Twenty years ago this month, Dolly the sheep started her life in a laboratory. She quickly gained farm animal fame as the first successfully cloned mammal. Despite her stardom, Dolly’s life was cut short by an unusually early case of osteoarthritis. Some observers thought she aged too quickly. At just six-and-a-half years old, veterinarians put her down. And with her went a lot of optimism about cloning’s potential.

Still, many hopeful scientists hypothesized that her test-tube origins had nothing to do with her tragic fate. And it turns out they were probably right.

Kevin Sinclair, a developmental biologist at the University of Nottingham in England, joined his colleagues in putting 13 other cloned sheep, some in their golden years, through a battery of tests. He and his fellow researchers found that the cloned sheep are not only healthy, but they’re aging completely normally. Four of those sheep were cloned from the exact same batch of cells as Dolly.

The study, published Tuesday in Nature Communications, cleanly counters the concern of early aging from cloning, which generally involves transferring DNA from an adult sheep cell into an egg cleared of its own DNA. To describe Dolly’s early demise, Sinclair told NPR it was “really just bad luck.”

The four Dolly relatives (Daisy, Diana, Debbie, and Denise) have just turned nine years old, which is the sheep equivalent of a human turning about 70. Along with the other nine sheep, they were put through tests involving blood pressure and diabetes risk, as well as heart, muscle, and joint functions. All of the tests came back normal, with the minor exception of Debbie. She has a little arthritis, which is normal for her age. She now takes a little ibuprofen with her breakfast.

“[The study results] really change the perception of how people look at cloning,” Charles Long, a scientist who studies artificial reproduction at Texas A&M University, told The New York Times.