As a teenager in Germany, Steve Horvath dreamed of living to 1,000 years. That ambition, sparked by science fiction novels and the prospect of interstellar travel, led him to make a pact with friends to dedicate their lives to extending human longevity. Decades later, Horvath, now 58, has turned that youthful promise into a groundbreaking career in aging research.
Horvath is a geneticist best known for creating the first widely used biological-age clock in the early 2010s. The clock, based on DNA methylation—a chemical modification of DNA—allows scientists to measure the biological age of cells, tissues, and organs, providing a precise way to quantify the aging process. His invention marked a turning point in the field, offering researchers a reliable tool to study age-related diseases and interventions.
Since then, Horvath has developed multiple clocks, including a pan-mammalian clock for measuring age across different species and GrimAge, which he describes as “the world’s most accurate mortality-risk predictor.” “It’s named after the Grim Reaper,” he said. “It measures the probability that you will die in the next year.”
Horvath, formerly a professor at UCLA, is now principal investigator at Altos Labs’ U.K. research branch, a biotech firm focused on therapies that could reverse age-related decline. He says that precise measurements of aging are essential for testing longevity treatments. “It’s a quintessential tool to find interventions for rejuvenation,” he added.
His interest in aging research began with a teenage fascination for space travel and the realization that human lifespans were too short to explore the stars. Inspired by the Sumerian epic of Gilgamesh, Horvath and friends created the so-called “Gilgamesh contract,” vowing to pursue rejuvenation science. Though his friends initially diverged into other careers, Horvath’s path ultimately led him back to longevity research.
Horvath first applied DNA methylation to aging by chance while analyzing data from a twin study. The results were so striking that he knew immediately the approach could transform the study of human aging. His first chronological-age clock could predict an individual’s age within five years using saliva samples. Over time, he expanded this into clocks for blood, skin, and multiple organs, now widely used in research laboratories worldwide.
At Altos Labs, Horvath continues to use and refine epigenetic clocks, including a multi-species clock that has already been applied to studies on animals such as the axolotl, known for its regenerative abilities. The research focuses on rejuvenation strategies, including gene therapies and small molecules that could one day slow or reverse aging.
When asked if humans are closer to his teenage dream of extreme longevity, Horvath said, “We’re not close at all. It’s totally science fiction. But my mathematical answer is, I do think at some point there will be drastic extensions of lifespan. Imagine we have 100 more years of biomedical innovations—what will that do for health?”
Horvath’s work, from a teenage pact to cutting-edge epigenetic clocks, underscores both the promise and the challenges of extending healthy human life.
