Comparing the birth and death dates of more than 86 million people over the last several hundred years has turned up a smaller than expected role for inheritance.

So much for centenarians: People have searched for years for the genetic fountain of youth, and they have largely come up empty. The new work, published today in Science, goes some way toward explaining why: it found only that 16 percent of the variation in how long people live is due to genes. Previous estimates were around 25 percent.

So, no genetic test for life span? Some people have worried that insurers could use genetic tests to predict when you’ll die. “We show the value is pretty minute,” says Yaniv Erlich, chief scientist of genealogy company MyHeritage, who led the project.

Other fun facts: The study also found that over time we’ve married people less closely related to us. Migrations (like the colonization of the Americas) and new means of travel (railroads) help explain why we’ve become less likely to marry a distant cousin, but cultural factors have also played a role.