We are a biological species, a planet of microbial organisms that about a half-billion years ago evolved multicellar creatures that eventually achieved sufficient complexity to develop a technology based on physics. It is not just our individual brains that have done this, but our entire societies, over time, which have slowly and laboriously developed this capability. We now understand the natural universe, (as a species, not as individuals) sufficiently to build spaceships and radio telescopes, the bare minimum technology required for interstellar travel and communication.

On this page I and others have speculated on possible alternatives to the human path to interstellar intercourse. We have considered the possibilities that our civilization will eventually construct artificial intelligences (computers) capable of replacing our human culture with a machine civilization.

We have also mused about other possibilities. perhaps entire ecosystems will eventually develop the complexity and structures necessary to support cognition, and perhaps even consciousness. We have talked about sentient coral reefs and rain forests, Gaia-like worlds like Lem’s “Solara”. There may be other possibilities, highly complex systems we can’t even conceive of which generate sufficient moving parts and organization to act in a purposeful and self-aware fashion. Stars are highly organized structures of fusion-powered plasmas, perhaps they are capable of intelligently perceiving and purposefully interfering with their environments. Perhaps the Galaxy itself has evolved consciousness.

We don’t really know if any of these possibilities are probable, or even possible, but we can’t rule them out either. There may be other intelligences in the cosmos, but we might have trouble recognizing them as such. And even if they exist, we have no assurance they, no matter how advanced and sophisticated, might recognize humanity as anything more than just another microbial infection.

We know more about the factors in the Drake Equation than he did. We now know that the number of suitable stars and planets for intelligence is much greater than we once thought, and that the possibilities for biological life are far higher than we once believed. But we also know that there are many more bottlenecks and obstacles to extra-terrestrial intelligence than we once expected, and that even though the universe is probably friendly to life, it may be hostile to intelligence. The opinion of the SETI community is now drifting away from the paradigm of the little green man at the radio telescope console, or at the spaceship controls, and openly speculating about machine civilizations, self-replicating Bracewell Probes, Jupiter Brains and Matrioshka Minds and other alternatives to science fiction’s traditional bug-eyed monster or Hive Mind.

Human beings have a life span of only decades, human societies a permanence of at best several centuries. Our entire experience as a technological civilization only extends, from the Paleolithic to the Present, a few milennia. The Galaxy is very old, and the speed of light is very slow. Perhaps intelligence in the cosmos proceeds at a much more leisurely schedule. Perhaps we are embedded in a symphony of voices and we aren’t even aware of it because the music is so slow, or because the lingua franca masquerades as some common chemical or physical process.

Or perhaps we’re the only game in town. I find this last possibility the most distasteful, even the most
unacceptable, of all. And it may turn out to also be the most fundamentally unanswerable question of all. The universe has always been generous with its questions, but very stingy with its answers.