An American doctor measured one fingernail for 35 years, his scientific experiment won an Ig Nobel but in literature

Every few weeks, most people clip their fingernails without giving them a second thought. Dr. William B. Bean did the opposite. At the beginning of every month, the American physician carefully carved a tiny groove near the base of his left thumbnail, noted the date, and waited. When the mark finally reached the tip of the nail, he recorded exactly how many days it had taken. Then he repeated the process the following month.

He kept doing it for 35 years. His unusual experiment started as a simple observation in the 1940s and gradually evolved into one of the longest self-observation studies ever documented in medicine. Through nearly 450 months of meticulous record-keeping, Bean transformed an everyday body part into a biological timeline, one capable of revealing how the human body ages, responds to illness, and changes over decades. His findings, published in Archives of Internal Medicine in 1980, showed that the average growth rate of his left thumbnail steadily slowed from 0.123 millimetres per day when he was 32 years old to 0.095 millimetres per day at age 67.

But the experiment became much more than a study of nail growth. Along the way, Bean discovered that illness could temporarily halt nail growth entirely. He observed that different fingers grew at different speeds, with the middle finger consistently outpacing the thumb and little finger, while toenails grew more slowly than fingernails. He also reviewed evidence showing that nail growth could accelerate during pregnancy, in warmer environments, and even among habitual nail-bitters, while slowing with age, reduced blood flow, and prolonged immobilization. Together, these observations suggested that nails preserve a record of the body's changing condition over time rather than simply growing at a constant rate.


Bean believed nails were more than pieces of keratin that needed trimming. In his paper, he compared them to tree rings, whale baleen, and the growth layers found in bears' teeth, structures that preserve the history of a living organism. Just as scientists can estimate the age of a tree from its rings or reconstruct parts of a whale's life from its baleen plates, Bean argued that a slowly growing fingernail could record the subtle effects of aging, disease and recovery if someone observed it patiently enough.

More than four decades after the paper appeared, Bean's unusual dedication earned unexpected recognition. The 2025 Ig Nobel Prize in Literature honored his decades-long commitment to recording the growth of a single fingernail, research that perfectly matched the awards' philosophy of celebrating studies that "make people laugh, then think." Behind the humor lay a serious scientific lesson: sometimes the most ordinary parts of the human body can reveal extraordinary stories, provided someone is willing to watch them long enough.