For many people, the word “clone” conjures terrifying images of a dystopian future. We worry about the moral and philosophical implications of creating genetic copies. Cloning scientists have concerns, too, although theirs are often more technical: is cloning harmful to the organisms it creates? In the case of Dolly the sheep’s cloned offspring, at least, the answer appears to be no. Scientists say the four eight-year-old sheep are just as healthy as other sheep their age. They published their findings in the journal Nature Communications. 

The world’s first cloned animal drew her first breath in 1996. Dolly’s birth was met with elation, outrage, and fascination—reactions that would follow her throughout her life. The world was watching when the sheep was diagnosed with osteoarthritis at the relatively young age of five. She died just a year and a half later, prompting concerns that the somatic-cell nuclear transfer (SCNT) process that brought her to life had also accelerated her aging, illness, and death. 

Five years later, a new class of clones entered the world. Debbie, Denise, Dianna, and Daisy had been copied from Dolly’s DNA using the same SCNT process. Would their lives go the same way as Dolly’s? Researchers could only wait and see. 

Debbie, Denise, Dianna, and Daisy (we're not sure which is which, but can you blame us?). Image Credit: Nottingham University.

The Nottingham Dollies, as the four new clones are called, sailed through ages one through seven without a hitch. When the clone club reached their eighth birthday (which equates to about 60 to 70 in human years), scientists decided it was time for a thorough checkup. 

They brought the Dollies and nine other cloned sheep between the ages of 7 and 9 into the lab and searched for signs of aging-related ailments. Researchers tested the sheeps’ glucose tolerance and insulin sensitivity, their heart rates and blood pressure, and the health of their joints. Their results were then compared with those from a group of the university’s naturally conceived sheep. 

Cloned or no, all the sheep were in pretty robust health for their ages. The researchers could find no signs of diabetes or hypertension in any of them. A few of the sheep, including Debbie, had mild to moderate osteoarthritis, but even this was less severe than Dolly’s, and she was younger when she died.

There’s still plenty of room for improvement in the SCNT process, lead author Kevin Sinclair said in a press statement. But he’s confident the process will improve, and that we’ll be able to use it to create stem cell therapies for people and healthy transgenic animals. “However, if these biotechnologies are going to be used in future,” he said, “we need to continue to test their safety.”

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