On Extraterrestrial Evolution
2011 by Dale Bryant
Virtually all reports of contact with, or sightings of, alleged creatures of extraterrestrial origin, describe these beings as humanoid, i.e., possessing large heads with two eyes, a thorax or torso, with two pair of extremities or limbs, the lower pair functioning as legs, as these beings primary mode of locomotion happens to be bipedal. This is all very interesting; the form that a body takes is dictated by its geological surroundings - including and especially available food sources, atmospheric composition, air temperature and pressure, amount of received sunlight, natural enemies - even variations in the gravitational pull of the host planet itself according to geographic location. All of these factors are highly variable at any given locale and conspire to shape our bodies - even as finely as the cusps on our molar and pre-molar teeth, to accommodate the foods we will eat as we begin a solid food diet. This is why humans look the way they do and why gazelles, rabbits, fish and spiders look the way they do, not to mention all the different general body types involved (vertebrates, invertebrates, arthropods (those with articulated limbs or segmented bodies), etc.)
The possibility that intelligent extraterrestrial beings would be humanoid in form is barely even remotely possible. The evolutionary chain of events, through the process of natural selection, which includes physical and mental adaptation and inheritance of favorable characteristics, that led to H. sapiens, was a very specific one and occurred only once on this planet; its recurrence on some other world is unthinkable; any life forms on another planet would likely be something other than humanoid and not even remotely resemble any form of life on Earth.
The humanoid form is based on an anthropoid body plan, one of the many body plans of earthly fauna. The anthropoid cranium positions two eyes, anteriorly, or at the front of the skull. This arrangement provides binocular, or stereoscopic vision to the possessor, which is very sensitive to the movement of its prey, indicating a predatory carnivorous ancestry. Our earliest mammalian ancestors were herbivorous, with eyes positioned at the sides of the head, providing a more panoramic view much less sensitive to movement. The anthropoid body plan also includes four limbs in two pairs--the upper pair was used by our last common ancestor for swinging from branch to branch among the trees and even included hands for that form of locomotion known as brachiation. The bottom pair of limbs became important in our upright, erect posture for moving across large swaths of ground after we transitioned from an arboreal existence to the necessary mode of locomotion adapted for the savanna, bipedalism. To expect that beings from another world would have taken essentially the same evolutionary pathway as human beings is akin to expecting that they speak English too! Given any similarities, it would be even more likely that these alleged humanoid forms are actually us--from a very distant future and evolutionary development--come back to visit ourselves, via some unlikely, but plausible, manipulation of the fourth dimension--time.
The scientists who study the possibilities of life on other planets are called Astrobiologists and Exobiologists. What do you think an extraterrestrial intelligence, should they actually exist, might look like?