The Watchman's Rattle summary

Every era has its shiny new tools, its clever systems, its sense that “this time, we’ve figured it out.” But time and time again, that confidence can prove to be misplaced. The problem is what the author calls the brain-speed gap.

To put it simply, the worlds we build change so fast that we can’t actually evolve and keep up with it. Instead, we remain stuck in our ways and big problems go unsolved. Right now we have new laws, technologies, markets, and scientific discoveries that our human brains struggle to keep track of. So, while the way the world functions may change dramatically within one or two generations, our brains only change on a much slower evolutionary timeline. That mismatch can be seen as playing a big role in the repeating historical cycle of boom, stall, and collapse.

We can see it with the great empires of the past, including the Mayans, the Romans, and the Khmer Empire. At their height, the Mayans supported enormous populations in harsh territory without any modern infrastructure. Still, they built sophisticated cities and systems that continue to astound. But then the civilization unraveled within a relatively short amount of time. 

Scholars agree that a sustained period of drought contributed to this downfall. But if we look at what happened just prior to the drought, we can also identify how shifts in the Mayan society made them less able to respond.

To make a long story short, Mayan civilization had become too intricate for the society to fully grasp. It had grown to such a point that the available mental tools, institutions, and coordination capacity proved insufficient to save the day. When you reach that point, problems don’t disappear. They stack. They get handed forward like unpaid bills. Collapse rarely arrives like a lightning strike. It shows up after a long period where progress slows, decision-making thickens, and solutions start dying in committee.

Costa flags two early warning signs. The first is gridlock: a society can name its threats – water stress, instability, environmental damage – yet can’t move decisively. 

The second is a drift toward beliefs replacing evidence. Belief itself is part of being human, and it helps people function under uncertainty. It’s bad news when evidence becomes too hard to gather and comforting narratives grab the steering wheel.

The Maya illustrate this arc. As pressures grew, practical efforts gave way to religious and ritual responses, and the unresolved issues swelled across generations. Rome shows a parallel pattern: the empire became so expensive and complex to maintain that there was no conceivable system to meet the combined needs of the economy, governance, and defense.

In these and other cases, collapse needn’t be guaranteed. As we’ll see in the sections ahead, the key is noticing the threshold early, while there’s still room to adapt. That sets up the next question: when the mind hits its limits, how can we generate the needed breakthrough?