Cross-posted from Telescopic Turnip.

In his recent review of Lifespan, Scott Alexander writes:

Algernon’s Law says there shouldn’t be easy gains in biology. Your body is the product of millions of years of evolution – it would be weird if some drug could make you stronger, faster, and smarter. Why didn’t the body just evolve to secrete that drug itself?

He is talking about anti-aging research, and wondering why, if there is an easy way to stop aging, humans haven’t already evolved immortality spontaneously. There are many relevant things to say about this, but I think the evolutionary perspective is particularly interesting. Under some circumstances, it might be that immortality is inherently unstable.

The Imperium and the Horde

Suppose that it’s the future, and the FDA just approved a pill that makes you immortal. Of course people disagree about whether one should take the pill or not. As a result, humanity is now divided in two populations: the Immortal Imperium, who took the immortality pill, and the Horde of Death, who still experience the painful decay and death we all know and love.

Artist depiction of the Horde of Death.

So, people from the Horde spend their time having plenty of children to populate the next generation, while people in the Immortal Imperium try to escape their existential ennui by reading speculative blog posts on the Internet. Who will prevail?

Two orders of fitness

There are two competing phenomena at play here. One is first-order selection, which is how many of your genes are passed on to the next generation, the more the better. For the Horde of Death, there is nothing mysterious: they reproduce, then they die, and an uncertain fraction of their genes gets passed on.

What about immortal people? They don’t really pass anything to the next generation, because they don’t do the whole generation thing. On the other hand, all of their genes will still be around centuries after centuries, so for the genes involved, this is a 100% success rate. In this sense, people in the Immortal Imperium have a very high first-order fitness.

The second process is second-order selection. This is selection on evolvability. This is about how easy it is for your lineage to improve its own first-order fitness in the future. If a lineage finds a way to evolve quicker, then it may eventually take over the whole population because it will be more likely to discover new beneficial variants, and the original mechanism that granted better evolvability will hitchhike with these new variants.

If you want to see it happen with your own eyes, look at Richard Lenski’s long term evolution experiment, where people have been growing the same E. coli lineages continuously since 1988. Among the mutants that took over the population after a few thousands of generations, some were present since almost the very beginning. They are called EW, for Eventual Winners. Other mutants from the same period eventually disappeared, so they are called Eventual Losers (EL). Surprisingly, in the early days, the EL were able to grow faster than the EW. But in the long term, the EW did better. That is because the EW had mutations that made them more evolvable: they became more likely to acquire further beneficial mutations that ultimately made them grow faster than the EL. People in Lenski’s lab replayed the competition over and over, and most of the time the more evolvable strain ended up taking over.

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From Woods et al., 2011. EL: eventual losers. EW: eventual winners.

Second-order selection matters most for organisms that are not well-adapted to their environment. After all, if you are already at the top of the fitness landscape, there is no point improving your gradient-climbing abilities. Intuitively, it may look like humans are well-adapted to their environment, because we deliberately modified our environment to match our needs. But in a biological sense, current mortal humans are absolutely not well-adapted to their environment. In the First World, fertility is at an all-time low, yet we have all the resources we would need to have tons of offspring. In terms of sheer gene-copying, there is clearly a lot of room for improvement. In fact, there is a lot of genomic evidence that humans are currently under high selective pressure.

(Here is a fun way to think about it: consider that contraceptives are basically antibiotics for humans, in that they are chemicals that prevent us from reproducing. What do bacteria do when exposed to antibiotics for a long time? They evolve antibiotic resistance. So if someone gets a mutation that makes them resistant to contraceptives, they will have a fitness advantage. Realistically, we would quickly notice and switch to other contraceptives, so it’s not likely to be a large issue. But what if people get mutations that increase their parental instinct instead?)

Will the Horde win in the long run?

While the Imperium has better first-order fitness, they are pretty bad at evolving. It is likely that they’ll stop having children to avoid over-crowding. In that case, they just stop evolving completely.

