Terrestrial life, extinct and past; or alive and present is amazingly diverse – in appearance anyway, but also in the environments they inhabit and the abilities they have to survive and thrive. But under the skin, our fundamental biochemistry, be you T-Rex, or be you a maple tree, or be you a bacteria, or be you, you, well you’re all as closely related as makes no odds. Extraterrestrial life will also be amazingly diverse – in appearance. However, the fundamental biochemistry that makes them, them, might be equally diverse relative to what makes you, you.
Traditional Hollywood fare, when it comes to envisioning aliens, tends to take the cost-friendly option and place actors in strange looking, but humanoid form costumes and associated make-up. Or, forget the costumes, maybe they just give the actors pointed ears or paint a few dots on them or wrinkle their noses! The question remains, will real, as opposed to Hollywood’s version of intelligent alien beings be humanoid, or something quite less than humanoid? At a more fundamental level, will the aliens, regardless of appearance, be composed of the exact same sorts of bio-friendly bio-elements and bio-molecules as we (we being terrestrial life forms collectively) are? Will our neighbours among the stars resemble life-as-we-know-it or life-not-as-we-know-it? And what really counts as life-not-as-we-know-it? Is it appearance, environmental habitat, abilities or is it chemistry?
Appearance: This isn't so much an exercise as in a general ‘design an alien life form’ but what might a technologically advanced intelligent life form look like – inevitably humanoid, or perhaps not? Let’s start with the general humanoid form as likely – or maybe not. If you were designing an intelligent alien being from scratch, say our technological equals or better, what would you have to include?
Well, you’ll need sensory organs. No life form that has developed technology will be blind and/or deaf; touch has obvious survival value, as does taste and smell, but these are secondary to vision and hearing. You don’t have to have external ears to hear though, so the one essential feature will be eyes. Eyes have evolved independently many times in terrestrial biology, so vision is as close to essential as makes no odds. The eyes could be unusual in that they might have evolved to detect different areas of the electromagnetic spectrum than just visible light. The one other point about vision is that the higher up the eyes are placed the better in order to see farther. I mean if your eyes were located at the tips of your big toes you’d be visually handicapped relative to a being with eyes much higher up. Two eyes are better than one in order to achieve stereoscopic vision, and give some redundancy protection. Compound eyes work too, as any fly adequately demonstrates, but in order to see the really fine print, compound eyes are lacking.
You need to get around, so that means some form of locomotion equipment. Fins and flippers are okay if you’re a water creature, but spending your life in water isn't conducive to developing technology. Scratch fins and flippers. Okay, so I assume you’re land-based, at least some of the time. One locomotion appendage will get you around if you hop, but two, four, six, or eight, etc. work too, and again, provide some redundancy backup. An odd number of limbs isn't unknown, say a starfish; and some four footed animals can survive even with the loss of a limb. You might think that too many limbs might be selected against since you’d think the extra neuron power need for coordination would reach the point of diminishing returns. However, centipedes/millipedes, etc. put the lie to that. The number of limbs (tentacles are cool too) aren't critical; what’s critical, if you’re to develop technology, is that you have to have appendages (even tentacles) that can manipulate the objects in your environment.
Now scallops can move about without having limbs, but it’s hard to visualize a scallop type life form developing technology, primarily because that form of locomotion only tends to be effective in a liquid environment, and a liquid environment isn't conducive to achieving high technology.
If you have technology then it’s fairly obvious you have the ability to manipulate objects with some sort of appendage(s). The minimum required is one. Humans who have lost the use of a hand can still function and manipulate objects with the other. A tail might suffice. Then there are tentacles!
You probably need a central processing unit (CPU) – a brain of some sort – but it wouldn't of necessity have to be up top.
Then there’s the topic of whether you have internal or external support – some structure to support the innards or insides of a life form. Housing support could come in the form of a simple sack – an external membrane holding in the innards, like a cellular wall. Or, that external wall could be tougher, like an external hard shell, say like a clam, snail or insect tends to have. Or, even though every life form has to have some sort of external ‘skin’, the actual job of keeping the innards, inside could be more the function of an internal skeleton, the kind vertebrates like us have and to which the bits and pieces are housed in and supported by. Remove your bones and you’d be one sloppy mess!
Admittedly, you need less rigid internal and/or external support if you’re environment is a liquid. An octopus or squid or jellyfish is pretty helpless out of water. A liquid medium also allows you to grow to bigger sizes than would otherwise be the case. Whales do very nicely supported in water, but if beached, find themselves in some quite considerable life-threatening strife.
