Too hot. Too cold. Or juuuuust right? Young planets aren’t so comfy for young life forms. But hey, there’s the Earth. So, score one for biology…. Turns out young planets go through all kinds of spasms and hiccups on their way to stability. So, even if say bacterial level life manages to get itself established, things can go seriously sideways at any point after that. On Earth, bacteria ruled as sole monarchs of the place for two billion years, and only then managed to gear up into complex cells and then animal-caliber creatures. So, while we may find delightful slimey bio-film-inhabited planets aplenty, it may be hard to locate anyone able to play chess with, etc. More from the pessimists here.