36 civilizations in the galaxy?

A new analysis is getting some attention, one claiming to have refined the old Drake equation and produced firmer numbers, leading to this conclusion:

Under the strictest set of assumptions – where, as on Earth, life forms between 4.5bn and 5.5bn years after star formation – there are likely between four and 211 civilisations in the Milky Way today capable of communicating with others, with 36 the most likely figure.

Whenever I see these types of analyses, I’m always interested in two questions.  What new data is available?  And what remaining assumptions are being made?  The new data is likely all the exoplanet information that has come out in recent years, which makes sense.  But the assumptions include a major one:

“Basically, we made the assumption that intelligent life would form on other [Earth-like] planets like it has on Earth, so within a few billion years life would automatically form as a natural part of evolution,” said Conselice.

The assumption, known as the Astrobiological Copernican Principle, is fair as everything from chemical reactions to star formation is known to occur if the conditions are right, he said. “[If intelligent life forms] in a scientific way, not just a random way or just a very unique way, then you would expect at least this many civilisations within our galaxy,” he said.

It might be reasonable to assume that given the right conditions, life will arise.  It started early enough on Earth to make that a defensible assumption.  We might even get away with assuming photosynthesis (for a biosphere exposed to a sun) is inevitable.

But the further we go along the evolutionary timeline, the more contingent the developments get.  How inevitable was the development of eukaryotic life, which may have been based on a single chance event?  Or of sexual reproduction?  It’s worth noting that Earth was 86% of its current age before complex life evolved, an event that required all the above plus high oxygen levels, which itself was dependent on numerous prior events in Earth’s history, both biological and geological.

And a civilization producing species requires more than just intelligence, but a body plan that allows manipulation of the environment, at various scales, including fine detailed workmanship.  In other words, the hand is as important as the brain, and its development was based on numerous contingencies in our evolutionary history.

Of course, there are likely alternate paths to the same capabilities.  But just blindly assuming that it’s inevitable is simply ignoring our own evolutionary history, which makes this analysis vacuous, just astrophysicists publishing their opinion on matters that are broader than the scope of their expertise.  As PZ Myers notes in his own scathing assessment, they really need to include a competent evolutionary biologist in their collaboration.

These assumptions also have to include one of a couple of starkly pessimistic ones.  First, that interstellar travel is impossible, even for uncrewed probes, or so monstrously costly that no one bothers.  If even one civilization in the 13 billion year history of the galaxy accomplished it, they should be everywhere within 100 million years.  Or second, that civilizations destroy themselves before they are able to spread.  That might be a true tendency, but assuming zero civilizations escape it is pretty dark.

If we modify their assumptions to take the probability of a civilization developing on a planet like ours down to 1%, which given all the chance events seems warranted, then we’re alone in the galaxy.  Dropping it lower  increases the distance to our nearest neighbors accordingly.  Throw in Fermi’s paradox (which looks less paradoxical when we’re realistic in our assumptions), and we get convergence that intelligent life is more rare than these folks want to admit.

Unless of course I’m missing something?

18 thoughts on “36 civilizations in the galaxy?

  1. [stepping out of the choir box]

    I think this statement is key:
    If even one civilization in the 13 billion year history of the galaxy accomplished [interstellar travel], they should be everywhere within 100 million years.

    I’m inclined to think that development of intelligent life is inevitable, but I think of the development in terms of half-lives. So what is the half-life of the development of single-celled life given earthtype conditions. (Seems fairly short, given that life started just about as soon as it could.). What is the half-life of going to multicellular, going to terrestrial, going to dexterous + intelligent, going to technological?

    Given that, like you say, what are the chances that two separate technological intelligences develop within that 100 million year window?


    Liked by 1 person

    1. Half lives is a good way to think of it. We also have to remember that the sun will heat things up in another billion or so years, so the window will close.

      Closely related to the 100 million year window question is, once a civilization manages to expand beyond a small region of the galaxy, how long can it last. It seems like the danger of extinction goes down dramatically, and the chance of the civilization, in one form or another, continuing for a long time (millions or billions of years), is much higher.


  2. They estimated the closest such civilization was 17,000 light years distant. So, to communicate our existence (once!) would require a 34,000 year process. I guess I have to point out that our civilization is roughly 5500 years old and it doesn’t look like we have another 5500 years in us.

    So, basically, all of those civilizations are too far away to be considered contemporaneous with us. In other words their existence is irrelevant to us. Unless … unless we invent a wormhole space drive … or a warp space drive … and figure out how to control our population … and solve climate change and soil depletion and … and…. See, there is hope!

    Liked by 2 people

  3. Would all intelligent organisms create technological civilizations? Would all the technological civilizations decide to explore the cosmos? We have a very anthropocentric view of how intelligence or civilization might develop on other planets.

    Liked by 1 person

      1. I wouldn’t consider 36 abundant. And not only do they have to be technological and want to explore the cosmos but actually would need to reach a state of technology to make it reasonable to do so. We are not even at the point.


        1. Under their assumptions, 36 is the number that currently exists, but there would have been hundreds of thousands throughout the life of the galaxy. If only a minute portion of that number is interested in exploration, and if it’s at all feasible, then at least a few should have succeeded.


          1. So many anthropocentric assumptions.

            If they decided to explore, would they explore as we do? Maybe they would only be interested in systems with certain solar characteristics or resources and aren’t interested in other civilizations? Would they be detectable by us? Would they hide from us and everyone else? Would their spacecraft be like an octopus blending into the ocean floor?

            Are there dead zones in the galaxy that make it difficult for a civilization expand across? Perhaps the other side of the galaxy is teeming with civilizations and we’re in a backwater.


