The Drake Equation needs a little tweaking
With trillion of stars, many with planets, where is everyone?
Calculations show that there are some 40 billion Earth sized planets in habitable zones, yet intelligent life seems to be sparse in our Milky Way.
The Drake Equation needs to add a factor for a Luna sized moon in the orbital path of the planet.
Mix it up
Why is a Luna-like rock necessary?
If the elements of life are common, what turns sludge into a multitude of species?
Mixing is the key!
Place some algae into a couple of Erlenmeyer flasks in a warm sunny place, one shaken to gently agitate the mixture. Mix long enough (e.g. eons) and watch the algae mutate into other organisms!
The static flask will be covered with dead cells and turn anaerobic and very stinky over a short period of time.
Mix it up on the Planet
Extrapolate this to a planet. Our Luna, made by the Theia collision, generates tides to mix things up. Add UV, lightning, vulcanism, and maybe a few asteroids, and life will slowly change from sludge to multi-cellular organisms. Once that point is attained, nothing can stop angiosperms, dinosaurs, and the furry and feathered from evolving.
Again, where is everyone else?
For the 40 Billion, how many stars have:
(1) Worlds orbiting in the liquid water zone
(2) Which have been hit with a Mars-sized planet
(3) AND spit off a 1000km wide piece of rock that stays in orbit?
Damn few I would say, but if you want to find intelligent life around a star, look for their large rocky moon.
Of course, there are probably other ways to generate evolving life beside a tidal moon, but so far, nothing else has been found that will do it.