What Would Aliens Actually Look Like?

What Would Alien Life on Other Planets Look Like?

Author Arthur C. Clarke famously said that “two possibilities exist: Either we’re alone in the universe or we’re not. Both are equally terrifying.” Today, as terrifying as the concept may be, the latter is almost certainly true – with more and more scientists, thinkers and philosophers agreeing that extra-terrestrial life is more than likely ‘out there’. But what would aliens actually look like?

Unfortunately for sci-fi buffs, it’s safe to say that life on other planets probably doesn’t resemble the grey humanoid creatures with over-sized heads that populate (and often terrorize) science fiction movies and classic abduction stories. Or, at least, aliens are just as unlikely to look like that as they are to look like anything else. However, there is increasing opinion that prospective lifeforms might not look all that alien at all.

In 2017, a team of Oxford University biologists argued that life on other planets would evolve the same way it does on Earth – and that aliens would most likely be carbon-based like us, due to the abundance of carbon in the universe. It’s the fourth most common element there is and, while hydrogen and helium combine to make up 98% of the entire universe’s baryonic matter, the team still collars carbon as the most likely candidate for life.

But, the approach proposes that alien life shares the same building blocks as our own, when it’s also possible that aliens would be composed of other elements entirely. Even on Earth, there are bacteria groups called extremophiles capable of living in extreme environments that are uninhabitable for everything else – from alkaline lakes to volcanic springs. So, if relatively ‘regular’ bacteria can live in such conditions on Earth, it’s surely possible that an alien society could live on planets composed of, well, anything. Silicon has been put forward as a viable option by some, because it’s a) a solid at room temperature, and b) it forms similar structural bonds to carbon. Ultimately, when dealing with something we’re not yet scientifically sure of, the possibilities mount up and up. Which, obviously, makes determining the exact physical attributes of aliens more than a little difficult.

Ask an astrobiologist, and they’d probably point you toward single-celled organisms. Despite our far-flung searches for similar worlds, there just aren’t that many planets like our own. Most are harsh and unforgiving places, even the ones found in apparently habitable zones… so, the likelihood of evolution happening as we understand it, is low. Theories like this kick against our pop culture stereotypes but are some of the most popular around – painting aliens as little more than microscopic beings found in almost unimaginably extreme conditions and locations.

For the sake of argument, though, let’s say these single-celled organisms did manage to band together. In the infinite reaches of time and space, evolution would eventually (or even inevitably) begin. And, natural selection would shape the emergence of life on any planet just as it did here. So, after evolving to create sentient life, are there any universal rules regarding physical appearance and biology?

In 2018, after extensive research, theoretical physicist Michio Kaku determined that there were at least three basic requirements. The first is that aliens must have some form of eyeball, stereo vision or at least visual awareness to track distance, successfully hunt, and effectively defend themselves. More broadly speaking, others have suggested that an alien species would certainly need some sort of sensory connection to survive.

Next, Kaku claims that aliens would require a grasping appendage, again for hunting but also for creating tools (and using them). In humans, we think of our opposable thumbs as being a major reason for why we’ve evolved as we have. But, the alien equivalent needn’t look like our arm-to-hand-to-thumb set up. Sci-fi sometimes shows us aliens with tentacles protruding from all parts of their bodies, but the basic idea isn’t that different. As long as the body develops a means of controlling what’s immediately around it – for movement, security and feeding – as well as housing whatever internal organs it carries, then its chances of survival are much higher.

Finally, Kaku suggests that an alien lifeform must also have developed a type of communication or language. Of course, humans have created various communication methods over time, but there’s no real reason to believe that aliens would speak or write to each other in the same ways as we do. In fact, the unprecedented language barrier is one of the biggest hurdles for anyone predicting what first contact with an alien race would be like… because, would we even know that it was happening?

Interestingly, Michio Kaku has himself identified the octopus as matching most of his alien criteria – minus the language. While Kaku is in no way suggesting that octopuses are aliens, if we follow his rules then it’s not too difficult to imagine an extra-terrestrial octopod creature. That said, it’s also pretty easy to picture a blobbish mass constructed entirely differently. While we have zero proof of what sentient, complex aliens would physically look like, we at least have some idea of how they might appear – with probable eyes of some kind, appendages for sensory stimulation and physical movement, and a body sturdy enough to encase essential organs.

But, to appropriately bring us all ‘back down to Earth’, the various predictions in no way better our chances of actually finding alien life. It took almost 4 billion of Earth’s 4.5-billion-year history for single-celled organisms to even begin to develop into multicellular beings. If similar timelines are also applicable on other life-sustaining planets, then our chances of actually encountering an advanced alien race seem slim… Until we develop tech powerful enough to scour whole galaxies and pinpoint far-off planets in speeds currently considered physically impossible. Then, we might have a chance.

If and when we do finally cross paths with an extra-terrestrial existence, there are a couple of schools of thought. One is that we’d be completely unaware of crossing paths with anything at all, so different and unrecognisable would the alien life be to our own. But, the other says we’d be able to apply at least basic understanding to whatever it was we’d discovered. In which case, it’s most likely that we’d find some form of plant-life – rather than mammalian or complex beings – given that plants are the predominant form on Earth itself.

Perhaps retired astronaut, Jeff Hoffman, puts it best. Speaking to National Geographic in 2018, he mused that if we ever did find life on another planet, then “it’s probably going to be very simple life”. Yes, it goes against the script of almost every sci-fi story ever written, but such a discovery would still represent a fundamental turning point in human history.