This is the beginning of Earth, before Na'pi went on their quest to beautify it. It was sort of like a blank slate.
While he walks upon the Earth, he decides to create new life for the planet. He journeys across the Earth, adding land and creatures as he goes along.
A woman with her child, created by Na'pi, is decided that she and her race will be the ones to rule the Earth freely. The woman speaks to Na'pi about mortality, and it is eventually decided that humans will be mortal, so that they can mourn for one another.