The Mad planet had been seeded for life, first with microbes and later with plants and insects. A third expedition, intended to complete the seeding with animals, never occurred. Over the millennia the insects and plants grew to gigantic sizes.
The action of the novel describes the fight for survival by descendants of a crashed spaceship as they battle wolf-sized ants, flies the size of chickens, and gigantic flying wasps.
And so those few remaining humans were unknowingly at the very beginning of the building of a tribal society, which at the time of the story of Burl simply meant food and survival.
And so it was Burl who chose to travel beyond his small tribal community in an effort to hunt for something new and different to hopefully impress Saya, the young female of his tribe to whom he felt a peculiar attraction. The Mad Planet is Burl's adventure.