Space

Because they're jerks.

So their whole argument is that tectonic plates are needed for complex life to emerge. There isn't much proof for it either way obviously but I find the argument flawed.

In any case, here is why I think aliens are here, either waiting for us to divest ourselves of our economic system and destructive ways (capitalism breaks when you mix in easy space exploration and heavy automation) or observing us and how changes emerge in our society like we do with secluded tribes.

1. Any advanced civ can tell a planet has life on it from a great distance. If simple life is rare, they would of had a probe here a long long time ago.

2. We started modifying the climate over 3000 years ago. Any civ within an 1000 light year range would have had enough time to notice and make it here. That is around 7 million star systems.

3. An advanced civ would have covered every single solar system with Von Newman probes.

I think the fernie paradox is more of a test than a rule. Any civ that can't pull itself out of the muck is probably bad news for galactic society, so they wait and see.

The argument David Kipling made seems reasonable. Statistically the chance if there being almost no civilisations or the universe just teeming with life are the biggest. The parameters have to be tweaked just right for there being just a few civilizations in a galaxy. It's not teeming with signals and chances of parameters being just right is low, so most probable is we being alone.