The research conducted by the Anu was always meant to be done from a distance. The evolution of sentience is a very delicate process, and even the slightest interference can cause long term damage to the system.
The Anu knew this, of course. They greatly honoured the process of natural development.
They studied from above, with long-distance probes and through observation. The biomes they built on their ship allowed them to study and experiment under various conditions, without interfering with native development.