Reaching the age of 100 was once viewed as something almost mythical, a milestone achieved by only a handful of people whose lives seemed touched by extraordinary luck, rare genetics, or divine favor. In earlier centuries, surviving childhood alone was a challenge, and infectious diseases, poor nutrition, and limited medical knowledge meant that few people lived far beyond their sixties. In the modern era, however, the idea of living to 100 has slowly shifted from legend to possibility. Advances in sanitation, vaccines, antibiotics, medical technology, and public health infrastructure have dramatically increased average life expectancy across much of the world.

As a result, more people are now living into their eighties, nineties, and even beyond. Yet despite these gains, becoming a centenarian remains far from common, and the question of why some individuals reach such remarkable ages while others do not continues to fascinate scientists, doctors, and the public alike. Among the many factors examined—diet, exercise, stress, education, income, environment, and access to healthcare—one surprisingly simple and unchangeable trait has drawn renewed interest: blood type.