Throughout science fiction books, comics, and movies we have been treated to a never ending menagerie of alien beings taking a vast number of forms. In the old days budget constraints for TV and films meant that usually aliens looked at least a little, well, human. In more modern times computer effects have made things a little more bizarre, but still mostly aliens are portrayed as at least something we can understand or relate to at least on a basic level. It is all indicative of our intense curiosity as to what alien life, and in this case intelligent spacefaring life, would actually look like. If a spaceship came down tomorrow and opened up a door, what would step out? Would it be something like us, or something beyond anything we have ever imagined? It is a question we have no way to answer, but there has been quite a lot of speculation on the appearance of aliens, and here we will take a look.
So, if we were to meet aliens what could we realistically expect them to physically look like? What form would they take and how would they interact with the world around them? The answers to this seem to be as varied as the people who ponder the question, and there are several ways that the discussion can head. On one side we have the idea that since they have evolved from a different lifeform and on a completely different alien world, they would look nothing like us, and could be beyond what we can even imagine. There have been all manner of ideas on this, ranging from that they might not be even carbon based to that they don’t have DNA, live in an invisible wavelength we can’t see, or that we might not even recognize them as life within our own definition of the term at all. One science fiction author by the name of Aaron Rosenberg explains of this idea:
Living beings evolve in response to their environment. We grew opposable thumbs so we could better grasp objects. Monkeys developed prehensile tails for the same reason. We have eyes because light breaks down into the visible end of the electromagnetic spectrum here. But if we had occurred on a completely different world, with different temperatures and topography and flora and fauna, we would have evolved differently. And if that other world had a completely different chemical composition, so would we. All life on Earth is carbon-based, but that wouldn’t be the case elsewhere. Life forms could be silicon-based or iron-based or anything else at all. They could have any number of arms and legs—or none at all.
Perhaps life on other planets evolved without physical form or with no fixed form—perhaps there are aliens who are nothing more than sentient clouds, or who have mutable bodies that can alter to suit the needs of the moment. Maybe they can sail through space unaided, and use stellar radiation for a food source and a sensory array, detecting changes in the radiation the same way bats detect sound waves. Who needs eyes and ears when your entire being resonates? Who needs a distinct brain when your consciousness is spread throughout just like our nerve endings are with us? Why have skin when your form is held together by electrostatic shock and mental control, and can condense or expand at will?
There are plenty of creatures here on Earth that are so astoundingly different from us that we can barely comprehend them. Try watching an octopus pull itself through a tiny crack in a glass tank sometime, or examine a tobacco hornworm, or look at a praying mantis up close. Then think about how small our planet is compared with the universe as a whole—it’s like finding the weirdest shaped M&M in the bag, and then realizing that you’re in an entire candy store filled with literally thousands of other kinds of candy, most of which you’ve never even heard of before. A real alien would be so far from anything we’ve ever imagined that we would barely be able to comprehend its existence. And we would seem just as completely, bafflingly bizarre to it.
The thrust of the idea here is that aliens would be, well, completely alien to us, perhaps even incomprehensibly so, and that all bets are off when trying to expect how they would appear to us. One only needs to look at some of the incredibly different and even seemingly alien forms of life on our own planet to know that something from another world could be vastly different from us. However, we are talking about intelligent life here that has created a civilization and reached out across the stars to meet us, and so the opposite side of this argument is that, although they would certainly be quite different from us, there are certain constants that we could expect that would match up with us as well, and we can perhaps make an educated guess as to what they might be like.
There have been many suggestions for certain criteria that any intelligent, space-faring race would likely conform to, boxes to tick, so to speak. For one, although they would be coming from far, far away, they would nevertheless follow the same laws of physics and chemistry as us, as that is a constant across the universe, at least this one. Prof Peter Ward, a paleontologist at the University of Washington, explains of this, “On any planet in the Universe the laws of physics and chemistry will still be the same as here. There’s only a limited number of ways to beat physics.” One of the other very basic things we could expect from an alien being is that it would likely be bilaterally symmetrical, that is with one half mirroring the other to at least some extent. Every form of life on Earth is this way, and even inanimate objects such as crystals, and even whole galaxies, so following this seemingly universal constant they would probably be at least symmetrical to a degree.
Because of the universal physics involved, there would also probably be some broad rules of ecology in place that they would have to have overcome in specific ways. For instance, they would need a way of gaining energy, of hunting and eating, as well as sensory organs to perceive the world around them, and they would have to obey the rules of gravity, ambient density, and having a source of energy. They would need some way to reproduce and propagate their species and they would have to out compete other species in the same environment to last long. In other words, no matter where the aliens are from, they would basically have to overcome the same basic physical and evolutionary constraints as us. There are only so many ways to move around or get food, look at how similar some swimming or flying species are on Earth, no matter how genetically different, think bats and birds or sharks and dolphins. Some ways just work better, and evolution would have weeded out the inefficient ones in the face of competition from other species. In many opinions, these hypothetical aliens also would have probably evolved from predators, meaning they would probably have stereoscopic vision, which allows the judgement of distance, meaning more than one eye on the front of the head, and they would likely be mobile rather than a sedentary plant-like species. They would have also likely would have had to become the dominant lifeform on their world, so probably not microscopic or unduly frail. The renowned theoretical physicist Michio Kaku has said of this:
In all likelihood, intelligent aliens in space will have descended from predators that hunted for their food. This does not necessarily mean that they will be aggressive, but it does mean that their ancestors long ago might have been predators. We may be well served to be cautious.