Zardoz Is The 70s Sci-Fi Movie Sean Connery Wants You To ...
If I remember well, that’s what the immortals in Zardoz do. That’s enough evidence for me.

Meanwhile, the Horde does a full cycle of variation/selection/reproduction every 30 years or so. This makes them pretty effective at discovering beneficial variants and become more adapted. To makes things worse, humans have a tendency to constantly change and remodel their own environment. This would explain why the rate of human evolution became higher in the last few thousands years: civilization is changing all the time. Our genomes are always adjusting to human-made changes in technology, environment, agriculture and social organization. The Horde would have no problem finding new genomes to stay up-to-date. The Imperium must do with the same old genomes they have had since the late 21st-century. For example, it’s easy to imagine that the mortals can physically adapt to global warming, while the immortals will not have this chance.

If the Immortals do continue to have babies, their second-order fitness is still pretty bad: if the centuries-old generations still reproduce or mate with the newer generations, the average generation time is still much longer than the Horde’s, so they still evolve slower, and it only gets worse as the population ages. Also, the original immortals still have to compete for resources with the younger, better-adapted immortals, so we are back to the problems we had with the Horde.

Cultural evolution

Anyways, genomic evolution is only one part of the picture. There is also cultural evolution, which is how cultures with higher fitness reproduce (or spread) faster, selecting for more adapted cultural norms. The main reason why humans are so good at colonizing everything is that cultural evolution is faster and more efficient than genetic evolution, so that’s an important thing to have.

For the Horde of Death vs Immortal Imperium conflict, I am not sure who would benefit more from cultural evolution. On one hand, the Imperium has a lot of experience. They have seen everything and had plenty of time to discuss every problem. They have all read the Sequences. They have maximum wisdom.

On the other hand, the Horde gets fresh brains. We all know that young scientists and mathematicians tend to do the most groundbreaking discoveries, and that scientific fields tend to have booms in creativity following the death of established leaders. So what happens if they never die?

Here is a hint of evidence from tennis: when composite rackets were introduced, it altered the way people play in a subtle way, so that the previous way to play was no longer optimal. According to that one study, older players had trouble adapting to the new way to play, which favored younger players. I don’t know how well it generalizes – at the very least, it implies that the Imperium would suck at tennis.

Another hint of evidence: moral values seem to be acquired at young age. When asked moral dilemmas (is it ok to eat the corpse of your pet after it was killed by a car?), people are more morally conservative when the question is asked in their native language, as opposed to another language they learned later in life. This suggests that some of our beliefs and values are shaped by the things we learn while our brains are still developing, and it is not clear whether that can ever be fully overwritten. Perhaps it will be much more difficult for the Imperium to update to new moral norms, which would hinder their cultural evolution. If the Overton window remains stuck in the same place, it would also hamper technological progress: at some point, the Immortals will see all the new gadgets the Horde constantly comes up with, and of course find them absolutely disgusting and immoral.

Elephants and mice

Altogether, it is hard to tell how humanity would continue its evolution if we discovered a way to immortality. There is a decent chance that an immortal population is inherently unstable, but there could also be cultural workarounds. One possible path that I didn’t explore is that mortals and immortals end up occupying different ecological niches. Elephants are practically immortal compared to mice, yet both of them coexist without out-competing each other. If the Horde and the Imperium ever reach such an equilibrium, what would their respective niches look like?

One last quirk: what if the Immortal Imperium, in a last-resort strategy, decides to put immortality drugs in the Horde’s drinking water? Then the Horde become immortal too, and lose their second-order advantage. Problem solved. Unless, of course, people start developing resistance to the immortality pills – such a mutation would be selected for because it helps selecting for mutations that help selecting for mutations that are beneficial. I have never heard of any third-order selection occurring in nature, but maybe humans will make it happen.


