero’s research perhaps helps experts in SETI and METI revisit the question of the chances that humans may initiate contact with a hostile alien civilization capable of invading our planet?


More and more academics are applying their intellects to the field of extraterrestrial study. Caballero’s research allows experts to pause to think about whether they should try to contact aliens. Recent research by Irina Romanovskaya proposes that aliens who have escaped catastrophic events in their own worlds may be capable of using floating planets to travel the universe without using starships. Other scholars, such as Harvard Professor Avi Loeb, are betting their professional reputation that we may film a UFO within two years.

Research like this may make you wonder how unfortunate an alien race might have become if they had messaged Earth and a leader like Hitler? Others might argue that there were probably worse human civilizations for aliens to have made first human contact with between 1915 and 2022. Perhaps, based on our human history, it is aliens that should be fearing us and the weapons humans have unleashed on each other.

Callabero’s paper comes to the fore at a time that Elon Musk one day hopes to send over a million colonists to Mars and make humans an interplanetary species.


Feature image credit: Hostile alien attack by Shutterstock.com