Twenty years ago today, scientists at Edinburgh’s Roslin Institute introduced the most famous sheep in history. The Finn Dorset born seven months earlier was the first mammal cloned from the cells of an adult. She was named for the famously-endowed singer Dolly Parton—a nod to the mammary gland cell from which she was cloned.
Dolly’s birth made global headlines, many of which suggested that the animal blithely munching grass in Scotland was the harbinger of a dystopian future upending human reproduction. Predictions included evil clone armies, sacrificial humans created to supply organs, and dead people “resurrected” in petri dishes.
That future never came to pass. One reason is ethical: Even as we near figuring out how to clone a human, we are no closer to agreeing on when or whether we should. The other is that with few exceptions—mice and rats copied en masse for lab studies, reproducing quality livestock—cloning animals really isn’t all that useful.
Dolly’s real legacy is the research she inspired in nuclear reprogrammed cells, which will save more lives than cloned organ donors ever could. Japanese stem cell biologist Shinya Yamanaka was among those inspired by Dolly’s birth. With living, woolly evidence that it was possible to change one cell’s gene expression by swapping its nucleus for another, Yamanaka adapted the process to engineer adult human cells into stem cells, which can mature into many different cell types.
The cells created through Yamanaka’s technique, known as induced pluripotent stem cells (iPSCs), allow scientists to pursue the life-giving possibilities of stem cell research without relying on tightly-controlled, ethically-charged human embryonic stem cells. Most stem cell research today is done with iPSCs. Researchers building on Yamanaka’s techniques are now reprogramming cells to reverse the effects of age and disease.
In 2012 Yamanaka shared the Nobel Prize with John Gurdon of Cambridge University, who 50 years earlier cloned the first animal embryo using the cells of a mature adult. By determining that a frog’s egg contained the same DNA as a mature tadpole, Gurdon showed it was possible to essentially turn back the clock on a cell’s development.
Dolly, Gurdon told Quartz, “was a very important step in the great current interest in the reprogramming of adult cells to provide embryonic cells from which many other unrelated adult cells can be obtained.”
As for Dolly, she lived out her days at the Roslin Institute, giving birth to six healthy lambs (Bonnie, Sally, Rosie, Lucy, Darcy, and Cotton, in case you’re wondering) before a CT scan found tumors in her lungs. She was euthanized Feb. 14, 2003 at the age of six, and is on permanent display at the National Museum of Scotland.