In this 2003 paper, Loren Cordain and colleagues examine why myopia—commonly called nearsightedness—has become so widespread in the modern world. Today roughly 40% of the U.S. population is myopic, yet studies of traditional hunter-gatherer groups show rates typically between 0–2%. The authors point to evidence from indigenous populations undergoing Westernization, where myopia rates increased dramatically within a single generation as refined grains, sugar, and other modern foods were introduced.

Cordain and colleagues propose that high consumption of refined carbohydrates may increase insulin levels, which can elevate IGF-1, a hormone involved in tissue growth. Elevated IGF-1 during childhood may promote elongation of the eyeball, the physical change that produces myopia. While near-work and literacy have often been blamed for worsening eyesight, the researchers found that literate populations maintaining traditional diets had far lower rates of myopia than urban children eating modern diets. They conclude that the rapid rise of nearsightedness may be another example of evolutionary mismatch, where modern dietary patterns disrupt biological systems that evolved under very different conditions.