Forget Rome. They had lead in their pipes, their wine, their cosmetics, and they fell, and the lead was part of what unraveled them, though not the only part. What we did was the same experiment run at industrial scale, with combustion engines, with a global economy amplifying every output, with seventy years of tetraethyl lead burned into the air over every city on the continent. We live in the distant past right now. The chapter we are inside of is one that has not finished writing the consequences we are already accumulating.
The chart on this page shows two of those consequences on the same timeline. One wave already crested. The other is still rising. Both trace to the same cohort of people, the same childhood windows, the same chemical. One damaged the heart. The other is working on the brain. The latency between them is roughly the distance between middle age and old age, which is exactly how far apart they land on the timeline.
I did not arrive at this by reading a paper that surprised me. I arrived at it by building a business selling lead detection tools and watching, year after year, who showed up to buy them and why. The people who needed the tool most had almost always already absorbed the cost. The chart is a picture of that cost, extended across an entire generation, plotted against time.