This gradual process of evolution means one must come to the platform of understanding Brahman.
Advancement of civilization means brahma-darśanam. That is advancement. Because so long we do not come to the platform of understanding that "I am spirit soul, I am part and parcel of the Supreme Spirit," we are in the ignorance—in different forms. The example is given very nicely. Just like raw wood, just from the trees, you cut the trees, it is raw, it is not immediately fit for burning. But when it is little dried you can ignite fire, and, igniting fire, immediately there is no flame, there is smoke. Then, after the smoke, there is flame. And that flame is required.
So this gradual process of evolution means one must come to the platform of understanding Brahman. Ahaṁ brahmāsmi: "I am..., I am spirit soul, and I am part and parcel of the Supreme Soul." This understanding one must come. So for that understanding one has to come to the platform of goodness, sattva-guṇa. If one remains in the rajo-guṇa and tamo-guṇa, as we have explained, then we shall be entangled in this material world.