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

Welcome 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.