Rather than seeing the population as being made up of more-or-less copies of individuals, a different approach would be to see each individual, including yourself as a sum of various patterns, some of which are longer-lived than others; and many of which change over time.
By "yourself" here I mean "the you that is thinking this thought right now", not "the four-dimensional extent of your lifetime" or some such.
For instance, one of the patterns that is an ingredient in "me" is the human genome, and specifically my genome, including any hereditary quirks I've inherited from my specific ancestors. This persists through lifetimes and reproduction; and this explains certain facts about me — such as that I have memories of bodily senses such as hunger and sexual arousal, which contribute to my genome's survival; but also such as that I have ten fingers and ten toes, as is typical for a human.
Another of the patterns that is an ingredient in "me" is the English language. This persists through different mechanisms than my genome: the imitative tendencies of human children; the teaching tendencies of human adults; and the economics of the English-speaking nations being favorable to immigrants (such as my German-speaking ancestors) learning English. The fact that I am having these thoughts in English is not a consequence of my genome; it is a consequence of my body being symbiotic with the English-language memeplex.
Yet another set of the patterns in "me" is the set of habits I have learned in my lifetime. I consider that skills are a form of habit. Many of these may persist only so long as I live; except insofar as I happen to teach them to others. Some of the things that I habitually do, such as writing computer code to solve problems, I would also find rewarding to teach to others; and so I am likely to intentionally contribute to those patterns' persistence — for instance by teaching people how to code. Other habits, such as certain fears and anxieties, I would rather prefer not to convey to others.
There are economic patterns, which are closely modeled by certain mathematics; I have a job, buy things, donate money in a way which participates in and reinforces a "capitalism" pattern. There are moral patterns, many of which are modeled by game theory. Some of these are carried on the genome (the capacity for empathy); some of them are carried on cultural replicators (the Golden Rule). I participate in and reinforce economic and moral patterns; and this in turn makes them more prevalent and persistent in the world. (A species of sociopaths could still study the mathematics of game theory, but would not implement Hofstadter's superrationality as much as humans do.)
There are patterns in common between humans and many other evolved organisms, such as sexual dimorphism; there are social patterns that depend on those, such as sex and gender roles. Certain facts about "me" are created by these patterns.
Saying that there is another copy of "me" somewhere in the world, in this vocabulary, means saying that there are two individuals at the same point in the configuration-space of the above sorts of patterns. This seems unlikely, since there are really quite a lot of patterns that I participate in. However, we may consider how close two points in configuration-space may be to consider them "almost the same" ...
This post is not about many worlds. It is somewhat disjointed, but builds to a single point.
If an AI was asked today how many human individuals populate this planet, it may not return a number the several-billions range. In fact I’d be willing to bet it’d return a number in the tens of thousands, with the caveat that the individuals vary wildly in measure.
I agree with Robin Hanson that if two instances of me exist, and one is terminated, I didn’t die, I simply got smaller.
In 1995 Robert Sapolsky wrote in Ego Boundaries “My students usually come with ego boundaries like exoskeletons. […] They want their rituals newly minted and shared horizontally within their age group, not vertically over time,” whereas in older societies “needs transcend individual rights to a bounded ego, and people in traditional communities are named and raised as successive incarnations. In such societies, Abraham always lives 900 years--he simply finds a new body to inhabit now and then. ”
Ego boundaries may be more rigid now, but that doesn’t make people more unique. If anything, people have become more like each other. Memes are powerful shapers of mental agents, and as technology allows memes to breed and compete more freely the most viral ones spread through the species.
Acausal trade allows for amazing efficiencies, not merely on a personal level but also via nationalism and religion. People executing strong acausal trading routines will out-compete those who don’t.
Timeless Decision Theory proscribes making decisions as if choosing the outcome for all actors sufficiently like yourself across all worlds. As competition narrows the field of memeplexes to a handful of powerful and virulent ubermemes, and those memeplexes influence the structure and strength of individual’s mental agents in similar ways, people become more like each other. In so doing they are choosing *as if* a single entity more and more effectively. To an outside observer, there may be very little to differentiate two such humans from each other.
Therefore it may be wrong to think of oneself as a singular person. I am not just me – I am also effectively everyone who is sufficiently like me. It’s been argued that there are only seven stories, and every story can be thought of as an elaboration of one of these. It seems likely there are only a few thousand differentiable people, and everyone is simply one of these with some flare.
If we think of people in these terms, certain behaviors make more sense. Home-schooling is looked down on because institutional schools are about making other people into us. Suicide is considered more sinful than killing outsiders because suicide *always* reduces the size of the Meta-Person that the suicidee belonged to. Argument and rhetoric isn’t just a complete waste of your free time, it’s also an attempt to make Meta-Me larger, and Meta-SomeoneElse smaller. Art finally makes sense.
Added Bonus: You no longer have to have many children to exist. You can instead work on enlarging your Meta-Self’s measure.