The Fermi Paradox asks why we have not yet encountered other intelligent life given the high chance of intelligent life emerging.

I recently had the following thought:

Evolution shapes the behaviour of an organism so that the organism behaves in ways that increase the organism's chance of survival.

When evolution created humans, it created a being that possessed general intelligence, or put another way, a Turing machine in its head.

We know from the halting problem that we cannot, in general, determine if a Turing machine will halt. In other words, the behaviour of Turing machines is, in general, unpredictable.

Since a human is a Turing machine, its behaviour is, in general, unpredictable. This means that evolution can no longer alter the human code in ways that are guaranteed or likely to work. Thus evolution can not longer "adapt" humans. As evolution can no longer reliably adapt humans to their environment, humans will go extinct.

In general, once life becomes intelligent, evolution loses control of it, and thus can no longer shape it to be adaptive.


1 Answer 1


I don't find this argument persuasive, but it sounds like a matter of opinion. I'm not sure this is a matter of computer science -- it sounds speculative and a matter of opinion to me.

I have a problem with the way the word "unpredictable" is used. The halting problem tells us that there is no algorithm that can always predict the outcome of a Turing machine. There might still be algorithms that can do so some of the time, or even most of the time. The halting problem only tells us that the algorithm cannot work 100% of the time, but it still remains possible that some algorithm might work 99% of the time.

I don't think it follows that evolution is unable to alter the human code in ways that are likely to work. Of course there are no guarantees, but evolution can still change us, and it's entirely consistent with everything we know about computer science that those changes might be more likely to be positive (specifically, enhance survival and reproduction) than negative.

There is plausible evidence of evolution affecting humans recently, and specifically in the period after humans have been able to think. For instance, it is plausible that there have been changes to malaria resistance, starch digestion, lactose digestion, eye color, skin color, hair color, hair shape, sweat glands, protection from disease, and more in the past few ten thousands of years. Whether or not this has actually happened, hopefully those examples point to a gap in your logic. It seems quite plausible that evolution could have changed us in those ways. I see no reason that the halting problem would render such evolutionary changes impossible.

Moreover, even if it were true that humans were unable to evolve further, I don't think it follows that humans would inevitably go extinct. For instance, I've read that some sharks and crocodiles seem to have been around for 80-150 million years, with few changes by evolution.

Ultimately, most of this does not appear to be a matter of computer science, so I'm not sure whether the question is appropriate here. Perhaps I should not have posted this answer.


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