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47 comments, sorted by Click to highlight new comments since: Today at 4:34 AM

You might appreciate thinking about the red queen model of evolution and its' impact on your arguments. The technique of randomization of the genome as a way to avoid parasitism being lost by the immortals is probably an extremely serious problem in the long term. If as a parasite, your target organism is immortal, you have a long time to adapt, kind of like parasites adapted to bananas (which reproduce asexually).

That's a very good point, I didn't think of that (I was kind of assuming that the immortals just cannot die, which is of course unrealistic as Donald Hobson pointed out).

Even ruling out death and disease, couldn't the 'horde' also evolve to perform some sort of 'social parasitism'?

Thanks for writing!

One trend in longevity-enhanced cultures which I expect to become common, is for "old and worn-out souls" to trigger a kind of mental rejuvenation: Use some type of medicine/gene-activation/.. to trigger a softer version of what happens during childhood.

I see several reasons:

  1. This would allow for a culturally-acceptable and powerful method for people to reinvent themselves and start anew (possibly with an agreement that the usual date is every 100th birthday), which would be a more important element to cultures suitable to longer life-spans.
  2. Also (depending on how the immortality works), I would assume that people would wish to have the ability to reinvigorate their "passions of the past". I think it is quite common that older people lose many of their interests and replace them with "their legacy" and "watching the young ones". If this isn't directly inhibited by the life-extension, a method to reduce or revert this change would become important.
  3. I don't know enough about this to be sure, but I'd be surprised if our brains operate in a way that does not in some sense accumulate brittleness (weak enough that it typically isn't important for current(/past?) lifespans). Finding a way to stabilise this would be important and "just hit restart" seems like a plausibly helpful and achievable approach.

I think that this would change the dynamics described in the OP quite a bit, as the cultural dynamics (exploration) could stay quite strong. Also, this might weaken the forces that create a gap between longevity-enhanced and normal-longevity people.

This is what psychedelics do, especially high doses.

Mental rejuvenation would solve some of the issues. But what is this supposed to be specifically? Increased memory consolidation or some kind of amnesia? What about habits and motor memory? Without more elaboration, it amounts to hand-waving. Also, the body wouldn't adapt to the environment, e.g. new foods. Positing additional drugs for 'reprogramming the body' might help but again what would they do? You can of course stack fixes on fixes with drugs. I'm not sure how this compares to regular evolution.

Good points!

But what is this supposed to be specifically?

  My estimate of what could plausibly be achieved in the near future is my model of "the thing that happens during childhood", maybe with better control by the individuum. This would be some phases of heightened learning rate/'priority' for different parts of our mind (fear and recognizing safe/unsafe situations; calibrating and exploring perception and motion; status and norms; sexuality; sense of self and identity; ...). I assume that this 'emotional rejuvenation' could work relatively well 'for a few rounds' even with relatively crude methods. As dkirmani notes, psychedelics do have effects that seem related. But for things like memory or systematically replacing old/mortal neurons, this would likely not suffice.

Interesting. It's hard to imagine the new markets opened by anti-aging. That being said, if such a drug existed I would probably take it regularly even if I'm not immortal. Now I wonder if that would be possible to do without erasing your memories. Otherwise, it would defeat the point of immortality.

See the story, "Good-bye, Robinson Crusoe", by John Varley.

Your assumption that the immortals all choose not to reproduce is unrealistic. (for an evolutionary equilibrium) Either 1) Nothing can kill them, nothing can stop them reproducing. Exponentially expanding ball of flesh, stopped from collapsing into a black hole by shear imortality.

2) Absolutely unkillable, need some resource to reproduce. That resource is the bottleneck.

3) Can die of something sometimes. Malthusian equilibrium. The more stuff they can't die of, the better they do compared to the "mortals".

The winning strategy is to take the immortality pill and reproduce. Voluntarily stopping having children to prevent over-crowding only works if everybody does it.

He addresses this in the section "If the Immortals do continue to have babies, their second-order fitness is still pretty bad".

Doesn't matter. Taking the immortality pill grants a strict competitive advantage over people who don't take it.

The OP is not arguing on the individual level but on the population level. It is not uncommon that populations evolve to extinction. 

