Ancestor Sims
Ancestor Simulations are the most well-known and widely discussed type of simulation hypothesis. They propose that advanced future civilizations might run detailed simulations of their own past — including people just like us.
Imagine future humans (or post-humans) who have immense computing power. Instead of reading history books, they create full virtual worlds that replay their ancestors’ lives in incredible detail — complete with conscious beings who experience the simulation as reality.
The Core Idea
This concept was popularized by philosopher Nick Bostrom in his 2003 paper “Are You Living in a Computer Simulation?” Bostrom argued that if advanced civilizations can create highly realistic “ancestor simulations,” and if they choose to run many of them, then the number of simulated people would vastly outnumber those living in the original “base” reality.
His famous trilemma boils down to this: either (1) almost all civilizations go extinct before reaching simulation capability, (2) advanced civilizations rarely run ancestor simulations, or (3) we are almost certainly living in one.
How It Would Work
In an ancestor simulation, every detail of our world — physics, biology, history, and individual experiences — would be computationally generated. The simulators could fast-forward boring parts, zoom in on interesting moments, or even run multiple versions of history to study “what if” scenarios.
The simulated people inside would have no way of knowing they’re in a simulation unless the creators left deliberate clues or glitches. From our perspective, everything would feel completely real: the taste of food, the warmth of sunlight, the joy of discovery.
Why It Matters
Ancestor simulations raise fascinating questions about probability. If future civilizations run thousands or millions of such simulations, then statistically, you are far more likely to be a simulated ancestor than a “real” one living in the original timeline.
This idea doesn’t prove we’re in a simulation, but it shifts the odds in surprising ways once you accept that advanced technology could make such detailed worlds possible.
What Makes It Exciting
Ancestor Sims connect directly to our own rapid progress in video games, virtual reality, and artificial intelligence. The better our own simulations become, the more plausible Bostrom’s idea feels. It also invites us to wonder what kind of ancestors we might become — and whether we would run simulations of our own past.
Understanding ancestor simulations lays the foundation for exploring other theory types, such as nested simulations and consciousness-based models.
Want to dive deeper?
- Nick Bostrom’s original paper (2003): Are You Living in a Computer Simulation?
- Clear video explanation: Search “Bostrom simulation argument” on YouTube