This article from +Kevin Kelly presumes that all planets with sentient beings would have the same variables that inform those thresholds. Given that we only have one planet with sentient beings as a sample there is little data to support or contradict the point. But should we just presume that all planets that are fortunate to sustain life will see that life develop along the same vector? His book makes the argument that the physical rules of the universe create a scaffold or form upon which technological progress shapes itself. That form is then transferrable to other worlds where the right conditions exist to start that progress. Is elemental life the same as technological progress and sentience that is similar to us is inevitable? Given how little we know about the universe there is a good chance we might encounter sentience and not have the tools to even recognize it. This list of thresholds might be fueled by an anthropocentric assumption. We must always challenge our assumptions.
What kinds of developmental thresholds would any planet of sentient beings pass through? The creation of writing would be a huge one. The unleashing of cheap non-biological energy is another. The invention of the scientific method is a giant leap. And the fine control of energy (as in electricity) for long-distant communications is significant as well, enabling all kinds of other achievements. Our civilization has passed through all these stages; what are some future transitions we can expect — no matter the fashions and fads of the day? What are the emergent thresholds of information and energy organization that our civilization can look forward to? Most of these thresholds are gradual, so we can’t assign dates, but each of these structures seem to be a natural transition that any civilization must reach sooner or later.