Getting to know the aliens
If there is one theme that pervades the very concept of “space” in the public mind, it is the assumed ubiquity of alien life. This probably tells us a lot more about the way that human beings perceive the Universe through a lens of assumptions and evolutionarily-implanted deep instincts then anything about the nature of life beyond Earth.
Although it may seem quaint and rather naive today, just a few centuries ago many learned Europeans took it for granted that the Moon and the planets were doubtless populated by human beings of some type. The “proof” of this paradigm was often theological: God would not possibly waste His valuable time creating uninhabited celestial bodies, after all!
As astronomy progressed, the worlds of the Solar System slowly began to reveal themselves as quite unEarthly indeed, though the assumption of alien (and for all practical purposes, human) intelligent inhabitants possessed its own considerable inertia, resisting mounting scientific evidence with an interesting tenacity. The men of Mars became small and green, with ever-increasing lung capacities and tolerance for cold weather as the planet’s true conditions became apparent over time. Venusians remained mermaids and/or jungle dwellers until the early 60s, since that world’s dense sulfurous cloud cover yielded few clues about the surface below to ground-based astronomers.
Today, robotic exploration of the Solar System has decisively laid to rest the idea that men (little & green or otherwise) evolved anywhere else in our neighborhood besides Earth, and one under-appreciated revelation of molecular biology is that the number of possible DNA combinations exceeds the total number of protons (yes, protons) in the observable Universe by many orders of magnitude. Therefore, it’s a very safe bet indeed that the human form (and quite likely that of virtually all other types of terrestrial multicellular life) is unique to Earth, and this conclusion is widely accepted…right?
Nope. Not even close. Why?
It is not too surprising that the general public still thinks that alien intelligent beings will look like people with bizarre makeup jobs or hairstyles, or in the most extreme and apparently horrific cases possess an extra arm, leg or eye. Perhaps ‘They’ might not even be mammalian; humanoid reptiles seem to be the traditional way-out possibility (horror of horrors; shoot ’em!!!) The UFO mythos that arose after the end of World War II as an artifact of profound technological shock certainly has some responsibility for this fundamental perceptual bias, and even today keeps little green men and their elongated, emaciated cousins–all sensibly equipped with heads, torsos, two eyes, two arms, and two legs, of course–ensconced in popular culture. The entertainment industry completes and widely perpetuates the bias. After all, movie and television producers have limited budgets and resources, and one can only modify an actor’s appearance so far before he or she loses sex appeal, the ability to communicate emotions and intentions, or even the ability to move. None of that is particularly helpful for box-office appeal, so movie aliens almost always look quite human indeed.
What is considerably more surprising is the fact that a significant number of biologists and other scientists periodically produce arguments that at least the basic attributes of the human form are not just one of many optimal designs for intelligent life, but perhaps the inevitable and only one. Some even speculate that had the Cretaceous extinction event not occurred, a dinosaurian humanoid intelligence would have evolved in lieu of Man. (Fortunately for “dinosapiens”, the lowly primates in this scenario would be completely incapable of shooting them. Unfortunately for the primates, dinopeople very well might consider them tasty.)
Clearly, there is more than mere human chauvinism or lack of imagination involved here.
It is easy to explain our unconscious assumption that life must be widespread in the Universe. Life is ubiquitous here on Earth, and we knew practically nothing of other worlds until quite recently in our history. Countless science fiction movies and television shows have depicted “lifeless” planets with sparse vegetation (!); at the very least, we expect an ecosystem as rich and diverse as our own! But why do we always expect to find humanoid, albeit funny-looking, aliens as well, even though we really should know better, even to the point of scientific rationalization of the idea?
The answer lies in the fact that we evolved as highly social, clannish, and competitive animals. For perhaps 95% of our history as a species we lived in small, isolated groups widely scattered around the face of the planet. Contact between these tribes was infrequent, minimal, always competitive, often violent. Whenever a clan migrated to a new place, they would inevitably meet one or more Others who did not resemble them, communicate like them, or even smell like them. These encounters were always risky. The strangeness of the Other became a cue for caution, since competition for food and territory so often led to conflict.
All of our ancestors met aliens–but the aliens were always human. It’s difficult to overcome a complex set of perceptual biases perhaps 200,000 or more years old.
Our assumptions have served us well in countless ways, but as we stand on the threshold of the Universe we must constantly remind ourselves that what we see is modulated by who we are. We may find intelligent aliens someday; if we do, they will not resemble us in any particular, much less physically, and they will have their own biases to overcome as well. We will find extraterrestrial life someday; we may not recognize it as such at first. It may be a mistaken assumption that even DNA is as universal as the human form was once (is still?) assumed to be. It may well be a presumption that we even understand the limits of organic chemistry itself, and clues to that may be waiting for us close at hand on the surface of Titan.
With breathtaking speed when considered over the span of humanity’s existence we are finally leaving our cradle, this delicate blue and white world of wonders that has been our only frame of reference since long before we first noticed that distant pale disc that changed shape with regularity, much less those odd points of light in the night sky. Yet as we leave, as we continue the often humbling maturation process of learning, it is wise to remember that we also have much to unlearn.
beyond the cradle 
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