I would only bet at 30% on meeting grabby aliens

The grabby aliens argument

According to standard models of cosmology, there will be habitable planets in our universe for a very long time, and some of these planets will be much longer-lived than our Earth. If we expect the emergence of intelligent life to require multiple unlikely hard steps to accidentally happen in a row (as is a common model, usually assuming between 3 and 10 hard steps), then it should be very surprising that we find ourselves on a relatively short-lived planet early in the history of the universe. There are planets that are likely habitable for hundreds of billions of years - the chance that 3 to 10 unlikely steps happen in their long lifetime is overwhelmingly more likely than that it happens in the short lifespan of our Earth. [1] Hanson’s Grabby Aliens paper does some modeling, and almost all their models show that we should be among the first 0.1% of intelligent species to emerge.

So what explains being so early? Hanson’s answer is that some grabby alien civilizations start spreading through the galaxies with near-lightspeed, and conquer everyone in their way. Therefore, there will be no unconquered land left hundreds of billions of years from now, so intelligent life can’t develop on the long-lived planets, so Earth is actually a typical example of a cradle of civilization - you need to develop early, before the grabby aliens arrive at your planet.

Hanson also uses this as an argument that aliens likely exist - maybe you previously thought that life is rare enough that we are alone in the universe. But then it would be a huge mystery why we are not living on a long-lived planet in the far-future. The best explanation for our earliness is the existence of grabby aliens, so aliens very likely exist.

I think this is not a bad argument, but I have two objections, which make me think that I should only bet at around 30% that we will ever encounter another powerful alien civilization in the observable universe.

We are not that early if w…