It seems that this post is describing the regime beyond the threshold where group advantages outweigh individual advantages.

Several things about this post are unclear or don't make much sense to me.

What do you mean by "immortal"? 

You seem to be responding to the question, "Why didn’t the body just evolve to secrete that [ immortality ] drug itself?" That would imply that "immortality" doesn't really mean that death is impossible, just that you don't age.  (It's obvious why absolute immortality can't evolve.) You could still die from starvation, predation, homicide, war, some sufficiently aggressive disease, some sufficiently severe accident, etc.  But much of what you write seems to make no sense once one acknowledges that everyone is still going to die sooner or later, even if later is much later.

I'm also not clear on why the not-really-immortals wouldn't have children.  Indeed, why not just as many children as those who choose not be to immortal? And actually, they could have many, many more children.

You also seem to assume that the not-really-immortals live separately from the mortals.  But why?  The scenario would seem to be that a drug that prevents aging is discovered.  Some people then choose to take it.  Some don't.  I don't see how they end up in different societies.

Considering all this, I don't see why the decision to take the anti-aging drug is not strictly better from an inclusive fitness point of view.  (You can still decide to give your share of food to your children if there's not enough to go around...)

Sorry if things are not clear. The way I look at it is through the number of generations, which directly determines the evolution rate.

  • The mortals do one generation every 20-40 years or so
  • The immortals do much fewer generations: either they don't reproduce, or they do but then the average age at which they have children is much higher. If you have a child at 10,000 years old, your child (and yourself) will live in the same world as humans who underwent 10,000 years of natural selection.

This is all assuming all those people compete for a shared pool of resources. In the long run, that might make the immortals more likely to die of accidental causes (or diseases due to elevated temperatures, or new viruses etc.). If immortals decide to have children only when they are young, and then stop, then I agree my point doesn't really apply.

For the second point, it's not necessary that they live separately (talking about an Imperium may be a bit misleading, sorry). In fact, the more competition, the harder for the immortals to keep up.

I'm still not following you.  If the "immortals" start having children at age 20, and have one every 5 years or so for about the next 1000 years (the average age when they get hit by a bus, or whatever), for a total of about 200 children, why isn't this much better from an evolutionary point of view than being a mortal, who has maybe 10 children?

Sure, the average age at which the immortals have children is much higher. But why does that matter, when they have children at a young age, just like the mortals?  They have everything the mortals have, plus more.

Of course, this isn't sustainable - something will put a stop to it, such as famine.  But then, any species that isn't a total failure cannot sustain its maximum ("when times are good") reproductive rate.  (If its maximum reproduction rate is bare replacement, it won't be able to recover from some setback, a hurricane or whatever.) If one assumes that "immortality" is cost-free (eg, it doesn't lead to reduced muscle mass, hence reduced strength, and greater chance of losing a fight), it seems like a definite evolutionary advantage.

I think he is addressing this in the section "Will the Horde win in the long run?" Which point do you disagree with?

There are lot of unstated assumptions involved here.  Let's assume that the tendency to take the anti-aging drug is hereditary - so we're really discussing whether or not selection will favour the gene for doing this.  If the mortals and "immortals" (who actually die after ca. 1000 years) are not reproductively isolated, then it seems quite clear that the gene for taking the drug will be favoured by selection.  If one assumes reproductive isolation (as the post seems to), perhaps for social reasons, but that the two groups compete for resources, then the immortal group loses out only if their higher reproductive capacity is outweighed by worse adaptation to changing circumstances. Whether the "immortals" would be less-well adapted will depend on selection effects within that group - if the young immortals out-compete the older immortals, then they adapt just as fast as the mortals.  I think you would have a difficult (but maybe not impossible) time finding values for the various within and between group selection effects that would produce a rapid-adaptation advantage for the mortals that would outweigh the huge reproductive advantage of the immortals.

