When Dolly the Sheep was created in a lab in 1996, the world changed. The fact that scientists successfully cloned a mammal from an adult cell, not an embryonic cell, proved that the nucleus of an adult cell has all the DNA necessary to create another animal. But a few years later, the future didn't look so bright. Dolly had issues when it came to her DNA, especially her telomeres. Telomeres are caps on the ends of chromosomes that act like a bomb fuse; the shorter they get, the less time you have left. Dolly's telomeres were shorter than other animals her age, suggesting she was aging more quickly than normal. She suffered from osteoarthritis in her knees and hips, and eventually contracted an incurable lung virus that led veterinarians to put her down at the age of six. This caused enough concern that the UN banned cloning of humans and several other countries banned reproductive cloning of animals.
But in July of 2016, scientists announced that 13 cloned sheep, including four cloned from the same DNA source as Dolly, were healthy and aging normally. Even when nearing the ripe old age of 10, the sheep showed normal blood pressure, heart function, metabolism, and joint health. This means that cloning doesn't automatically cause health problems, and that Dolly's issues may have just been a fluke. To scientists, this is nothing surprising. Reproductive biologist Mark Westhusin, who helped create the first cloned cat who was also healthy at age 15, put it this way to Science News: "This is a nice paper to confirm in a more formal scientific setting what most people involved with cloning have believed for a long time." Explore the future of cloning with the videos below.