Failing The Heinlein Test

I've been trying, unsuccessfully, to find the exact chapters or book passages from Robert Heinlein's writings where I first came across the concept of The Heinlein Test. He didn't call it that. It's how I thought about his ideas.

Heinlein envisioned a universe that is pretty much the opposite of the "Where IS Everybody?" Fermi Paradox. In Robert Heinlein's universe, solar systems and galaxies are teeming with intelligent life forms that evolve to develop spaceflight and move on from there. He also theorized that in such a universe, the likelihood of evolving into a multi-planetary species could be predicted by how soon an intelligent species utilizes spaceflight to the fullest extent possible, after developing the capability. A species that embraces and relishes this evolutionary milestone would flourish. Those species approaching it with temerity, risk aversion, trepidation and disinterest would perish. The longer this hesitation goes on after developing the capability for creating a multi-planetary species without actually using it, the more likely the species is to become extinct in the long term.

This may well be bullshit, but it has a certain intuitive symmetry to it. A species that embraces multi-planetary life to the fullest extent possible has an excellent long-term survival outlook. Species that hesitate years before taking this step don't have such a rosy prognosis. It starts to look pretty grim for species that take a decade, or decades to get their asses to Mars, to quote Buzz Aldrin. It's not a new idea. Entire sci-fi universes have plot lines based on multiple species with more or less aggressive expansion and colonization tactics. The more hesitant and non-spacefaring species don't do too well in this scenario, in the long run.

If there is even a smidgen of truth to this idea, it's worth noting that homo sapiens is failing the Heinlein Test, badly.

"Yeah, it got us, too." - The Dinosaurs