The whole scenario seems rather far from reality to me - talking about evolution implies selection - ie, death or infertility. Assuming the anti-aging drug does not directly affect fertility, I think one can assume that any behavioural trait of low fertility among the immortals will be strongly selected against, after which we're in the Malthusian state in which the "immortals" often die early from starvation.  So the average age  when they have children may not be so high after all...

Plus, of course, the scenario assumes a world-changing innovation of an anti-aging drug, but no other world-changing innovations (AI, space travel, ...?) that would render the whole discussion irrelevant.

I think I get what you mean by "They have everything the mortals have, plus more" now. The key part is the "200 children" which is of course not sustainable and the answer you and OP have depends on the implicit assumptions of how that is handled.

Is there perhaps an unjustified assumption implicit here that somehow immortality implies some level of evolutionary fixed point position? Why wouldn't the pill actually produce an organism that is both in a very stable health equilibrium in stable environments but rapidly able to react to changes correctly?

That might be the story behind the experimental results. The EL group is very well suited to the current environment but unable to adapt to the new later environment while the EW do adapt. Here it seems very much the niche specialist versus the more generalist. Generalists, that are at least able to survive seem to last longer than the niche player.

I don't think there was so much change in the environment in Lenski's experiment (they are always using the same medium, but the environment may still change because of the organisms inside it evolve). But it's true that immortality could make people more resistant just because they have young bodies, or some other side-effect reason. That is the case where first-order fitness is large enough to prevail over second-order. I don't see why the immortality pill would have such a strong effect, though.

I think cultural evolution will be the greater factor by a large margin. I think the technology for immortality is possible but that it will either directly involve genetic engineering of living humans, or be one or two steps away from it. People who are willing to take an immortality drug are very likely to also be willing to improve themselves in other ways. If the Horde is somehow going to outcompete them due entirely to beneficial mutations, the Imperium could simply steal them.

Genetic engineering of living beings would be a way out. Somewhat like self-modifying code. But without further elaboration of what it is supposed to mean or how it could work it's handwaving.

What I meant is changing the genetic code in ~all of the cells in a human body. Or some sort of genetic engineering which has the same effect as that.

Here's one model I have as to how you could genetically engineer a living human:

Many viruses are able to reverse-transcribe RNA to DNA and insert that DNA into cells. This causes a lot of problems for cells, but there are (probably) large regions of the genome where insertions of new DNA wouldn't cause problems. I don't think it would be difficult to target insertion of DNA to those regions, as DNA binding proteins could be attached to DNA insertion proteins.

This sort of technology requires only the insertion of RNA into a cell. There are a number of ways to put RNA into cells at the moment, such as "edited" viruses, lipid droplets, and more might be developed.

I also believe targeting somatic stem cells for modification via cell-specific surface proteins is possible. If not we could also cause the modified cells to revert to stem cells (by causing them to express Yamanaka Factors etc.).

The stem cells will differentiate and eventually replace (almost all) unmodified cells.

The resulting technology would allow arbitrary insertion of genetic code into most somatic cells (neurons might not be direct targets but perhaps engineering of glia or whatever could do them). Using CRISPR-like technologies rather than reverse transcription we could also do arbitrary mutation, gene knockout, etc.

I guess this is still somewhat handwavey. Speculating on future technology is always handwavey. 

I guess this is still somewhat handwavey. 

No, it is fine. It clarifies what you have in mind and some ideas on how to achieve it, and it allows to elaborate on it or refute it. 

I think it won't be easy to modify the genome of individuals to achieve predictable outcomes even if you get the machinery you describe to work. 

I think it won't be easy to modify the genome of individuals to achieve predictable outcomes even if you get the machinery you describe to work. 

Is this because of factors like the almost-infinite number of interactions between different genes, such that even with a hypothetical magic technology to arbitrarily and perfectly change the DNA in every cell in the body, it wouldn't be possible to predict the outcome of such a change? Or is it because you don't think that any machinery will ever be precise enough to make this work well enough? Or some other issue entirely?

I think this should also link to the two headed bacterium post since the immortals here are like persisters.