          2. I think the biggest anthropocentric assumption is that a civilization producing intelligence is the inevitable result of evolution. You seem to want a certain amount of anthropocentrism, but not too much, just the right amount to preserve a particular notion.

            If we dispense with all anthropocentricism, we probably have a galaxy teeming with life, but one where complex life is rare, and intelligent life very rare.


  4. I saw the article, laughed, and shook my head. A simple odds calculation suggests we might be the only intelligent life in the visible universe (and are almost certainly the only intelligent life in this galaxy).

    It all depends on how likely it is for intelligent life to arise, and with an N of only one, everyone is just guessing.

    36 civilizations in the galaxy? Okay, sure. Call me when one of them shows up.

    Liked by 1 person

    1. Yeah, when I posted this, everyone seemed to just be sharing the new story without comment. But apparently lots of people were also annoyed by the clueless assumptions in the paper. I saw plenty of negative reviews today.

      We do have an N of only one, although I read something a while back that when all you have is a single case and an unknown population, there is a rough probability of 75% that it’s representative. (Of course, that means there’s a 25% chance it’s an outlier.) But I think the lack of any evidence for Earth having ever been colonized also counts as a major data point.

      There was a much starker analysis a couple of weeks ago that I only tweeted, because it was far more plausible.
      The tl;dr is that we’re probably the first intelligent species in the galaxy, and if we succeed in spreading, we’ll probably be the last, since we probably won’t allow another intelligent species to evolve (not necessarily intentionally). Unless of course we start uplifting things.


      1. “…when all you have is a single case and an unknown population, there is a rough probability of 75% that it’s representative.”

        I think that might only apply if the population has a Gaussian distribution. That wouldn’t be the case here — the distribution (I think) would be more like a reverse exponential curve of some kind. If the X-axis is degree of intelligence, the Y-axis would be large near zero and drop exponentially as intelligence increased. In that sense we’re at the far end of the distribution, not the center.

        As you say, Fermi’s Paradox seems suggestive. A rare case of absence of evidence having some probative value.

        I agree with the starker analysis. Any species that colonized the galaxy would probably prevent others from competing. Unless someone shows up fairly soon to stop us…

        As I’ve mentioned before, it’s really early days in the universe. I did the math once, and IIRC, if we say the universe will be viable for one-trillion years, and call that a 24-hour day, then we’re in the first twenty minutes.

        Given that one-trillion is probably a very conservative estimate, we’re even earlier than that. There likely haven’t been enough multi-billion-year-old life-sustaining planets for more than one of them to produce intelligent life. We may, in fact, have seriously beaten the odds. We’re the ancestors!

        Liked by 2 people

      2. I want to take issue with this statement: “ … we’ll probably be the last, since we probably won’t allow another intelligent species to evolve (not necessarily intentionally).”

        Assuming those who think we are the first, and we’ll expand into the galaxy are correct, what do you think will happen if we find a planet with advanced animal life? [I’m going to assume no technological life, yet, for the reasons we’ve been discussing.] Do you think we would just exploit it, or would we set up observatories?

        I know people like to give ants as paradigms, as in, if we want to build a highway we don’t worry about the ants we would destroy in the process. But in fact, if there was an interesting species of ant, and building that highway would destroy that entire species, we would probably go out of our way to not do that. People usually bring up this concept when worrying about how the post-singularity super intelligence will treat us, but the answer is the same. Any intelligence would be much more interested in preserving found life than destroying it. And it will be those superintelligent robots that spread out into the galaxy first.

        So I don’t see any problem with allowing intelligent and technological life to develop on such found planets. It’s unlikely (impossible?) they would become a threat.

        [and no, I don’t think we would be interested or able to hide the fact that we’re already all over the galaxy.]


        1. On preserving ant species, it’s worth noting that restraining development to protect species is a very recent practice, one that much of the world doesn’t necessarily follow.

          But more broadly, our very presence in their ecology would alter the dynamics. The intelligence niche would be filled. For another species to claim it, we’d have to first recognize their developing intelligence, and cede it to them. Would we do that? Consistently across the necessary time spans?

          Of course, as I noted above, that’s assuming we don’t recognize their development, go “Cool!”, and then accelerate it to see what happens.


          1. [dons philosopher hat]

            So here we get into morality/ethics. What should we do when … . I think there is a direction of improving morality towards more cooperation and less competition. Eukaryotes formed when a few prokaryotes started cooperating. Multicellular life formed when a few eukaryotes started cooperating. Social animals developed when individuals started cooperating in favor of their families.

            At each level, there is competition among those at the same level, but we see a group within the level overcome that competition and reach a new level. But now, for us, the competition and levels happen faster, with cultural evolution. And the direction towards cooperation continues when we start recognizing rights in other species. We create laws against cruelty to animals. We go out of our way to preserve species. I see no reason this direction won’t continue into our robot creations.

            So when you talk about niches being filled, and other species claiming niches, that’s competition talk. On the other hand, accelerating intelligence in other species might be a form of cooperation, so, maybe. I wouldn’t mind getting cool stuff from alien robot overlords.



          2. What we ought to do is complicated, and there’s no guarantee we’ll always arrive at the same answers across vast periods of time.

            But I think the thing to remember, is that the evolutionary processes that develop intelligence can be brutal. We might interrupt such development simply by removing the survival pressures from a species, or unwittingly altering them. Our motivations could be completely altruistic. And the results for individual members of the species may be beneficial. But what’s beneficial for them may not be what’s necessary for their descendants evolving more intelligence.

            On uplifting, an interesting question is whether such a species would thank us, or regard us as the serpent in the Garden of Eden.


Your thoughts?

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.