Far from being an exotic, hard-to-believe explanation for the rise and fall of violent crime, the truth is that lead is actually an explanation that makes perfect sense. After all, we have multiple prospective studies that associate lead with arrest rates for violent crime in individuals. We have MRI studies showing that lead affects the brain in ways likely to increase aggression levels. We have copious historical evidence of the effect of high doses of lead on workers: for years people said it made them “dumb and mean.” We have medical studies showing that prisoners convicted of violent crimes have higher lead levels in their teeth than similar populations. We have studies linking lead exposure to juvenile delinquency. Dose-response effects litter the literature. And much, much more.
In retrospect, if I were writing my article over again I’d begin with this evidence. I chose to begin with the population studies mainly for narrative purposes, but I think that was a mistake because it led a fair number of readers, like Manzi, to believe that the Reyes paper was the linchpin of my argument. But it’s not. It’s just one confirming piece in an ocean of evidence.