I'm not sure I understand what you mean. The advantage of persisters is that they resist chemicals that target cell growth, so the human equivalent would be, for example, that a factory accident contaminates all the drinking water with potent contraceptive. In that case, maybe the mortals would go extinct and only the immortals would survive. But that doesn't seem very likely.

Immortals would be incentivized to invest in mitigations that don't make any sense for mortals because they only kill you once every 1000 or more years.

To be practically immortal, an entity must possess the following qualities:

  • a) it must be distributed across many semi-autonomous nodes; killing some nodes should not cause the death of the entity itself
  • b) the nodes must be distributed across vast distances; no natural disaster should be able to kill all the nodes
  • c) the entity should be able to create its own backups, hidden in many remote places; no system-level sickness of the whole entity should stop it from being restored from backups
  • d) the entity should be able to rapidly self-improve itself, to win against intelligent adversaries

If we consider only biological entities, the supercolony of ants in Southern Europe is the closest to being immortal. It consists of billions of semi-autonomous nodes distributed across a 6 000 km stretch of land. Of course, it still doesn't possess all the 4 qualities, and thus is still mortal. 

Although humans consist of individual nodes too, the described path to biological immortality was closed for them a long time ago. There is no way for the natural selection to take a human and gradually convert him into something like an ant colony. 

And that's the main reason why humans are not immortal (yet): our monkey bodies are not designed for immortality, and cannot be redesigned for that by the natural selection. 

On the other hand, mind uploading could give us all the qualities of immortality, as listed above. 

An entity with the described qualities cannot be outcompeted by your "Horde of Death", as the entity can simply sit and wait until the Horde becomes extinct, which is inevitable for all biological species. 

Thus, immortality is the final aromorphosis. Nothing can outcompete immortality.

None of this is sufficient to survive the heat death of the universe.

As a wise man pointed out:

The fate of the universe is a decision yet to be made, one which we will intelligently consider when the time is right

Our current understanding of physics is so ridiculously incomplete, it is safe to assume that every single law suggestion of physics eventually will be modified or discarded, in the same way as the theories of phlogiston, life force, and luminiferous aether were discarded. 

After we gain a sufficient understanding of physics, we will see if the heat death is still a threat, and if yes, what tech we should build to prevent it.

Artist depiction of the Horde of Death.

Broken link.

Fixed, thank you.

If we were to become immortal, assuming people wanted to, everyone could eventually become a master in every subject, so would it not be safe to assume we would find ways to change our genomes in response to changes?

I agree, though it depends on whether rational design of genomes is even possible, and can do at least as well as natural selection. Can we ever come up with something like an ATP synthase? (Tbh, just maximizing the traits we know about may be enough to stay in the game for a while)

This also brings into question "Ship of Theseus". If we were to genetically modify all our cells, would we still be us? Who/What are we? Am I the same person that went to sleep or am I a new person with the same memories?

For a good paper on this topic, I have to recommend Werfel et al. 2017:

They make a spatial model of a world where resources replenish at a fixed rate and show that mortal populations outcompete immortal populations by improving their children's fitness, as there are fewer mass starvation events. 

Why do you assume the immortal population wouldn't (at least within a few centuries if not right away) obtain sufficient genetic engineering competency to modify existing beings in accordance with whatever changes they thought would benefit them as individuals or a collective? Or nanotech to simply put their bodies in whatever state, form whatever assembly of molecules, they need to match whatever mutations they see the Horde evolving? And in the event that there is no actual Horde because everyone becomes immortal, biological research can still continue to make advances.

I was also going to say something along the lines of what Korz wrote about mental rejuvenation, but I don't have much to add to what they said.

Happy to see immortality addressed in a much more focused form than my old A defense of Senexism (Deathism) post. 

Thanks for the link. I enjoyed the article, not sure why it was downvoted.

I think a lot of people in this community see death as one of the most important things to overcome. 

Epistemic status: shitpost

Second-Order selection against My Immortal