The story you just read is a simplified fusion of events that must’ve happened to our ancestors countless times, but it’s more than that: It’s a parable that shows how and why our morality does not depend on religion. It illustrates how the roots, the baseline of human morality evolved before and independent of modern religious faith.
Imagine the events in The Parable of Grog and Zog repeated hundreds, thousands, millions of times down through the generations. Think about which individuals lasted long enough to reproduce, which individuals reproduced more, and which types of bands were likely to survive over time. (Hints would have to include intelligence, imagination, cooperation, nurturing, and the ability to trust “teammates” in the game of survival.)
So, contrary to common belief, it’s not just aggression, gluttony, selfishness, and xenophobia that come from nature. The good stuff has been bred into us too. Nature has long been blamed for the Hobbesian “nasty, brutish, and short” aspects of human existence, but it's only recently getting credit for the other traits that make us human, not to mention humane.
Even if most of us aren’t wearing loincloths or carrying spears, The Parable of Grog and Zog is vital: Stories have power (see Bible, etc), and understanding that morality has natural roots would undercut one of the world's most widespread prejudices -- the parochial and ill-informed assumption that the non-religious must be non-moral. Knowing that morality has natural roots would also counteract the twisted, institution-serving, and self-fulfilling notion that a newborn baby is a somehow a “sinner.” (In reality, growing body of research shows that humans and other mammals are born with an urge to help others, whether those others are blood relatives or not.) But maybe most importantly, understanding that morality has natural roots would chip away at one of humanity’s most persistent sources of division. Imagine if the vast majority of people -- religious and otherwise -- understood that the baseline (not the particulars, but the baseline) of morality was something shared throughout humanity. That's not an "anti-religion" idea; it's a UNIFYING, pro-human concept regardless of faith or lack thereof.
Our Big Ethical Question isn’t “Which faith must ‘win out’ for us to live in peace?” but, “Which human traits are still desirable, and which are counterproductive today?” Believe it or not, I think most people would agree on the answers, once we ask the right question.
So, my brothers and sisters, go forth and spread the gospel of Grog and Zog. Given a wide audience and time, this reality-based story could help us all.