Today's Wisdom - Air Conditioning, El Salvador and Zinc

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When Lee Kuan Yew was asked in a 2009 interview with New Perspectives Quarterly what had enabled Singapore's astonishing rise, his answer surprised everyone. He did not name trade, education, or his own iron discipline. He said air conditioning. He called it perhaps one of the signal inventions of history, arguing that it changed the nature of civilization by making development possible in the tropics. In the sweltering heat near the equator, without air conditioning you can work only in the cool early-morning hours or at dusk. One of the first things he did as prime minister was install air conditioners in the buildings where the civil service worked, calling it the key to public efficiency.

The idea sounds eccentric until you look at the long human relationship between heat and work. For most of history, hot climates organized life around avoiding the midday sun, which is exactly why the siesta evolved across Spain, Italy, and Latin America, with shops shutting and people resting through the punishing early afternoon before returning to work in the cooler evening. Heat measurably slows the brain, dulls concentration, and drains the energy that careful, sustained labor demands. Whole regions were effectively capped in productivity by their thermometers, which is one reason why so much early industrial wealth clustered in cooler temperate zones.

What makes Lee's insight powerful is the general principle hiding inside it. Any technology that lets humans control their environment, especially one that works with our biology rather than against it, hands its owners an enormous advantage over those still at the mercy of nature. Fire, indoor plumbing, and antibiotics all did this, and so did the humble air conditioner, quietly unlocking the tropics for offices, factories, and round-the-clock work. The man who built one of the richest nations on Earth believed that the machine cooling the room mattered as much as any policy he ever wrote, because a comfortable mind is a productive one.

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A decade ago, El Salvador was the most violent country on Earth outside a war zone. In 2015 it recorded 106 homicides per 100,000 people, with gangs like MS-13 and Barrio 18 ruling entire neighborhoods through extortion, fear, and casual murder. Shopkeepers paid weekly bribes to stay open, and bus drivers were killed for missing payments. Then in March 2022, after a single weekend in which gangs killed 87 people, President Nayib Bukele declared a state of exception that suspended constitutional rights and let security forces arrest anyone suspected of gang ties without a warrant. By 2025 the homicide rate had collapsed to 1.3 per 100,000, lower than the United States, and the government reported just 82 murders in the entire year.

The centerpiece of this campaign is CECOT, a mega-prison built to hold 40,000 inmates, now the largest in the world. Prisoners get no visitors, no outdoor time, and no rehabilitation. Around 90,000 people have been detained, roughly two percent of the adult population, giving El Salvador one of the highest incarceration rates anywhere. The transformation has been so visible that Honduras, Ecuador, and Argentina have studied or copied parts of the playbook, and the Trump administration paid Bukele to house deportees inside CECOT. At home, the results made Bukele perhaps the most popular leader in the hemisphere, with approval ratings above 80 percent and a 2024 re-election won with 85 percent of the vote.

The cost of this safety is where the story turns uncomfortable. Human rights groups have documented hundreds of deaths in custody, mass arrests with little evidence, and thousands of innocent people swept up, around 8,000 of whom were later released. The same Supreme Court that cleared Bukele's path to re-election had been reconstituted by his allies, and in 2025 lawmakers removed presidential term limits entirely. Critics abroad call him a dictator dismantling democracy, while Salvadorans who once lived under gang rule mostly call him the man who gave them back their streets. El Salvador has become the great test of an old question: how much freedom people will trade for the simple ability to walk home safely, and whether that bargain can hold once the gangs are gone.

Zinc rarely gets the attention lavished on vitamin C or vitamin D, yet it quietly powers an astonishing amount of human biology. The body needs only trace amounts, but those tiny quantities act as a cofactor for nearly 100 different enzymes, helping drive everything from cell growth to the creation of DNA. Crucially, the body has no way to store it, which means you must take in a small supply every single day through food. Zinc sits at the center of the immune system, where it is essential for the development and function of the cells that hunt down viruses and bacteria, including T cells, B cells, and the aptly named natural killer cells. When zinc runs low, this whole defensive network slows, which is why even a mild deficiency leaves people more prone to infection.

Its second great role is repair. Zinc is woven into every stage of wound healing, from clotting the initial bleed to building the collagen that gives new tissue its strength, which is why doctors have used it on skin for thousands of years. Ancient Greek physicians spread zinc oxide ointment on wounds, and the same compound still sits in modern sunscreen, calamine lotion, and diaper-rash cream, forming a protective barrier while reflecting the sun's harmful rays. Zinc also governs the senses of taste and smell, helps produce testosterone, and calms the inflammation behind acne and rosacea. The richest food source by far is the oyster, followed by beef, with eggs, dairy, beans, and pumpkin seeds all offering steady supplies for those who prefer not to eat shellfish.

The benefits of supplements show up mainly in people who are genuinely deficient, a group that includes many older adults, strict vegetarians, and those recovering from serious burns or surgery. For everyone already getting enough from food, swallowing extra pills delivers little and can actively backfire, because high doses block the absorption of copper and may eventually harm the nervous system. Adults should generally stay under 40 milligrams a day from all sources combined. Zinc lozenges taken at the first tickle of a cold may shorten it by a day or two, though they will not stop one starting, and zinc nasal sprays carry a rare risk of permanently destroying your sense of smell. The lesson is to get it from your plate first, and treat the supplement bottle with respect rather than enthusiasm.

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