What Are Alien Species Like? Symmetrical, Solid, and Seeing (Probably)

By Amos Zeeberg (Discover Web Editor) | June 19, 2009 3:41 pm

Codex Futurius LogoWelcome to another juicy installment of the Codex Futurius project, this blog’s never-ending quest to explore the timeless scientific ideas raised by science fiction. This question about what kind of aliens we may eventually run into goes to Rocco Mancinelli of SETI. Thanks to Dr. Mancinelli for the enlightening contribution and to Jennifer Ouellette, the director the NAS’ Science and Entertainment Exchange (SEEx) program, for connecting us with him.

What is the most likely form an alien would take?
Life’s architecture is difficult to predict because it depends on many factors involving the interaction of the environment and life through evolution and natural selection. We can, however, make some generalizations based on the vast number of morphological forms that life takes on earth.

Life on earth ranges from microscopic spheres and rods to macroscopic creatures exhibiting wide variations in their morphologies (e.g., spiders to humans). Nevertheless, nearly all life (everything except sponges) exhibits symmetry—either bilateral or radial symmetry. In bilateral symmetry (also called plane symmetry), only one plane, called the sagittal plane, will divide an organism into roughly mirror image halves. An organism with radial symmetry has no left or right sides, only a top and a bottom (dorsal and ventral surface). An alien life form, therefore, would most likely be symmetrical. The type of symmetry would be influenced on the environment in which it lived. From our basic knowledge of survival of macroscopic organisms whether they be aquatic or terrestrial it seems that bilateral symmetry dominates.

The possession of other specific attributes (e.g., ability to hear, see, smell, move, etc.) depends on the environment and competition for resources for survival. For example, when we think of “seeing,” we think of “eyes” first. But if we think of the function (sensing specific wavelengths of light) rather than the specific physical attribute, it opens a plethora of ways in which we can imagine “seeing,” ranging from the photosensors for phototaxis in bacteria to the compound eyes of some insects. The uses to which life puts its sensory perception mechanism of light ranges from finding food to escaping from predators. It would seem logical that an alien would have some type of light sensory perception mechanism if it lived on the surface of a planet. What the physical make-up and appearance of that light sensory perception mechanism would be is difficult to define. The perception of light is not just limited to the type of perception just described, that is, “seeing”, but also to perception by photopigments (e.g., chlorophylls) used for capturing light energy to produce cellular energy for use by the organism (i.e., photosynthesis).

Following this line of logic, the form that an alien would take is the form that makes it survive and reproduce best in its environment. If I had to make a guess it would be that it would have symmetry (probably bilateral symmetry), capable of light perception, and probably motile (increases chances of finding nutrients and escaping predators). To say anything more specific would require knowing the planetary environment in which it lived.

What about the form of an intelligent alien, specifically? Would it even need to have a solid form?
First, what is intelligence? As defined by H. J. Jerison, intelligence is the behavioral consequence of the total neural-information processing capacity in representative adults of a species, adjusted for the capacity to control routine bodily functions. This can be related to encephalization. Encephalization is defined as the amount of brain mass exceeding that related to an animal’s total body mass. Quantifying encephalization has been argued to be directly related to that animal’s level of intelligence. Brain-to-body mass ratio (also known as the encephalization quotient, or EQ) is a rough estimate of the possible intelligence of an organism, and is defined as the ratio of the actual brain mass to the expected brain mass of a typical organism that size. On average, the larger an organism is, the more brain mass is required for basic survival tasks, such as breathing and thermoregulation. Therefore, the larger the brain relative to the body, the more brain mass should be available for more complex cognitive tasks. It has been shown that dolphins, which have the highest brain-to-body mass ratio of all cetaceans, are able to communicate with each other and are thought to be intelligent to some degree. Humans have a higher brain-to-body mass ratio than dolphins.

To this day there is no broadly definition of “life”. The Darwinian, or genetic, definition of life is the most accepted today. It holds that life is self-sustained chemical system capable of undergoing evolution by natural selection. Applying this definition to life suggests that it would be a solid form.

CATEGORIZED UNDER: Aliens, Codex Futurius

Comments (5)

Links to this Post

  1. Conspirama | June 19, 2009
  1. I think this is one place where science fiction has let us down. While there are a handful of truly imaginative works regarding what extraterrestrial life might be like, the fact is that the general template shown in popular works is essentially the same as ours.

    Much of this comes from practical decisions, of course. It’s easier to put a costume on an actor than it is to create something truly novel with which the audience might not be able to identify.

  2. heteromeles

    Actually, Dr. Mancinelli said something interesting, because it shows his perceptual biases.

    Are most organisms symmetrical? Most organisms are bacterial, and I think a lot of them are symmetrical, except for, of course, spirochaetes. Since he is a human studying extremophile bacteria, this declaration makes sense.

    However, most eukaryotes are not symmetrical at all, because most eukaryotes are things like plants, fungi, algae and other protists that are definitely not symmetrical. One only has to think about the beautiful symmetries of flowers. Eye-catching, right? Why are they eye-catching? Because their symmetry stands out in the chaotic mass of fractal plants that covers so much of the landscape.