Finally, there’s a trade-off between locomotion and your support structure. You can’t really have an entirely near-rigid support structure since that would tend to hinder locomotion. Trees don’t walk around! Triffids are great sci-fi fare, but it’s hard to see that concept work in the real world. A ‘tree’ might have appendages that could manipulate objects in their environment, but their ‘legs’ would have to be really something else in order to move the ‘tree’ from A to B.
As to overall size, that in part is going to be a function of the gravity field you’re in. Presumably there’s a minimum size you have to be in order to have enough complexity to come to terms with being an intelligent species. There’s also a maximum size. Life forms are subject to the same sorts of engineering limiting factors as bridges and buildings. If you double your area (say your leg cross section), you triple your volume (your mass), so sooner or later something has to give as more and more mass needs to be supported by relatively less and less area. You can only grow so much in whatever gravity field limits that growth based on the materials you’re composed and constructed out of. Still, that’s going to cover a very wide range of possible sizes.
Sex: It’s hard to envision any complex life form undergoing asexual reproduction, say via splitting in half – down the middle – like relatively ‘simple’ cells do. There could be self-fertilization, but that limits genetic diversity so needed for relative rapid evolution. One assumes other life forms on other planets have a biological evolutionary process in place given how near essential diversity assists in overall survival.
Other bits and pieces can vary. External colouration is variable; smooth skin, scales, feathers, and fur/hair – no matter. Horns, tails, tusks or other adornments can be as many and varied as you’d like.
Essentials check-list:
*Eyes topside, minimum two.
*Ears somewhere; topside is better but not of necessity where ours are; two is better for determining direction, but three or more just creates confusion.
*Locomotion appendages, minimum one; more is better.
*Manipulative appendages, minimum one; more is better.
*A CPU brain – somewhere within.
*Size: Not too large; not too small.
*Genders: At least two to achieve genetic diversity, but not too many least things get too complicated.
*Support structure(s): Both internal and external appear to work, so that might be a toss-up.
Juggling all those essentials, with open slather on the majority of traits that are of little near mandatory consequence, well just say you could come up with a massive variety of life forms, from humanoid to quite unlike anything humanoid. Alien beings that are alien solely due to having pointed ears, facial dots, or wrinkled noses, while in the realm of plausibility, show a rather lack of imagination on the part of Hollywood bigwig writers, produces and directors.
So, here’s just one logically possible outward description of an advanced extraterrestrial intelligent life force with technology. In basic outline, I imagine a centaur-like structure, a being with four locomotion stubby tentacles ending in splayed out thick pads for ‘feet’.
There are also four relatively long manipulative tentacles emanating from roughly chest height. Two of the tentacle’s tips manipulate objects in much the same way as one hand’s finder and opposable thumb manipulate objects. The four tentacles in total equal the manipulative abilities of our two hands. There are four eyes on elevated stalks at the top of the ‘head’ giving a 360 degree field of view. Any two adjacent eyes give a stereoscopic view – depth perception – covering 180 degrees, though it can see farther into the infra-red relative to ourselves because it’s parent star is cooler and radiates more energy in the infra-red than the visible part of the electromagnetic (EM) spectrum. The body has a protective carapace and our being can withdraw its ‘leg’ and ‘arm’ tentacles inside if necessary like a turtle; ditto the soft ‘head’ structure, which has – you guessed it, four ears. Over all, the ‘skin’ is akin to thick tough leather. The being’s CPU ‘brain’ is located deep within the central body, not in the ‘head’, and so is well protected. Breathing is pretty much the same as ours – it has lungs. Ditto the digestive system. Like ourselves, it’s a carbon based life form and requires the same sorts of water intake as we require. The alien is native to a slightly lower gravity world than ours; its land based, and has a size roughly that of a large terrestrial dog or small sheep. There’s no tail.
Apart from my quickie off-the-top-of-my-head imaginary creation, well, you also gotta give some, and I stress some, Hollywood and sci-fi writers’ full credit for at least trying to think a bit outside of the box. The central question remains the biochemistry one, not the appearance one. Terrestrial life forms are so diversified in appearance that it’s difficult to imagine any pattern, any symmetry (or lack of same) that hasn't already been experimented with. However, physical appearance diversification is yet united in that diverse terrestrial life forms have collectively just a single overall biochemistry. Microbe or man; virus or vampire; plant or platypus; we’re all at the biochemical level near clones. So, we've had the diversification in outward appearance; might there equally be a diversification in what makes life, well, life?
But first, life has to have some abilities, and life has to exist within an environment that’s fit for, well, life. Both abilities and environments go way beyond life-as-we-know-it, if by that we restrict life-as-we-know-it to the very everyday familiar life forms that we perceive around us – even then, surprises abound.
