Sci-fi films often portray aliens as basically human-sized. This assumption might be reasonably accurate, given a loose interpretation of what human-sized means.
A smuggler, a Wookie, and two Jedi meetup at the bar. Disney - Lucas Films Limited
Approx. 1400 words; 6 minutes read time
The Mos Eisley cantina in the original Star Wars is my favorite scene in any film ever. Ever. I love it because here we first see how diverse this fictional universe actually is. All manner of creatures co-exist, and most seem relatively at ease around one another, despite their apparent differences. But as diverse as the beings of Star Wars are, they are all about the same size. Sure there are big ones, like eight-foot-tall Chewbacca the Wookie and small ones like the three-foot-tall Jawas. Generally, though, the sentient creatures in Star Wars are within the size extremes of humans. But this need not be a biological expectation.
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First things first: there are myriad implausibilities in Star Wars. This article is not another attempt at shooting holes in the logic of everyone's favorite space franchise. That's been done countless times already. No, I am curious if something about intelligent life mandates it to be about the same size as us. The cantina scene is simply a classic example of alien portrayals, giving a foundation to explore this intriguing question.
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To begin addressing what size we can expect aliens to be, we have to make a big assumption: carbon-based life. There are some compelling theories out there proposing alternative lifeforms, including silicon-based. But these alternative chemistries open up a universe full of possible body plans and sizes. No, let's stick to carbon. Star Wars characters are mostly portrayed as carbon-based anyway. And we know how carbon-based life behaves in our real world. So assuming carbon will help keep this as simple as possible (and will also keep this story under 1500 words).
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Biologically speaking, there doesn't seem to be any reason intelligent life needs to be human-sized. Neuroscientists have studied for decades how and why humans appear to be smarter than all other animals on Earth. Factors such as brain size and neurological makeup do not alone determine this intelligence. For example, male human brains are larger than female brains, but there is no difference between male and female IQs. And elephants have larger brains than humans, but no evidence supports that they are smarter than us overall. And small minds can be super bright too; ravens show an incredible intelligence, despite having tiny "bird" brains.
Intelligence is challenging to pin down in terms of how and why, even after years of study. Scientists have concluded that many factors beyond size and neurology dictate smarts, and these can come together in vastly different ways depending on the species and its environment. So at least biologically speaking, intelligent sentient life need not be the same size as us.
Given what we know about brains and intelligence on Earth, this is a qualified “no” to the cantina scene. But there’s more to this question than biology alone.
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There are planetary-scale factors involved in body size: gravity and environment, being the most influential. Life here on Earth has evolved as it has because of the size and position of our planet as well as it's geology and atmosphere. Species that are fit for these conditions go on to survive, and successfully reproduce and prosper. The same will be valid for species that evolve elsewhere, potentially under vastly different circumstances.
Biological features fit for Earth might not be so good on another planet, opening up all kinds of possibilities for body size and other attributes. Gravity, in particular, can change things drastically: the more of it, the smaller we expect creatures to be. Bigger body plans need stronger bones, more muscle mass, and increased metabolic capacity. As gravity increases (as planets get bigger), so do these requirements. Smaller creatures are less affected by gravity and would have a competitive advantage on big worlds. So it stands to reason that more massive planets will favor smaller creatures, and lesser planets will support larger ones.
The environment, too, affects body size by limiting available resources. Smaller planets will have fewer resources restricting how many larger creatures they can sustain. Here on Earth, smaller animals often occur in higher numbers than bigger ones for the same reason. There are 7.5 billion humans on Earth, but there are ten quintillion insects, for example. And generally speaking, the total numbers of any-sized creatures will be fewer on smaller planets and greater on larger ones.
In many ways, planet-size dictates these two competing forces - gravity and environment. And, in turn, these influence the size of a world's creatures. Evolutionary biologists study these and related factors to understand how they affect the evolution of life on Earth. And the algorithms used to predict how life came to be here can be applied to other planets.
Recently, a study was conducted using Bayesian statistics or "game theory" to hypothesize what the size of intelligent aliens would be on average. According to this research, there is a 26% chance an alien would be human-sized or smaller (0-100 kg; 0-220 lbs), and a 74% chance it would be larger (100-100,000 kg; 220-220,500 lbs). These results suggest that the median size for an intelligent alien would be about 310 kg (684 lbs) - over four times bigger than an average human (70 kg; 140 lbs).
This study seems to support the cantina scenario loosely. The median size for an alien is roughly that of a large grizzly bear - and not far off from the mighty Chewbacca. But the results don't preclude smaller or larger aliens; they only support that, statistically, aliens will be bigger than humans on average. The little guys - and massive guys - could exist too. So given enough time, all manner of creatures could still make it to the galactic watering hole, human-sized and otherwise.
But not so fast, space cowboys. There's one more challenge. How do these creatures leave their home worlds and get to the cantina at all?
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It's one thing to evolve into an intelligent being. Given the billions upon billions of planets, everything from bird-sized brainiacs to whale-sized scholars might exist. But this doesn't mean all could manage to leave their home planet in the first place. Yes, the universe might be teeming with eager bar-goers, but many might not have a ride to the pub.
Disney - Lucas films Limited
Tiny Babu Frik from Star Wars IX: The Rise of Skywalker is a species that might not make it to the party. While Frik and his kind perhaps evolved on some super-Earth favoring their small stature, the extreme gravity there might keep them trapped at home - it would be too energy demanding to escape the planet's gravitational grip. As for a giant genius species of some kind? Such a being could have evolved on a smaller world with less gravity, but with limited resources. So limited that the big fellas would run out of stuff before they became interstellar and headed off to the bar.
These limits on both small and large body sizes might weed out all but those lifeforms in the vicinity of human-sized beings. This, of course, brings us back to a qualified "yes" in support of the Mos Eisley cantina scenario.
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Disney - Lucas films Limited
I find this outcome somewhat surprising. Think about it - the cantina scene, and the Star Wars universe overall, were designed to accommodate human actors on human sets. This was not an effort to mirror potential reality in a galaxy far away. But at least from a superficial viewpoint, it does just that - a case of art portraying reality in a rather unexpected way. Yes, it's not a wrong assumption to think aliens will be at least close in size to us.
Until next time. Science. Fiction. Create.
JRC