 You know, I wasn't sure about this book about how civilization arose due to alcohol, but I'm really glad that I gave it a shot. After World War II, crime rates slowly but drastically increased in the United States. Theft, larceny, violent crime almost quadrupled since the 1970s, but in the 1990s that trend reversed suddenly. Across the board, in every category you might imagine, crime rates plummeted and have continued to decrease. There have been numerous explanations proposed for this abrupt reversal. Immigration, the use of crack cocaine, legalization of abortion, number of police officers, any or all of these factors may have contributed to the crime and drop in criminal activity. But one theory paints a particularly dramatic picture of the event with profound implications. Lead is a very useful element used in all sorts of industrial processes and commercial products. Batteries, ammunition, weights, that vest that you wear during X-rays to protect your bits and stained glass windows all use it in various forms. Unfortunately, it also has some nasty properties when introduced into the body, and no, I'm not just talking about getting shot. Absorbing lead via ingestion or aspiration of airborne particles can lead to all sorts of health problems. It's carcinogenic, it causes headaches. Fatigue, loss of appetite, memory loss, nausea, vomiting, high blood pressure, pain in the joints and abdomen, and eventually death. But that stuff only happens at relatively high concentrations. You'd have to be very unlucky or very foolish to be exposed to lead in quantities that would result in those sorts of symptoms. The much more insidious and dangerous problem is what lead exposure does to growing brains. Some lead ions have a charge of plus two, like calcium, one of the primary chemicals in the human nervous system. It can take the place of calcium in some of those reactions, which can affect the processes that build the brain over time. Children who absorb even minute quantities of lead can have significant physiological differences in how their brains develop, and significant behavioral changes as a result. As they grow, children exposed to lead tend to have issues with inhibition and emotional regulation, which can manifest as social aggression. They're at increased risk for attention disorders, which might be part of why they have lower IQs. There's evidence showing correlations between childhood lead exposure and a whole slew of negative life outcomes, things like substance abuse problems and poor performance at work. Obviously, there's a great deal of variance in the ultimate result, that there's a massive body of research suggesting that exposing children to trace amounts of lead can be disastrous. Prior to legislation, like the Lead-Based Poisoning Prevention Act of 1971, lead was used in many places which would subject children to its many neurological effects. Paints, furniture, and most notably leaded gasoline, which was great for engine performance and efficiency, flooded the environment with lead. We can test for lifetime lead exposure by examining bone marrow, and sure enough, people who grew up during those years where lead was prevalent, especially people from dense urban environments with lots of cars and apartment complexes with tons of lead-based paint, have a higher concentration of lead in their bones than children born a generation after the legislation went into effect. It starts to seem plausible that the decades-long trends we saw in crime might be due, at least in part, to the effect of lead exposure on children's brains. Okay, but as we've noted, all sorts of other crazy stuff was happening in the world at the same time. Why should we give a second thought to such an unconventional explanation when more traditional arguments about things like culture, economics, and politics might be just as valid? Well, leaded gasoline wasn't immediately banned everywhere all at the same time when the legislation passed. Some states and cities, after learning of its harmful effects, implemented strict local legislation immediately, while others followed a more gradual plan for slowly phasing it out. We can track crime rates in those regions and compare them, and sure enough, it seems that the faster your town got rid of lead, the faster that drop in crime occurred. Using analytical techniques like this, some researchers have argued that lead exposure is the largest part of the rise and fall of crime rates between the 70s and the 90s. By some estimates, it accounts for as much as 90% of the variance. The thought that simply adding lead to our gas may have resulted in decades of suffering, that the whole nation's average IQ was lowered by a few points, that a huge number of people who would have otherwise been responsible citizens became criminals solely because they were poisoned as babies. It's a big idea. The lead crime hypothesis certainly has critics who think that attributing such a massive social trend to such a narrow cause is misguided, but I don't think that anyone would argue that we should start letting our gas again. What's particularly fascinating to me is the idea that societal and cultural changes might be the result of introducing or removing certain chemicals from the environment. Usually, when we're thinking at that scale, we're appealing to abstract, high-level causes and influences, things like ideologies, religions, philosophies, big concepts that change the way that people think about the world and their place in it. We don't usually consider the ambient concentration of a particular element, as the determining factor in the rise and fall of civilizations. But when you start to think along those lines, you get some interesting results. Stephen Johnson, historian and author of Where Good Ideas Come From, has pointed out that the age of enlightenment, seen by many as the origin of modern scientific and rational secular thought in Europe, very closely coincided with the introduction of a few beverages to the region, coffee from the Turks and tea from India and China. Enlightenment philosophy flourished in coffee houses, with many new and interesting ideas emerging over many a 17th century cup of joe. Because they didn't yet know how to purify water, before the introduction of these new-fangled drinks, Europeans tended to consume other processed beverages, primarily beer, wine, and gin. Johnson highlights how they essentially transitioned from drinking alcohol, a depressant, to caffeine, a stimulant. Other cultures were drinking coffee and tea long before Europeans were, so it would be ridiculous to attribute the movement solely to the switch from downers to uppers. But again, there's a curious connection between the prevalence of certain chemicals in the environment and large-scale social trends. One has to wonder what other substances this framework might extend to. Nicotine, mercury, LSD, lithium, THC, sugar? We tend to think of humans as individuals with their own agency, but we also behave as mechanisms of cause and effect in the large interconnected machine of our environment. And if you restrict the flow of, say, calories or alcohol into that machine, it's not unreasonable to think that there might be reliable consequences. What do you think of the implications of the lead crime hypothesis? What substances do you imagine having large-scale social effects due to our exposure to them? Please leave a comment below and let me know what you think. Thank you very much for watching. Don't forget to bubble, subscribe, blah, share, and don't stop thunking.