We’ve all heard of the Fermi paradox. Simply put, it is the contradiction between the apparent ease of life emerging and the fact that we know of only one planet upon which it has occurred: Earth. In the words of Enrico Fermi, the physicist who gives his name to the paradox: “Where is everybody?”.

For years, a reasonable answer to the paradox has been to assume that the formation of life is an exceedingly improbable event and occurs so rarely in the universe, despite its immense scale, that the chance of two civilisations chancing upon one-another is very small.

Yet as we pull back the curtain on the biochemical processes that form the basic building blocks of life, we increasingly find that this is not the case: the chemical processes that may have bootstrapped life are not, in fact, particularly rare. This seems to fly in the face of this solution to the paradox, and so Fermi’s simple question continues to hang in the air like a bad smell.

There are other solutions, of course: perhaps the genesis of life is a relatively simple process, but that the development of intelligence, or civilisation, is not. But at this point we’re pushing the goalposts, engaging in a cat-and-mouse game of whataboutism.

Bias

A few months ago I watched an interesting video by David Kipping on the subject that makes a point I’ve not seen mentioned elsewhere: the very act of asking this question is subject to survivorship bias.

Kipping’s conclusion is based on the assumption that most goal-oriented agents converge on expansionary, colonial behaviour as a side-effect of maximising their goal (and those that don’t converge on this behaviour rapidly become an easy meal for those that do). Any contact with such a civilisation would represent a serious existential threat to humanity and would likely lead to our extinction. Therefore, for us to even be alive to ask the question “Where is everybody?” in the first place, we must necessarily already exist in a relatively quiet corner of the universe, free from expansionary civilisations.

For me, this is an entirely satisfactory answer to the paradox. The very fact that we exist, as cognizant observers, is evidence that we are out of reach of expansionary interstellar civilisations: not necessarily because life - or even intelligent life - is inherently rare, but because we won the existential lottery¹.

Time

If you’re observant, you’ll have noticed a worrying gotcha in the prior reasoning. Specifically, it doesn’t make any promises about the future. All that our survivorship bias shield gives us is confidence that life on earth has not come into contact with an expansionary civilisation in the past. It has nothing to say about the future, and indeed, we revert back to ‘vanilla’ survival odds when looking forward.

More interesting still is that we can transplant this reasoning to a wider set of scenarios. In fact, we can say that any event that would pose an existential risk to life on earth has not occurred, and so we have no basis for rationalising its likelihood of occurring in the future without studying the fundamentals of the phenomenon. This means that when making judgements about the future, we should be wary about being overly optimistic. In general:

We cannot draw conclusions about the likelihood of existential events by observing the past.

There’s a name for this: it’s called the anthropic principle, and it’s a surprisingly powerful tool for reasoning about the state of things around us, but also a terrifying source of reasoning bias when we attempt to make predictions about the future.

It means that statements like “The last asteroid impact that posed an existent threat to life on earth occurred 66 million years ago so we can expect to be safe from impacts for a similar length of time again” are inherently flawed. The fact that the last existentially threatening impact occurred 66 million years ago tells us exactly nothing about the chance of a future Chicxulub-scale event because a requirement for our own existence is that one has not occurred since, allowing the human race to come into being and reason about such things in the first place. Any observations we make about the world are implicitly constrained by the prior that we already exist and whatever must be true about the state of things for that constraint to be satisfied are true.

What this means is that we should be extremely mindful of the fact that existential threats may be much more likely than we’d prefer them to be, and that we should preemptively invest more time and resources into monitoring and preventing existential threats than history might otherwise imply is wise.

Here and now

Here are some possible existential threats that we should be on our guard about:

• Climate breakdown

• Pandemics

• Asteroid impacts

• Nuclear war

• Supply chain fragility

• Catastrophic loss of biodiversity

• Artificial superintelligence

The world is changing, fast. The past is not a guide to the future. Trying to apply the same reasoning to what lies ahead as we did to that which occurred before may very well be our downfall, and the anthropic principle should give us all pause for thought.

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1. An intiguing conclusion that falls out of this chain of reasoning is that we should expect to see the universe around us teeming with pre-interstellar life that poses little existential risk to us, should we develop the technology to effectively search for biosignatures. Let’s not mess things up by turning into an example of the aforementioned expansionist colonial civilisations. ↩︎