The plot would be for an adult audience.
Meaningful dialogue ought to be encouraged.
The story will involve various creatures and so an environmental, ecological or one that touches a persons thought processes would be ideal.
Wendy and Karin are both interested in these fields and Wendy suggested we look into Evolution of Moral Progress, which she had been researching.
Read here for some of his thoughts - though I am sure he would want to edit now that times have changed big time in the USA
Check out his The Better Angels of Our Nature
Of course some disagree with Pinker's writings but Peter Singer (a moral philosopher) is also a supporter of Pinker's work. In his book The Most Good You Can Do, Singer describes altruism as “an emerging movement” with the potential to fundamentally alter the way humans live.
He has said "we should give equal consideration to all "beings who have interests."
Check out also http://press.princeton.edu/titles/9434.html and watch the video for a pretty clear explanation.