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.