Learning from Biology, Not Physics

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In the 20th century, a lot of the challenges that engineers, planners, and other city-building professionals faced seemed simple and straightforward. They were almost one-dimensional in nature, or they could at least be credibly reduced to one dimension.

Consider traffic congestion. If a street has too much traffic and drivers routinely experience significant delay and unpredictable travel times, the one-dimensional answer was to build more capacity. In the decades immediately after World War II, there was not only the budget for this kind of response, but the systems of governance also gave engineers wide latitude to execute their plans without interference from a public that may might not fully agree. If building more capacity meant tearing down half the businesses along Main Street or taking out a neighborhood’s sidewalks, trees, and crossings, then that was the price paid for what was perceived as progress.

Large budgets and unchecked authority provide the luxury of being able to see a problem like traffic congestion, or even transportation in general, as one-dimensional. It allows the professional to approach the practice of engineering as if it were a mathematical equation to be worked out, one with a single, definite answer. This is an approach similar to Newtonian physics, where equations are used to derive insights that can then be verified through simple experimentation.

In general, engineers feel most comfortable working in cities when they can treat them like a physics problem. Professional engineers are unparalleled in their capacity to solve problems that are presented to them in this way. They have manuals, charts, codes, and other guides to help them apply best practices. They confidently project what traffic will be in 20 years based on their measurements of traffic over prior decades. They know what will happen when that new housing subdivision goes in, or a new traffic signal is installed, because they have equations that (they believe) tell them exactly what will happen.

This was all fine when society could ignore the problems that arose in the wake of bad engineering practices; when we had abundant resources to throw at every complication that arose, or at least the ones we cared about. That street expansion to cure congestion may have destroyed the downtown business community, but we can tell ourselves that there are now jobs to be had at the big box store on the edge of town. We can provide aggrieved citizens some tax rebates and tuition subsidies to adapt to the new reality, which also now includes the low, low prices that our economic models suggest are optimal.

As we continue to fight congestion in one dimension, we develop more and more narratives to explain away the problems that were building up. Suggestions that Americans are spoiled, politicians are cheap, and engineers are underappreciated are all narrative coping mechanisms for professionals conditioned to work in only one dimension.

Over time, the ignored or discounted problems become increasingly difficult to suppress, especially as our resources simultaneously become stretched. Ultimately, the urgent problems we face in our cities, such as congestion but also many more, stop presenting as something akin to physics but instead act more like biology, where many complex variables interact to create an emergent and largely unpredictable order. In biological systems, there are no simple solutions, or even simple explanations, only complex feedback loops that drive adaptation or failure.

Of course, cities have always been complex, adaptive systems. In Strong Towns: A Bottom-Up Revolution to Rebuild American Prosperity, I called cities “human habitat” and noted that:

Such systems are experienced as emergent. Their order is not imposed; it just appears, as if by magic. Each interaction may be understandable on its own, but the complexity of interactions makes the entire system unpredictable. Everyone learns from experience, adapts their individual behavior and, in doing so, continuously impacts everyone else.

We often think of evolution as a process that happens incrementally over time. That’s close, but the full reality is more like how Hemingway described bankruptcy: gradually, then all at once. Traumatic events, large and small, force both adaptation and failure. The combination creates the learned wisdom that is passed on to subsequent generations.

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