Indeed. There is the often implicit assumption that an extraterrestrial intelligent species will be much like us, not only in form but thought and motivation, a notion reinforced by portrayals of aliens in film and television that are essentially humans with bumpy prosthetics and skin markings. The reality is that intelligent alien live will have evolved under conditions and environmental pressures that are likely very different from our evolutionary path and will be so dramatially different we might not even recognize them as being intelligent and vice versa. Even our most fundamental methods of interaction, such as using relationships between positive integers, may not correspond to the methods they use to quantify their experience, and it is likely to the point of certainty that their language or analogue thereof will be far more different than just word substitution and a differing relationship of grammar.
The assumption of fire being a necessary technology in the evolutionary chain seems obvious because of how critical it is for us, but there are any of a vast number of other paths to extracting energy from the environment. An aquatic species might evolve the means to secrete enzymes which would act directly on minerals to extract and refine metals or produce complex substances. Or a species might eschew the need for metallic alloys entirely, instead favoring allotropes of carbon as their basic structural material and conductor (as we likely will in the foreseeable future). Or there could be any number of other paths within the constraints of physics and chemistry which would allow some kind of industrial civilization arise and travel beyond its world. There is absolutely no reason to believe that the paths we’ve followed is unique or even particularly optimal.
The other issue about the Fermi Paradox and need for a so-called “Great Filter” was noted by Shagnasty; space is so vast that there could be tens of thousands of technological society scattered throughout our galaxy alone and we may never detect a signal that was not deliberately directed at us. The greatest distance that the most powerful radio signals humanity has ever produced (somewhat ironically from ballistic missile early warning systems) could be observed only out to less than 200 light years even with very powerful antenna, and over longer distances even focused coherent signals will be absorbed by the interstellar medium, notwithstanding the duration it takes for them to travel and the intervening movement of stars within the galaxy. To have a hope of detecting and communicating with an alien species using conventional radio or optical means they’d have to be within a few tens of light years of Earth, and there are few enough stars in that region that fit the conditionswhich we currently believe support habitability (although, again, we shoudln’t allow our limited imagination restrict what totally alien life might be like or where it could develop; any location with excess radiant energy has the potential to support some kind of thermodynamically self-regulating and self-reproducing system that we could consider to be alive).
Even if we posit that life is a common occurrence within the local region around our solar system, we have to come to terms with the fact that the odds of it arising in parallel with our own is dramatically unlikely. Our planet has been around for about 4.5 Byr, and life likely formed a few hundred million years after, and yet it took until the last few million years for a tool making species to start to expand conquer regions beyond its native environment, only tens of thousands since we’ve developed the technologies to transform ourselves to be somewhat independent of the natural ebb and flow of the ecosystem, and only the last couple hundred until we could be said to have started to have a grasp on understanding and controlling even one of the fundamental forces of nature. In that time, numerous technological species could have risen and fallen or transformed into something beyond what we conceive as existance, and in the case of the latter they may regard us of having less intelligence than we do of ants. And frankly, any sophisticated species capable of communicating or travelling over interstellar distances won’t be using radio or light to communicate; they’d likely use coherent gravity waves which can travel cosmic distances unimpeded and without losing much fidelity, or something even more exotic, which we currently have no way to even detect much less decode. Such means of communication would require the command of enormous energy and detection methods so fine that they are not only beyond our technological grasp for the foreseeable future, we don’t even know how they could be workable, but the basic physics makes them plausible regardless.
If and when we meet an advanced alien species the interaction will probably be akin to that portrayed in 2001: A Space Odyssey, i.e. completely incomprehensible to us, and beyond our means to control or escape. Such a disparity in technology would likely not go well for us if they mean us harm or even if they are just indifferent to our own survival, and so if there is truly a “great filter” it is likely that the earlier species to advance technologically and explore the stars may reflexively squash others who may rise to compete with or threaten them. Or, due to a terrible miscalculation of scale the entire battle fleet may have been accidentally swallowed by a small dog. Some experts believe that this may be occurring all the time, and we are powerless to stop it.
“It’s just life,” they say.
(Apologies to the late Douglas Adams for shamelessly cribbing one of his best jokes.)
Stranger