Abilities: When it comes to special abilities relative to ourselves, well fish gotta swim (but so do dolphins, a Paramecium, squid, penguins, some turtles; even we humans make a rather feeble go at swimming but we’re not in the same league, far less the same ballpark as fish, etc.). And birds gotta fly (but so do bats and many insects; humans are natural flyers too – as long as it’s straight down). Clearly lots of organisms can move faster than we can. Many organisms have had abilities that have enabled them to survive for multi-millions of years; billions if you include micro-organisms. We've got a long way to go before we start making it in that ‘Guinness Book of Records’. Your dog can hear higher frequencies than you; your cat has a better sense of smell; many birds have sharper vision and many organisms can ‘see’ parts of the electromagnetic spectrum that we can’t.
But, not to worry, at least we tend to come top of the pops in the I.Q. category! Now the natural question is, what sort of evolved abilities or capabilities might intelligent aliens have that haven’t been thought of in anyone’s philosophy, apart from perhaps being mental giants and putting us to shame in that I.Q. category?
Environment: When we think of the typical environment that life finds itself in, we tend to think of our own traditional environment, one that has a fairly narrow temperature range; predictable alternating daylight and darkness intervals; one relatively free of harmful radiation; a fairly narrow pressure range; also a very narrow range of an environment that’s not too acidic, not to alkaline; a near constant atmospheric composition, etc. We don’t often tend to think that life in general, terrestrial life in particular can survive, even thrive outside what’s comfortable to us. How wrong we are if we think that! Relatively few complex organisms exist in extreme environments, though examples would fill many an essay all by itself. We all know about animals that can live in Earth’s Polar Regions and in her ultra dry and hot deserts. We know that fish survive at the high pressure, eternally dark abyssal depths, and that some fish can bury into mud and cocoon themselves from drought for extended periods. Still, that’s peanuts compared to what some micro-organisms can achieve. Without doing an exhaustive survey, you’ll find microbes surviving and thriving: high up in the atmosphere; kilometres beneath the surface of the earth; inside your digestive system; inside rocks; in battery acid equivalent environments; in extremely high saline environments; in extreme alkaline environments; in total darkness; in pressures that would crush you like an eggshell; in boiling water; in the near absence of water; in temperatures way below freezing; in toxic sludge; inside nuclear reactors; in environments totally free of oxygen. Some microbes can survive (but not thrive in) exposure to near absolute zero temperatures and the vacuum of outer space. The upshot is that the range of non-terrestrial planetary environments where we might detect, at least relatively simple life, has expanded to just about anywhere and everywhere.
Chemistry: Life-Not-As-We-Know-It: Humanoid, or non-humanoid life forms, with biochemistry very different from ours, is a reasonable rarity in science fiction. When such beings are depicted, they tend to be pure energy entities (fairly easily done via special effects), or something resembling terrestrial life forms albeit given an exotic biochemistry. Star Trek’s Horta are a case in point.
It’s going to be chemistry, not physiology that ultimately dictates life-not-as-we-know-it. Substitute liquid ammonia or ethane for water; silicon for carbon; copper for iron in the blood (Mr. Spock, anyone?), the literature of speculative astrobiology, not to mention the literature of science fiction as well as sci-fi TV series and films are relatively rare of really alien aliens, everything from pure energy beings to solid rock and crystalline life forms, but hardly non-existent. Alas, life-not-as-we-know-it, that is non-CHON (Carbon, Hydrogen, Oxygen & Nitrogen) life has been at best a ‘what if’ scientific and literary speculation of the purest kind. When subjected by biochemical specialists to critical examination, non-CHON biochemistries were found wanting as likely viable alternatives. For example, replacing carbon with silicon would have oxygen breathing aliens exhale not carbon dioxide but silicon dioxide – sand! Translated, we find the devil’s in the biochemical details as it were. While the possibility for alternative biochemistries can not be totally dismissed, we know CHON life can exist, so taking that certainty, we run with that first and foremost, when, in the first instance, looking for ET.
Really Far Out, Star Scout: Dark Life Composed of Dark Matter and Fuelled by Dark Energy: However, while on the subject of life-not-as-we-know-it, you’re in for a bit of a surprise.
You are a minority, and it has nothing to do with your sex, age, blood type, religion, racial or ethnic characteristics, I.Q., or any other similar or related thing.
