Each culture (religion and civilization) has their own ideas about how the world began. In modern times, many of the stories have become mythology as science gives us new theories to consider. But, the old creation stories have a lot of character, detail and history.
A creation myth is a symbolic narrative of how the world began and how people first came to inhabit it. While in popular usage the term myth often refers to false or fanciful stories, formally, it does not imply falsehood. Cultures generally regard their creation myths as true.
Source: Creation myth – Wikipedia, the free encyclopedia
Decide on a culture (one you know well) and write a theory of how those people came to exist. How did the animals, plants, sky, (and everything else) begin for that culture. Don’t get stuck being too factual. Exercise both sides of your brain to merge fact and fancy. How would you like the story to go, based on some of the facts as you understand them.