I have been a supporter of the Search for Extraterrestrial Intelligence (SETI) since I learned of its existence. Essentially, SETI is a search for technosignatures of alien origin, specifically using radio astronomy. However, I occasionally encounter skepticism toward SETI, and I love to engage with fellow skeptics on topic about which we disagree. I recently received an e-mail with a fairly typical skeptical perspective:
“I am sure we will eventually find signs or evidence of life outside our solar system but the likelihood of finding a life form that can communicate on a level that we can understand seems so unlikely as to be not worth pursuing from an economic point of view.”
His basic argument is that, in order for us to communicate with an alien technological species they would have to be very similar to us. This would require a degree of “parallel evolution” that is fantastically unlikely. Even given the vastness of the universe, he feels the probably is simply too close to zero to justify any investment. I disagree, however, with his core premise.
First let me say that we simply have no idea how common life, intelligent life, and technological civilizations are in the universe. That is one of the questions SETI is attempting to answer. We suffer from the so-called “N of 1” problem – we have only one example of life and a technological species. He agrees life is likely common, which I think is likely, but feels technological species are exceedingly rare, but we simply have no basis for this conclusion. The evolution of greater intelligence occurred in many clades on Earth. Many, of course, like insects, will never achieve technological status, but that doesn’t matter. Greater intelligence is a massive evolutionary advantage, and is likely to occur in many lines.
There is a threshold that needs to be crossed – cultural evolution, cumulative species knowledge, the ability to manipulate the environment, perhaps something like language. We see elements of these in many species. Again, there is an N of 1 problem, but we can say that it is probable that many or even most planets with life will eventually produce an intelligent and possibly technological species. Even if the percentage is small, like 1%, that still results in a universe silly with intelligence. The e-mailer is assuming that the percentage is more like one in a trillion.
It also seems that a core part of this assumption of extreme rarity is the claim that any intelligent species we can communicate with needs to be evolutionarily very similar to us, but I think this is false. In reality, once again, we just don’t really know. But there has been a lot of speculation about this – are there commonalities that even alien intelligent species might share, like math? The laws of physics would be the same for any such species, and this would provide a common ground on which we can build communication and eventual understanding.
What we don’t know is how unique and quirky human intelligence is, because we have nothing to compare it too. That is part of the fascination with encountering a truly alien intelligence – can there be solutions to the problem of evolving a dominant intelligence that are so divergent as to be mutually incomprehensible? Is the movie Arrival likely to be closer to the truth, or the many humanoid species of Star Trek?
Further, I should point out, that the success of SETI does not require that we understand any signals we intercept. Just knowing they are there is groundbreaking information. But SETI proponents also argue that – if we do intercept a directed signal, that means the alien species was trying to communicate, which means they are trying to be understood and likely would be trying to leverage universal concepts, like math, to help us understand them.
What all this could mean is – that an alien species, the product of a completely different evolutionary history, that may look nothing like us, with differences that we cannot even imagine, may still be able to communicate with us. We will likely speak the common languages of math and science – almost by definition, if they are trying to communicate with us through radio signals.
So I think a better way to frame the probabilities of SETI seeing some kind of success as – well, we don’t really know, which is kind of the point. But it is possible that, on average, the nearest technological civilization is incredibly far away, not in our galaxy. There is also the variable of time – we don’t know how long such civilizations survive, on average. Even if it’s a million years, that is a brief slice of time on a universal scale. Civilizations may be temporally rare, if not spacially rare. So is it worth it?
I still think the answer is yes. First, SETI institutionally does a lot of radio astronomy not related to searching for alien signals. So as a matter of investment and efficiency, they are doing it right, and even if the SETI component never produces a positive result, they are still doing a lot of good radio astronomy. Further, a negative result is still a result. It’s data. It tells us something important about our universe. Learning that life on Earth is even more rare, more precious, than we imagined can be powerful.
Even if the chance of a positive outcome is extremely low, the benefits would be massive. It is reasonable, in my opinion, for our scientific investments to be spread out in terms of ROI (like any smart investment portfolio). Sure, we put much of our research money into high probability endeavors. But we can also invest in progressively uncertain outcomes, proportional to their probability and payoff. We also know that some basic science is just following curiosity, with no calculation of ROI, and that this approach tends to pay off on a regular basis and often in unexpected ways.
As an aside, this is different than proposals that break the laws of physics, or have massive fatal flaws, or have already been adequately shown to be false but proponents won’t give up. I don’t think we need to keep researching homeopathy or free energy. But these are fundamentally different than SETI.
I therefore hope to see SETI continue and thrive. It is doing good science and providing useful observations, even if we don’t hit pay dirt. But of course, I hope to live to see the day when we do find a signal. What would be more fascinating than that?