You are a minority, even a rarity, in that all the stuffs (matter and energy) that make you, you, and make you tick, is in itself a minority or a rarity in the cosmos, and it’s not because most of the cosmos is ‘empty’ space (not that in quantum theory space can ever be 100% empty). All that you experience (see, hear, feel, smell and taste) around you, be it from your immediate surrounds out to the farthest reaches of the cosmos is the result of just 4% (or thereabouts) of the ‘stuff’ we know and love – electrons and positrons, protons (composed in turn of quarks) and anti-protons, neutrons (again in turn composed of quarks) and anti-neutrons, neutrinos and anti-neutrinos, photons (electromagnetism), the theoretical to date undetected gravitons (gravity), gluons (the strong nuclear force), etc. And 4% of anything represents a minority, even approaches the definition of rarity.
The other 96% (or thereabouts) of the cosmos is made up apparently of both ‘dark matter’ and ‘dark energy’, which isn't your run of the mill electrons, protons, neutrons, electromagnetism, gravity (although ‘dark matter’ exhibits a positive gravity akin to normal matter.), etc. yet can and does interact with the cosmos and its contents. It’s sort of like having a room full of 100 people, only 96 of them are ghosts, albeit physical enough to interact with the contents of the room (just like real ghosts allegedly do).
One needs to point out that thus far at least, there’s no actual known connection between ‘dark matter’ and ‘dark energy’ apart from the fact that neither is visible to us in the way that a star or light bulb is visible; thus, the common term ‘dark’. Both ‘dark matter’ and ‘dark energy’ have been detected by more indirect means, primarily their influences on the 4% of stuffs we can see.
The subject of astrobiology (as outlined above) deals mainly with the question of finding extraterrestrial life-as-we-know-it. That is, finding life like us based around traditional forms of matter and energy; life with similar chemistry, energy needs, and environmental requirements. However, astrobiologists do like to speculate and cast their minds far and wide and envision possible forms of life that fall in the category of life-not-as-we-know-it; life that makes use of exotic chemistries, unfamiliar energies, and (to us) extremely hostile environments.
So, the question proposed is could a form of ‘dark life’ originate and evolve out of some combination of ‘dark matter’ and/or ‘dark energy’? (This would be an ultimate life-not-as-we-know-it prize for astrobiologists.) Well, since we don’t really know what ‘dark matter’ is – its chemistry and other properties – and since we don’t have a handle on the nature of ‘dark energy’ either, one can’t conclude one way or another at this stage. Let’s just call it a whopping big “maybe”. Perhaps (the late) Sir Fred Hoyle’s Black Cloud concept as expressed in his sci-fi novel of that name, might not have been that far off the mark after all!
The major fly in this ointment is, I suspect, that ‘dark energy’ is a repulsive force, which at first glance, seems incompatible with life of any kind. Thus, for the moment, I’ll include it as a ‘dead end’. However, it’s early speculative days yet and there’s a long way to go before ruling anything either in, or out.
An idle thought however, we wonder what the missing 96% of the Universe is – just calling it ‘dark matter’ and ‘dark energy’ doesn't tell us what it is. Perhaps a ‘dark energy/matter’ being wonders what the missing 4% of their Universe is composed of!
Further recommended readings:
Barlowe, Wayne Douglas & Summers, Ian; Barlowe’s Guide to Extra-Terrestrials; Methuen of Australia, Sydney; 1980:
Cockell, Charles S.; Impossible Extinction: Natural Catastrophes and the Supremacy of the Microbial World; Cambridge University Press; Cambridge; 2003:
Friend, Tim; The Third Kingdom: The Untold Story of Archaea and the Future of Biotechnology; Joseph Henry Press, Washington, D.C.; 2007:
Gates, Evalyn; Einstein’s Telescope: The Hunt for Dark Matter and Dark Energy in the Universe; W.W. Norton & Co., New York; 2009:
Hooper, Dan; Dark Cosmos: In Search of Our Universe’s Missing Mass and Energy; Smithsonian Books, New York; 2006:
Huyghe, Patrick; The Field Guide to Extraterrestrials; New English Library, London; 1997:
Krauss, Lawrence M.; Quintessence: The Mystery of Missing Mass in the Universe; Vintage, London; 2001:
Naha, Ed; Science Fiction Aliens: A Starlog Photo Guidebook; Starlog Magazine, New York; 1977:
Siegel, Richard & Suares, Jean-Claude; Alien Creatures; Harper & Row, Sydney and Melbourne; 1978:
Ward, Peter; Life As We Do Not Know It: The NASA Search for (and Synthesis of) Alien Life; Penguin Books, New York; 2005:
Wharton, David A.; Life at the Limits: Organisms in Extreme Environments; Cambridge University Press, Cambridge; 2002: