Over the span of the next three days, I met some of Leriadis’s patients. In the area known as Raches, I met 20 people over 90 and one who claimed to be 104. I spoke to a 95-year-old man who still played the violin and a 98-year-old woman who ran a small hotel and played poker for money on the weekend.

On a trip the year before, I visited a slate-roofed house built into the slope at the top of a hill. I had come here after hearing of a couple who had been married for more than 75 years. Thanasis and Eirini Karimalis both came to the door, clapped their hands at the thrill of having a visitor and waved me in. They each stood maybe five feet tall. He wore a shapeless cotton shirt and a battered baseball cap, and she wore a housedress with her hair in a bun. Inside, there was a table, a medieval-looking fireplace heating a blackened pot, a nook of a closet that held one woolen suit coat, and fading black-and-white photographs of forebears on a soot-stained wall. The place was warm and cozy. “Sit down,” Eirini commanded. She hadn’t even asked my name or business but was already setting out teacups and a plate of cookies. Meanwhile, Thanasis scooted back and forth across the house with nervous energy, tidying up.

The couple were born in a nearby village, they told me. They married in their early 20s and raised five children on Thanasis’s pay as a lumberjack. Like that of almost all of Ikaria’s traditional folk, their daily routine unfolded much the way Leriadis had described it: Wake naturally, work in the garden, have a late lunch, take a nap. At sunset, they either visited neighbors or neighbors visited them. Their diet was also typical: a breakfast of goat’s milk, wine, sage tea or coffee, honey and bread. Lunch was almost always beans (lentils, garbanzos), potatoes, greens (fennel, dandelion or a spinachlike green called horta) and whatever seasonal vegetables their garden produced; dinner was bread and goat’s milk. At Christmas and Easter, they would slaughter the family pig and enjoy small portions of larded pork for the next several months.

During a tour of their property, Thanasis and Eirini introduced their pigs to me by name. Just after sunset, after we returned to their home to have some tea, another old couple walked in, carrying a glass amphora of homemade wine. The four nonagenarians cheek-kissed one another heartily and settled in around the table. They gossiped, drank wine and occasionally erupted into laughter.

Image Figures from the Ikaria Study, which surveyed the island's over-80 population

Dr. Ioanna Chinou, a professor at the University of Athens School of Pharmacy, is one of Europe’s top experts on the bioactive properties of herbs and natural products. When I consulted her about Ikarians’ longevity, she told me that many of the teas they consume are traditional Greek remedies. Wild mint fights gingivitis and gastrointestinal disorders; rosemary is used as a remedy for gout; artemisia is thought to improve blood circulation. She invited me to give her samples and later tested seven of the most commonly used herbs on Ikaria. As rich sources of polyphenols, they showed strong antioxidant properties, she reported. Most of these herbs also contained mild diuretics. Doctors often use diuretics to treat hypertension — perhaps by drinking tea nightly, Ikarians have gently lowered their blood pressure throughout their lives.

Meanwhile, my colleagues Gianni Pes and Michel Poulain set out to track down the island’s 164 residents who were over 90 as of 1999, starting in the municipality of Raches. They found that 75 nonagenarians were still alive. Then, along with additional researchers, they fanned out across the island and asked 35 elderly subjects a battery of lifestyle questions to assess physical and cognitive functioning: How much do you sleep? Did you ever smoke? They asked them to get up and down from a chair five times and recorded how long it took them to walk 13 feet. To test mental agility, the researchers had subjects recall a series of items and reproduce geometric shapes.