In almost every media depiction of aliens, the extra terrestrials are portrayed as creatures that look nothing like humans, and in most cases have to rely on disguises to blend in.
One would chalk this up to a storyteller’s need to differentiate them from us, but it turns out that there are actual scientific – and logical – reasons why aliens will look vastly different from humans:
1. Difference in gravity
Gravity plays a huge part in how living beings in a planet look. It limits the size of land animals and influences many creatures to develop specific features in order to adapt. For instance, land animals have developed complex skeletal systems to offset the force of gravity, which marine creatures don’t have to worry about.
2. They’re not carbon-based
All living things on Earth are carbon-based, mainly because carbon is very good at bonding with other atoms, stable, and can form complex biological molecules. But it’s not the only element that can do so.
3. Participant evolution
Participant evolution is when living creatures use technology to modify and adapt their bodies instead of waiting for nature to take its course. It’s already happening here on Earth in subtle ways (surgery to enhance one’s looks, for example). What more for creatures who have been around longer?
4. The power of random chance
Lastly, we can never rule out the power of random chance. Would humans have managed to evolve the way we look like right now if dinosaurs didn’t go extinct? Even if there’s a planet out there that had human-like creatures, a single random factor could result in their evolutionary journey taking a different path.