    Do I expect alien intelligent life to be assymetrical? Not particularly. However, that’s because this primitive human can only define intelligence by how it interacts with me, and that requires things like moving symbolic communication. As a counter-example, plants have some amazingly complex interactions with their local environment–symbioses with fungi, bacteria, pollinators, chemical communications with other plants, competition with plants, anti-predator devices, and so forth–yet even if there is a controlling intelligence behind all this, I can’t communicate with it, and therefore, by default, I treat it as unintelligent.

    Problem here is, intelligence can only be determined through interaction, and a truly alien intelligence would probably not even be recognizable by us, even if we lived together.

    Dr. Mancinelli made a good contribution here, but inadvertently, he also showed how our biases shape what we’re looking for. It’s an important lesson.

  3. Amos Zeeberg (Discover Web Editor)

    Interesting point, hetermeles, but aren’t most fungi and plants radially symmetrical about their major axes? The symmetry isn’t perfect on the level of branches, obviously [I think leaf-bearing structures tend to go in a spiraling rather than symmetrical pattern], but the basic structure is radially symmetric. And the leaves of most plants are bilaterally symmetric — again, not in every detail but in essential structure].

  4. Ryan Upton

    The question is wrong.

    When trying to find a solution to hard questions the best way is to start by closely look at the question. The question really implies other questions that need to be addressed first in order to answer “What do aliens look like?”. The implied questions are firstly, “what is life?” and the secondly, “what environment is that life living in?”

    Assuming you mean intelligent life like human beings we would have to realise that we are a product of our environment. In our environment we perform a number of tasks. We reproduce, we efficiently find and distribute energy, we fight entropy, we evolve. Really if you boil it down to the core element we are a really long number. Almost a real number. This number is finely tuned to our environment. The more we evolve the longer and more tuned that number becomes. Each of us is a weighted constantly changing very precise number.

    Lower life forms may also have a number that represents them. The number does not have to be as precise for lower life forms. The number representing a single ant would not need to be as long or complex as the number representing a human being.

    The number is closely matched to the environment. In fact the tuned number forms part of a feedback loop. A person in a coma for 10 years will have a simpler number than a person active in the community. Consequently if we want to understand what an alien looks like we must understand the environment they come from.

    I could point here to the Drake equation. The drake equation does not have enough variables and needs extra inputs. The implied question is would life occur under different environments than ours? The answer is most likely no. There are a number of very unique circumstances that conspired to produce us.

    The key is chemistry. Water is a very good solvent. Hydrocarbons cannot dissolve materials as well and this impedes development of complex life. Also carbon has four places to form bonds allowing complex chains necessary for carbon based life. Silicon also has four bonds and is not as easy to use with water. Extremophiles can survive outside the basic chemistry and environment but are restricted in the optimal growth necessary for intelligent life.

    Additionally earths liquid metal core maintained by the low orbit of the moon is a fairly unique planetary event. The liquid core creates a magnetic field protecting us from the suns radiation. The tectonic plate action helps to cool the outer layer enough to support life preventing Venus like greenhouse effects. Additionally black smokers, underwater volcanoes allow life to get started. Tides and seasons allow a repeatable cycle helping evolution.

    We also have very circular orbits creating stable environments in order for life to develop. We have Jupiter as a big protector from collisions giving life an average window of 700 million years to develop between impacts. The earth is large enough to produce life without risking mars like atmosphere evaporation or Venus greenhouse. The land mass is large enough for creatures to evolve out of the oceans and develop tools and fire. All of these conditions would have to be replicated in order to produce intelligent life.

    Certain characteristics are necessary and have evolved several times taking the same form. Eyes for example have evolved several times and always look the same. It would be safe to assume hearing, taste and smell share this characteristic. Theses sensors are usually located close to the brain and usually some place high. Hands with opposable thumbs would be evident if the aliens evolve from trees which they most likely do.

    Assume all these factors could be replicated the question becomes what factors could be different and still have intelligent life. The asteroid that destroyed the dinosaurs could be different. Comparing the Ichthyosaurus and Dolphins is a good example. Both creatures look and perform the same. One is a dinosaur and the other is a mammal. Assuming the underlying architectures roughly parallel our evolution our fellow aliens may be more dinosaur like if they missed an asteroid.

    If they have had a few extra asteroids they maybe different again.
    If the aliens are more evolved they may be more silicon machines than biological.
    The surprise would be how similar to us they really are and probably could even be mistaken for human.

    The real difference would be language and culture.

    If you want to understand the form of an alien species you have to examine its environment.


Discover's Newsletter

Sign up to get the latest science news delivered weekly right to your inbox!


See More

Collapse bottom bar

Login to your Account

E-mail address:
Remember me
Forgot your password?
No problem. Click here to have it e-mailed to you.

Not Registered Yet?

Register now for FREE. Registration only takes a few minutes to complete. Register now »