But while pushing alien-ness to its limits is an important exercise for stretching our imaginations, I am increasingly compelled by the anthropocentric-sounding idea that ETs might actually tend to look just like we do. Terrestrial examples of convergent evolution show just how powerful niches are at producing uncannily similar forms from widely different origins. A classic example is the thylacine, an Australian marsupial thought to have gone extinct in the 1930s but occasionally still reported and thus possibly still surviving as a small relict population in the Outback. Although its most recent common ancestor with canines would be some shrew-like creature way back in the Jurassic period (145-200 million years ago)-much older than its common ancestor with the kangaroo, in other words-it looks uncannily like a wolf, and old films of the animal show that it moves like a wolf and has similar mannerisms. This is because in an island continent with no canines, it evolved to fill the exact same niche, "apex predator," that large canines did elsewhere. (Richard Dawkins reports that thylacine skulls were actually used to trick students in Oxford zoology exams.)
An advanced spacefaring species will have (at least at some point) occupied the same niche on its planet that we do now on ours-what you might call "apex animal": a highly social, tool- and machine-using species having gained mastery over the planet's raw materials and other species through its intellect, physical dexterity, and complex social organization and culture. These capabilities in and of themselves don't necessarily predict having a humanoid body plan-one could imagine a super-smart, social, tool-using amoeba or octopus or a big-brained cockroach. But to arrive at those capacities, that species would need to have undergone certain pressures and constraints over its long evolutionary past that would narrow the realistic range of forms it could actually end up taking.
THE ANTHROPIC PATH
Principally, such a species would need to have come up via an early threshold of tool manufacture and use coupled with complex social manipulation. That means, I suspect, being land-dwelling (rules out soft body forms like octopi), being of a certain size to support a large brain (rules out amoebae), and having an endoskeleton (rather than exoskeleton) that can support that body size on land (rules out cockroaches).
More to the point, such a species would have to have manipulating appendages-minimally two, so they can coordinate and work in opposition-"but" (and this is important) those appendages would have necessarily evolved from structures serving some "other" purpose like locomotion, through a process of "exaptation" (existing traits assuming new functions). Major organs and limbs with specialized duties don't just spring into being fully formed. Thus, the original body plan would have had at least double this number of locomotor appendages so that, through said exaptation and related changes, it could concentrate locomotor duties on the remaining ones. For land animals over a certain size, more than four legs is redundant and impractical, so more than likely, the ancestors of our hypothetical species would have been quadrupedal, while it itself would be a biped with arms terminating in something like hands.
Our big social and tool-using brain coevolved with our dextrous hand and opposable thumb. The two are inseparable in our evolution, in fact, and not simply because of tool use. Manipulation of the social world was just as key to our development of higher intelligence as manipulation of the physical world, and we know they occurred together. The parts of the brain that handle language remain closely connected to those that control manual manipulation and dexterity, and in fact language is now thought to have evolved from gesture, not from primitive vocalizations.
It's an interesting story how the shifting duties of our feet and hands changed our head (and vice versa): As bipedalism freed the hands for tool use, tool use (specifically, knives and fire) freed the jaw from its biting duties and relieved much of its chewing duties. This both flattened the face and enabled the oral cavity and breathing apparatus to become more elaborate so the production of vocal language could take over and expand the former job of gesture-creating the beginnings of symbolism and freeing the hands now to concentrate fully on manipulation of the physical world. All the while, of course, the cortex was ballooning to manage these new capacities as well as drive them. Notably, the transition from gesture to vocal language enabled communication to be "silent" and thus gave rise to a whole inner world of self-talk, a watershed development in the history of self-consciousness.
Bipedalism is significant in this story not only because it freed the hands for other things but also because it imposed a restriction on the diameter of the birth canal. This restriction on a massive-brained creature forced "premature" birth and thus prolonged postnatal vulnerability, necessitating lengthy maternal care and socialization and thus enculturation-the emergence of an extrasomatic memory, the beginning of culture and memes as a parallel form of inheritance to genes.
All this is to say there was a parsimonious relationship between intelligence and manipulation of the social and material world, and they occurred of a piece. The structure of the forelimbs, the shape of the face, the shape of the head, the shape of the pelvis, and the upright stance all evolved together as part of a single trajectory within an emerging milieu of symbolic cultural knowledge and memory (the emerging no"osphere), each of these traits feeding back on the others, creating a "perfect storm" of pressure to become humanoid.
Any form in nature or art reflects a kind of compromise among various current pressures and those that shaped it in its past; indeed, the main current pressure on an organism is the inertia of its own history. Having, say, an extra couple of hands or, heck, wings might seem useful, but there's no structural precedent for it. Imagining the bizarre forms ETs could take is a fun exercise, but all too often it leaves out the boring story of where the being had to have come from. I don't think it simply reflects a failure of imagination (or reactionary anthropocentrism) to suggest that our erect, bipedal plan couldn't be a more realistic, simple solution from the standpoint both of our future potential and our past history-where we are going and where we came from. In the future, we may be able to jettison most of the physical body that got us to this point, but that body is still like the enormous first stage of an Apollo rocket-it was completely necessary to get us into the "space" of higher intelligence, and I really wonder whether it could have happened any other way. I suspect all these same factors will have driven the rise of intelligent beings elsewhere; and even if such beings transcend to become "posthuman" machines, that humanoid past will nevertheless leave some kind of imprint on their psyches, culture, or spirit.
ARE ETS OUR CONFLUENT KIN?
The 20th-century Hermetic philosopher Rene Schwaller de Lubicz argued that all biological forms contain and prefigure the human body and soul. As retrograde and ignorantly teleological as that idea may seem in our postmodern, ecological, anti-anthropocentrist age, I think Schwaller's idea is worth at least pausing to consider, if only as a thought experiment. What if the forces giving rise to higher intelligence are so similar in biospheres throughout the universe that not only the humanoid body plan but even the "human spirit" are Cosmic universals? I suspect that, just as intelligent extraterrestrials will frequently (if not always) pass through a humanoid phase at the culmination of their biological evolution, they will also reflect (at least in that phase) the same motives, conflicts, ambitions, insecurities, desires, fears, hopes, etc. that we do, because their history, like their evolution, will reflect the same opposing forces and pressures. Again, this will undoubtedly leave an imprint, of some kind, on their posthuman trajectory.
We could even take this speculation one step further. Some astrobiologists speak of a Galactic Club of sufficiently advanced technological civilizations who share their knowledge with each other. What if our destiny is really, literally, to join a Galactic "Family"? What if the ages-old intuition that our visitors' involvement with us has to do with breeding or hybridization reflects a kind of four-dimensional model of Cosmic kinship, in which all intelligences throughout the Cosmos converge, not merely on a body plan but even on a shared genetic code?
Maybe there is something to the Hermetic intuition that "Anthropos", some fully human being, stands at the end of Cosmic history, as its completion and pinnacle. I've always disliked the warm and fuzzy vision of universal brother- and sisterhood espoused by some UFO believers and expressed (for example) at the end of "Close Encounters". But what if we actually share with ETs not a common ancestor in the past but a common descendent in the future, a Star Child? Perhaps "confluent" kinship should be the central organizing concept for reckoning Cosmic relatedness in a future exoanthropology"
Reference: mysteries-and-strangeness.blogspot.com
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