How will population grow, once we include whole brain emulations, sentient artificial general intelligences, uplifted animals, and similar entities to our all too human population mix, and none of them is very likely to die from natural causes? That’s not easy to tell, especially since the birthrate of humans has been falling in affluent countries for while a few decades. Let’s start with considering the different factors that would most likely influence population size. For the sake of simplicity, let’s assume that it’s the year 2100, or 2200, and that posthumans have developed all the fancy technologies needed to make everything mentioned here work out.
The following factors should increase population growth.
The miracle of biological immortality increases growth rate by reducing death rate to almost zero. When diseases and aging stop killing people, then population won’t readily decrease by natural means.
More space in space
Earth might become a bit cramped, if population increases by a couple of orders of magnitude, but that’s what space is good for: There’s more space in space. We could colonize other planets, or better create artificial habitats in space. A Dyson swarm can provide living space for at least a billion times more people than Earth can. Add another 9 orders of magnitude, or more, if we transition towards full virtual population in a Matrioshka brain. Add 100 billion times more, if you colonize the whole galaxy. And don’t stop there. The universe is big. This sets the stage for truly enormous population sizes. But let’s focus on one single star system at a time, since those are fairly natural “habitat units”, due to the huge distances between them.
Depending on the kind of technology you use, and the kind of animals you want to uplift, you’d get a couple of billion persons more (for pets and large animals), or trillions of billions, if you go crazy and decide to uplift insets to fully fledged members of society. It’s hard to tell why anyone would do that, rather than “simply” connecting the whole biosphere to a biosphere god AI, but it’s a theoretical possibility.
The ability to grow babies outside of human bodies from the start could become a trigger for creating a lot more humans that way, than people would naturally want to, especially when combined with the next point. Combining this in vitro fertilization reduces reproduction to the collection of germ cells, their combination, and the technological growth of the newly created person. People might also want to modify or create germ cells artificially, so creation of new humans might be akin to selecting desired genetic traits in an app and then click on “create”.
Raising kids might become cheap
Why not let robots do the job of raising children? I mean robots that look and act like the perfect human parents. At that stage those robot parents would count to the sapient population, too, but it might be argued that robots would be at least slightly cheaper to (re)produce with sufficiently advanced technology. And if the robots themselves don’t want to do the job, then kids could be raised in a gamified virtual reality environment with minimal external effort. Food won’t be much of a limiting factor, either. Synthesizing nutrients chemically or biologically will most likely become quite trivial in the future.
Copy and paste
When it comes to AGI minds, or whole brain emulations, it should be easy to copy their mind data to other computational units. The limiting factor is then the number of computational units available.
3d printing of new bodies
Bodies and computational units could be 3d printed on demand. With mature technology, that process will be fast and efficient. Only the availability of matter, energy, and 3d printers would be limiting factors then.
Self-replicating 3d printers
When you think that 3d printers might be relatively rare, you haven’t consider the option that 3d printers could print more 3d printers. That should be a pretty fast exponential process, even if it requires some robot assistance. Alternatively, you could make 3d printers, bodies, or computational units out of small self-replicating nanomachines, kinda like most biological stuff is made out of cells (that do have this self-replication trick figured out).
When running simulations that include sentient minds on their own, you could just transfer those minds to the “real world”. If a civilization runs billions of ancestor simulations (or alternate history simulations, or simulations of life emerging on alien planets, etc.), each with complete whole brain emulations of humans, you get a huge total population. And if the citizens of the future decide to play virtual reality games that include sentient simulated persons in their own right, and those are then transferred to the “real world” after the game is over, then you’ve got even more persons populating your computronium.
Storing backups of whole persons on data storage devices should be possible, too. Just for the case that something unlucky happens that kills a person. With this kind of technology, death will be pretty much abolished. And you could even animate old backups from decades before, just to see how your old version of you will handle with their relative future.
Population growth could be extremely explosive in the future, if all you have to do, is basically snap your fingers and let the almost magical automation do the trick of generating new persons on demand. The old hard limiting factor is how quickly you can collect matter and energy and turn them into new self-replicating machinery. If this time decreases exponentially, you get doubly exponential growth of the population. At least until you reach technological limits. But even if your total technology base self-replication time will come to rest at a large number like a year, it will only take 30 years to increase total population by a factor of a billion. At that point, it would take less than 100 years to build and populate a matrioshka brain completely. But even if that turns out to be technologically possible, it doesn’t mean that we will do that.
