I Am Not Groot: Alien's probably won't look like us

Exoplanets are planets that orbit a star outside the solar system and there are a plethora of them in the universe. Some of these reside in the so-called “goldilocks zone,” or the region around a star where water on the surface can be liquid and can therefore sustain life. There are now 3400 confirmed exoplanets thanks to the National Aeronautics and Space Administration (NASA) missions like Kepler.

With so many exoplanets out there able to sustain life, it makes you wonder: what would that life look like? According to Hollywood, aliens would look a lot like humans. From Spock of Star Trek to Groot of Guardians of the Galaxy, science fiction movies tend to portray aliens largely as humanoid in nature. A more recent film, Arrival, strayed from the predictable and stereotypical portrayal of alien life, creating an otherworldly creature resembling a cross between a giant hand and a squid. So, which depiction is more accurate? If alien beings evolved on one of these earth-like exoplanets, would they look like us?

Although there is no way to definitively say what aliens might look like aside from actually finding life on another planet, some believe that there is a level of predictability to evolution that would cause them to look similar to humans. This predictability can be seen in convergent evolution, or the process by which organisms that are not closely related independently evolve similar structures. This recurrence is often a result of natural selection and a limited number of solutions to a survival problem. A classic example of convergence is the evolution of wings in three separate lineages: insects, reptiles and mammals. These organisms evolved a similar trait in order to diversify into similar ecological niches, or positions a species has in their environment. Convergent evolution such as this is much more frequent than biologists originally thought, leading some to think that evolution is deterministic and that we could therefore predict that aliens would look very similar to us.

But there are many problems that this argument is not addressing. First off, this reasoning assumes that these Earth-like planets would be identical to our Earth. Most likely these planets would differ from our earth, as shown by the fifteen confirmed ‘habitable’ Kepler planets that vary in amount of sunlight, temperature, size and atmospheric density.  These differences would pose unique challenges for organisms of those planets to adapt to, leading to different body structures.

Even assuming that there is another planet identical to Earth, there are still many variables of chance that would cause the alien species to look quite different. Another significant selection force is genetic drift: chance events that alter the allele frequency of a population. Motoo Kimura’s neutral theory argues that more mutations become characteristic of a population due to genetic drift than advantageous mutations due to natural selection. A well known example of this is the asteroid that drove dinosaurs to extinction. While dinosaurs roamed the Earth, mammals were small and adapted to hide from and evade large predators. Once the dinosaurs were wiped out by the asteroid, however, ecological space was opened up and mammals diversified into these newly created ‘niches’. Other large scale events, such as disease, typhoons, or earthquakes, could cause a significant change or departure in an alien population, creating a species that is unique from humans. 

The most probable answer to the question of if aliens would look like humans is no, they would most likely not. Although there are small ways in which evolution can be predictable, there is too much influence of chance. Chance events and environmental differences would lead to species altogether unique from what we see here on Earth. So, if you want to see an accurate depiction of what aliens would look like I would trust Arrival over Guardians of the Galaxy.


Samantha Pierce is a campus correspondent for The Daily Campus. She can be reached via email at samantha.pierce@uconn.edu.