Hanson’s Grabby Aliens Model is one way to explain the apparent lack of other intelligent life in the universe. Essentially, if you believe it’s possible for extraterrestrial civilizations to expand across the galaxy and transform large amounts of matter, then most observers (e.g. people) have to arrive earlier than these civilizations; since we wouldn’t exist if the extraterrestrials got here first. But others can explain it better than me, instead, I want to focus on the implications of the model assuming it’s true.
Hanson has previously claimed that the lack of alien civilizations suggests that it is typical for life to go extinct through an unknown process called the Great Filter. The Great Filter is pretty worrying, because it suggests there might be some unknown x-risk which is hard to avoid.
But the grabby aliens model offers an alternative. If we don’t see other civilizations because of selection effects, then we don’t have to worry as much about the great filter, and this reduces our expected probability of an existential catastrophe .
Grabby aliens also changes the value of existential risk reduction. On one hand, the upper bound on the size of our civilization is much smaller under grabby aliens since we must share the universe with many different civilizations. On the other hand, even if we went extinct, the universe wouldn’t remain empty since some other civilization would be there to take our place.
The presence of competing civilizations changes how we should prepare for the future. The universe fills up much faster if there are many many civilizations growing in parallel . Moving quickly can allow humanity to gather a larger fraction of the universe for itself. Additionally, it is critical to develop tools for collaboration and resource sharing between alien species.
The possibility of meeting alien civilizations also means that we have to consider how our actions will effect our reputation . Radio broadcasts have been leaving earth for a century. What do they say about us?
Being able to establish a reputation before meeting another civilization is crucial. The time period before we become aware of other civilizations gives us an opportunity to pre-commit to certain courses of action. For example, we might pre-commit to being friendly to cooperative aliens. Other civilizations may make similar commitments; but what is the equilibrium of this game?
If accurate, the grabby aliens model changes our understanding of life, existential risk, and the future of civilization. The implications just beginning to be explored and I am excited to see what people come up with next.
This also raises the profile of ideas like the Genesis project. If life is more viable than we thought, it might be worthwhile to spread it to places we will never reach (or to plant allies in places we will eventually reach).
Reputational concerns are relevant for any long-lived agent originating from our civilization.