The question isn't how many simulated observers exist in total (although that's also unknown), but how many of them are like you in some relevant sense, i.e. what to consider "typical". Many people do think they would have other reasons to run ancestor simulations. But in any case, I don't think your original idea works. Running a simulation of your ancestors causes your simulated ancestors to be wrong about the DA, but it doesn't cause yourself to be wrong about it. Trying to steelman, what you'd need is to run simulations of people successfully launching a friendly self-modifying AI. Suppose out of every N civs that run an AI, on average one succeeds and all the others go extinct. If each of them precommits to simulating N civs, and the simulations are arranged so that in a simulation running an AI always works, so in the end there are still N civs that successfully ran an AI. This implies a certain measure on future outcomes: it's counting "distinct" existences while ignoring the actual measure of future probability. This is structurally similar to quantum suicide or quantum roulette.

What did you mean by" they direct the AI to create billions of simulated humanities in the hope that this will serve as a Schelling point to them"

It's not about the number of humans. It's about the number of observer-moments. Imagine if you were the only human ever. If you're only twenty years old, it's unlikely that you'd live to be a billion. You're not going to just happen to be in one of the first twenty years.

You say that one can change A by changing B, while there is no causal mechanism by which B can influence A. That's denying causality. Well, if you don't like the term 'denying causality', feel free to replace it, but the point holds anyway. In my prior probabilities system, finding a way around causality is somewhere near finding a way around energy conservation law. No way, unless there are tons of evidence.

Ah - I'd seen the link, but the widget just spun. I'll go look at the PDF. The below is before I have read it - it could be amusing and humility inducing if I read it and it makes me change my mind on the below (and I will surely report back if that happens). As for the SSA being wrong on the face of it - the DA wiki page says "The doomsday argument relies on the self-sampling assumption (SSA), which says that an observer should reason as if they were randomly selected from the set of observers that actually exist." Assuming this is true (I do not know enough to judge yet), then if the SSA is false, then the DA argument is unsupported. So - lets look at SSA. In a nutshell, it revolves around how unlikely it is that you were born in the first small% of history - and ergo, doomsday must be around the corner. I can think of 2 very strong arguments for the SSA being untrue. First - this isn't actually how probability works. Take a fair coin and decide to flip it. The probability of heads and tails are the same, 1/2 - 50% for each. Flip the coin, and note the result. The probability is now unity - there is no magic way to get that 50/50 back. That coin toss result is now and forever more heads (or tails). You cannot look at a given result, and work backwards about how improbable it was, then use that - because it is no longer improbable, it's history. Probability does not actually work backwards in time, although it is convenient in some cases to pretend it does. Another example - what is the probability that I was born at the exact second, minute, hour, and day, at the exact location I was born at, out of the countless other places and times that humanity has existed that I could have been born in/at? The answer, of course - unity. And nil at all other places and times, because it has already happened - the wave form, if you will, has collapsed, Elvis has left the building. So - what is the probability you were born so freakishly close to the 5 million year reign