Now let’s come to the factors that would limit growth of the population.
If people decide that they need lots of backups, for all the past versions of themselves, then that’s a lot more storage space used for backups than for actual people. Depending on how many backups people desire, that could reduce the maximum population by a couple of orders of magnitude.
Lack of reasons to procreate
If people live indefinitely and quality of life is extraordinarily good as it is, there might be little motivation to create new persons. But of course, we shouldn’t bet on that being true. People are often fond of children. Or they might want to have more persons to get more work done, and more culture produced. Having more people is usually better. So, this point of lacking motivation may be one of the weakest on the “against growth” side.
Higher quality and quantity child care
Having more persons care for children, for longer spans of time, might be a good idea, for various reasons. If people decide to go that route, instead of the “quick and cheap” mode of child raising and education, it will obviously take more time to get the next generation up to speed. This would slow the rate of growth of the part of the population that chooses this life style.
People want to preserve their material wealth
Perhaps materialism will be very important to people in the future. The ability to have a huge starship for yourself (or be a huge starship) might be valued higher than the amount of culture that would be produced by a larger population. This doesn’t seem to be all too likely, though, since all that material wealth could be simulated, too, and it’s hardly inferior, if it’s simulated rightly. The real limitation might come when the population density is so high that even high quality simulations become relatively expensive. As rough estimate, this point may be reached when computational power used for simulated environmental stuff is about 10 times higher than computational power used for virtual people. We’d get a factor reducing maximum population count by an order of magnitude, similar to the effect of backups. In fact, we can add up both into one factor of “non-active-people” computation/storage resources. Those will most likely reduce the maximum reasonable population number by a factor between 10 and 1000.
Since it’s technically very easy to create new persons, and people will probably want to live in a world in which they have rights, it is to be expected that generating new persons will be something that’s highly regulated. Population growth would be limited by legal means. In any case, allowing every person to create a million copies of themselves will quickly use up all natural resources. If that happened, people could consider copies as pests and probably opt for deleting them, and the offending original permanently. There doesn’t seem to be a long-term viable option other than have strict requirements on the creation of new persons. Who will have the right to generate new persons will probably be a huge political issue. In the most extreme case, there might be a complete moratorium on creating new persons until those political conflicts are resolved.
We don’t know how people will think when they live thousands, millions, or billions of (subjective) years. Persons they will reach the point at which they “have perceived enough”, and will opt to shut themselves down permanently. On the other hand, why not simply erase parts of your memory and explore interesting stuff again? Perhaps the most plausible reason to commit suicide would be the altruistic motive to make space for new life to experience the world in fresh ways. However, that would do nothing to change the total population number. Instead, it would simply modify the “composition” of that population.
Merging multiple minds into one, may be the only plausible way of decreasing the population. However, this probably won’t happen very often. And even if it does, the vacant space for new life will quickly be filled up.
Maximum population number will most likely be reduced by an “extranoetic factor” that summarizes computation and memory resources required for backups and high quality (simulated) environments and possessions per person. While this factor might reasonable be guessed to be between 10 and 1000, it could as well lie between 1.001 and a billion. The only factor that might effectively slow down population growth is effectively enforced legal restriction of creating new persons. Perhaps it’s the biggest current unknown how that political population growth limitation would work out. Since it’s the easiest to create new persons by copying existing ones, or by creating characters in simulated worlds, it is to be expected, that the majority of individuals will be of that type: Copies or simulations. That may not be a politically desired outcome, in which case copying or simulating persons would be nearly, or completely, outlawed. If such a prohibition could be effectively enforced, population growth might be closer to the doubling every 20 years than doubling every year. Perhaps population doubling time will vary dramatically based on the current political climate.
Thus, my final conclusion is that the most important factor for determining population growth, given posthuman technology levels, is politically motivated limitation of population growth. Before you reject that conclusion as unrealistic, you should consider that a failure to limit explosive population growth of certain factions will likely give rise to extremely destructive (civil) wars.
What are your thoughts on this matter? What kind of population growth, or final population size (per average star system, or planet) would you prefer?