Here's a fun little article that looks at the evolutionary purpose of literature. The authors believe that the function of novels is to promote pro-social virtues that will increase cooperation. The study had participants judge characters from classic novels. The characters interested only in social dominance were rated negatively, while the more group-minded characters were rated higher.
The authors mention how this may represent the values of egalitarian hunter-gatherer societies. They believe that storytelling then and now serves an evolutionary purpose of group cohesion and group quality of life. Modern democracy also could be a carryover of these ancient group values.
I'm guessing there is an evolutionary purpose to non-fiction writing as well, such as this blog. Sharing valuable information and experiences can help others. Personally, I know I have greatly benefited from the comments and discussions here. The tribe gets better when everyone contributes in a positive way.
