Thoughts on alien life

Science fiction movies and television shows often portray aliens as remarkably humanoid. This is obviously a matter of convenience since most of the actors available to portray aliens are themselves typically humanoid. But it's become somewhat common for people to critique these shows for a perceived lack of imagination in the design of the aliens. The objection is that aliens would look completely different, dare I say "alien". But is this really the case? Would aliens really look so terribly different from us?

I want to be clear that I am specifically talking about intelligent aliens. We know from our own animal kingdom that life can take on a huge variety of bizarre forms. So there's every reason to think alien creatures would be every bit as diverse and bizarre as what we see here.

But intelligent life is another story all together. There have been many millions of species on this planet since life began. Yet, as far as we know, only one has evolved into intelligent life. Why is that? Convergent evolution clearly demonstrates that unrelated species can independently evolve similar traits. Insects, birds, and bats, for example, all independently evolved flight because flight offered some survival advantage. Intelligence has undoubtedly given us a tremendous survival advantage. So why are we the only species to have it?

I submit that physiology plays a role in the answer to that question. One of the keys to advancing intelligence is the use of tools. This requires a degree of dexterity not seen in many species. Right off the bat, we are limited to creatures that are accustomed to grappling things. This means mainly arboreal or other climbing creatures. Appendages suited for gripping limbs or ledges will be equally suited for gripping sticks, rocks, and more advanced tools. Whereas hooves, wings, and paws are poorly suited for tool use. So horses, falcons, and tigers are unlikely to begin using spears.

A tree or cliff dwelling creature that for some reason decides to begin living on flat ground will also find itself with spare limbs. Forelimbs once essential for gripping the next branch or crag would now be free to carry any number of tools or supplies while leaving the hind limbs free to move the creature about the landscape. This is important since a tool is of little use if you have to set it down every time you move.

Some may argue that tentacles could also allow tool use. But I think this is unlikely. Tentacles have never evolved on land. This is probably due to some physiological limit of the mechanism. So while tentacles are undoubtedly useful and dextrous in their environment, it is their environment that is the problem. Advanced technology, and the intelligent life that co-dependently evolves with it, cannot arise in an aquatic world. You can't smelt ore, harness fire, or build electronics underwater. An aquatic species might possibly advance a ways. But it would be limited to stone age technology. That may or may not be sufficient to qualify as intelligent. But it is certainly not sufficient to communicate with spacefaring species.

Even an amphibious species would be rather unlikely to gain intelligence. Use of fire is a fundamental first step on the road to intelligence. An amphibious species is highly unlikely to develop an affinity for fire. Their need to stay moist is directly at odds with fire's tendency to dry things out. Amphibious creatures don't tend to live in areas where it gets cold enough to require fire for warmth since such cold would make it difficult to maintain the moisture of an amphibian's skin. Without fire a species is again limited to the stone age.

So it seems logically that any intelligent species would have to be terrestrial in origin. But there are still deductions we can make to further define the characteristics of an intelligent species. There must be a minimum size to any intelligent creature. It takes a certain amount of brain capacity to be intelligent. This means there must be a minimum size body to support that minimum size brain. But it is entirely unclear just how large a species must be before the brain reaches the critical mass for sentience. Sentient mice are certainly out of the question. Sentient dogs? Who knows?

There is probably even be an upper limit to the size of an intelligent species. Beyond a certain size, what tools can a species build? Dinosaurs could never have woven cloth much less developed microchips. They could never have ground lenses to make telescopes to examine the stars. Just how big can a species get before the fine details of technology escape its grasp?

Certainly there is room for a great deal of diversity. Species could have more senses, fewer senses, different numbers of sensory organs, more limbs, any number of variations. But I really don't see any logical support for the idea that intelligent aliens would look vastly different from us. There are real limits on the growth of intelligence. Limits that apparently exclude all but one species out of millions. If there were a broad range of traits that allowed for intelligence to flourish then we would surely see more intelligent species on Earth. Since we don't see a wide variety of intelligent life here on Earth there's no reason to suspect we'd see a wide range of intelligent life elsewhere. So there's no reason for writers to create truly bizarre creatures for their shows.