Another constant they would probably exhibit is that they would have something that passes for a brain, and that it would be encased in some sort of protective shell, be that a skull, exoskeleton, or whatever, and this brain would also probably be held high off the ground. The aliens would need some way to breathe, and some form of locomotion that would have to have at least been fast enough to have allowed them to hunt and survive on their own planet to become an evolved species. These would probably come in the form of some sort of legs if the alien is land-based, and there would be some sort of covering over the body that we could recognize as “skin” of a sort. Harry E. Keller, a chemistry professor at Northeastern University has spoken of these two points with Popular Mechanics, saying:
Legs? Most certainly. Other means of locomotion will be relatively slow and be relegated to armored animals and of those living in holes. Neither of these lifestyles will lead naturally to greater intelligence. How many legs? In our case, we adapted the forelegs for manipulation from animals with four legs. No land animals with endoskeletons have more legs. The implication is that aliens with two legs are more likely than those with four.
Fur? Hair? Feathers? Scales? Something else truly alien? The skin covering could be anything that makes sense. Real feathers are not so likely. Because feathers are used for flight, brains will be small. Scales are unlikely because they are particularly well-adapted for ectotherms, although a scaly sort of skin might be possible. Fur versus hair is hard to sort out because of my inherent bias. Fur has good reasons for being that are not related to intelligence. If furry, our aliens probably have short fur.
In order to make tools and manipulate their technology, they would have to have evolved some sort of appendages with fine movement control. This doesn’t necessarily have to be fingers and a thumb like we have, but some grasping appendages of some sort, something akin to what we would recognize as their version of digits. These appendages would also likely be freed up for use, meaning they might be recognizably bipedal. They would also need some sort of analog of sensory organs to perceive their surroundings, such as eyes, nose, and ears, as well as some way to procure energy, in short, a mouth, probably near the eyes where they can see what they are trying to eat. As for these eyes, there would probably be at least two eyes facing forward, for that stereoscopic vision we talked about earlier, and there aren’t a whole lot of other viable ways to achieve that. The eyes would likely be recessed, and there would likely be some way to cover and protect them. These eyes would also probably be close to the brain, so as to minimize the time of signal transmission. They would be attuned to the spectrum of their own sun, and may look very different from our own eyes, but they would likely be at least recognizable as such. In addition to all of this, they would need a way to produce sounds or signals for some form of communication and crucially, language, as any spacefaring society would need a way to convey complex information to each other, although that potentially holds therein its own problems. Some other theories of what intelligent civilizations of aliens would need even go so far as to say that they would likely not have evolved underwater because they would need to have developed a mastery of fire in order to progress to that stage.
To sum it all up, when faced with the same physics, physical requirements for survival, evolutionary constraints, and criteria for developing tools and technology, in this idea, with any aliens who flew starcraft to Earth we could probably expect to see land based, symmetrical beings with recognizable sensory organs, limbs, and other features with some analog to what we know of, and so would not be as completely, absurdly outlandish as others would have us believe. They would most certainly not look like humans, and of course depending on the gravity and specifics of their atmosphere and world at large they would look very different in various ways, but the point here is that they perhaps they would not be so mind-bogglingly, impossibly and vastly different from life as we know it and understand it to be. However, this is all assuming they are even from this dimension at all, because if they were from a completely different universe, possibly even with different laws of physics, then we can probably throw all of this out the window.
Of course, this is all assuming that the aliens are even organic lifeforms at all. There has in recent years been increasing speculation that space-going aliens that make it to Earth might not be biological organisms at all, but rather very advanced robots. These machines might have been sent here by their creators or might even be a self-replicating race of robots that usurped their biological makers, with their originators perhaps even distant, long gone prehistoric faded memories for them. It makes sense, as it would be the next step up in evolution from the confines of biology, and robots would be perfect for the rigors of space and the vast distances involved with travelling to other worlds. However, if they were robotic, then all bets would probably be off as far as appearances go, and they might display design choices that truly are beyond comprehension, although they would still have to follow our same laws of physics. Professor Susan Schneider from the University of Connecticut and the Institute for Advanced Studies at Princeton thinks that such robotic alien civilizations could feasibly be billions of years old, and has said:
I do not believe that most advanced alien civilizations will be biological. The most sophisticated civilizations will be post-biological, forms of artificial intelligence or alien superintelligence. Other civilizations may be vastly older than us – earthlings are galactic babies. All lines of evidence converge on the conclusion that the maximum age of extraterrestrial intelligence would be billions of years, specifically ranges from 1.7 billion to 8 billion years.
In the end, it is hard to really get a handle on how intelligent spacefaring aliens would look, as we really only have one example to compare them to- us. All of our ideas on extraterrestrial life and how to find it revolves around our basic presumption that they would meet the criteria for life as we know it, but there is of course the possibility that this is not true at all. Indeed, there is a vocal contingent that thinks the reason we have not found alien life out in the universe despite all of our efforts is that we are looking in the wrong places and in the wrong way. Maybe our own definition of life is the rarity rather than the norm, and perhaps we have to change our perceptions. Only time will tell.
In the meantime, we are left to speculate. What will intelligent alien life from another planet look like if we ever make that first contact? Would they look in some way like us and life as we know it, or would it be incomprehensibly and unfathomably alien? Would we even be able to recognize it as life at all? We can guess, extrapolate, speculate, and debate it all we want, but the only way it seems we are ever going to get the real answer is when that ship lands and they step, slither, or float out into the light.