no wai!

What’s “axenism”? I admit I just made the word up, but etymologically speaking, axenism is to atheism what xenology is to theology. An axenist is an unbeliever with respect to extraterrestrial intelligence — one who thinks alien civilizations don’t exist, at least not anywhere in our galaxy.

So why do I think alien civilizations don’t exist? There are two key observations to make.

First, when we split the probability for extraterrestrial intelligence into several factors à la Drake (e.g., the probability for simple replicators to arise, and the probability for life to develop intelligence), pick some reasonable-sounding estimates, and multiply them together, the order-of-magnitude uncertainties add up to a very broad range of possible numbers of alien civilizations — anything from thousands per galaxy to less than one per region the size of our observable universe.

Second, the total lack of evidence for extraterrestrial intelligence suggests that among the all the many possible numbers of civilizations compatible with Drake-style calculations, very low numbers are the most likely to be right. As Fermi observed, if they were out there, they would have been here, and we would have noticed, or more likely failed to exist in the first place.

In short, not only is axenism compatible with all our knowledge, there is strong evidence in its favor.

Of course, various people disagree with various parts of this story.

  • It’s tempting to note that we humans form a technological civilization and conclude that, apparently, technological civilizations must not be that improbable. This gets into sticky issues of anthropic reasoning, on which philosophers disagree. Being a technological civilization is always what a typical technological civilization observes, no matter how rare technological civilizations are (it’s a problem if there aren’t any at all, but the universe is extremely big at least, and quite possibly infinite). Some infer from this that the information can be thrown out entirely. Others do think we should favor hypotheses that predict many technological civilizations. Even then, if the rest of my case holds, it’s a puzzle why we came into existence so late. Humanity’s time-of-birth seems to be a typical moment in a mostly empty universe where civilizations don’t interact until very late, if at all; it seems to be a highly atypical moment in a universe where many civilizations pop up as soon as conditions allow, then colonize their future light cone.
  • Some people might say the biological study of evolution and the origins of life tells us the probability of life eventually popping up on an Earthlike planet is quite high. If this is true, I would love to be enlightened. Creationist comparisons with tornados in junkyards are, of course, rubbish. But that’s still consistent with abiogenesis being extremely improbable. To the best of my knowledge, biologists are not able to confidently state any lower bound on the probability for abiogenesis, of the kind that shows it has to happen on at least, say, one in ten billion Earthlike planets.
  • It’s also sometimes claimed that, since highly intelligent behavior evolved in different species (primates, dolphins, etc), it must not be that improbable. Perhaps, but it could still be the case that the step from animal intelligence to full-blown human-level intelligence is very rare.
  • There is the argument that life arose on Earth early in the available window of opportunity, which is more likely if life is probable than if life is improbable. This argument is much less impressive if, as seems very possible, several hard steps were needed. In that case, we would expect them to be about evenly spaced. It also fails if Earth life originated on Mars, which is claimed to have been suitable for early life long before Earth was.
  • The claim that interstellar (even intergalactic) travel is infeasible is absurd. The problem of astronauts dying can be solved through relativistic dilation, generation ships, life extension, uploading, or sending artificial intelligence. The amount of resources required is huge relative to the present-day economy of Earth, but tiny relative to the economy of a solar-system-encompassing civilization, and tiny relative to the returns.
  • The claim that nobody would want to colonize the stars is absurd. It takes only one, as they say; self-replication will do the rest. Most or all advanced civilizations will prefer certain configurations of matter to others. Star systems have building materials, energy, perhaps information, potential humanitarian disasters, potential threats. In civilizations where groups and individuals vary in their expansionism, the expansionist ones will tend to dominate in the long run. The “Zoo Hypothesis” that aliens are keeping us in the dark on purpose requires very strange motivations.
  • Famous SETI researcher Jill Tarter responds to the question “then where are they” by saying something along the lines of “maybe they are here; maybe there are probes messing around in the asteroid belt and we can look for them”. This makes her a UFO believer, except at a slightly greater distance, and on no empirical evidence rather than flawed empirical evidence. Her suggestion explains nothing at all; the mystery is not literally why they’re not here; it’s why, in the hundreds of millions of years that they’ve had, they haven’t done anything, here or elsewhere, with visible or life-eradicating side effects.
  • Some have suggested all complex life in the galaxy is periodically toasted by gamma ray bursts or other disasters. That could be part of the explanation why we haven’t yet been visited, but among other problems, it doesn’t really explain why there’s no wave from any other galaxy.
  • Lastly, there are the nakedly religious objections that make no rational sense whatsoever. As Carl Sagan put it in Contact, if there were nobody else out there, wouldn’t that be an awful waste of space? Well, yes. And by that reasoning, Saturn is made out of strawberry and lemon ice cream, and its rings are delicious wafers. As Sagan knew perfectly well, Nature is indifferent to human concerns. Wasting stuff is just what it does. If the emptiness of the universe bothers us, we will have to send colonization waves and fill it with fun and beautiful things ourselves.

PS: Michael Anissimov and George Dvorsky have covered this topic before.