Dolly's sheep clones are doing just fine

Twenty years after Dolly the Sheep was born out of a test tube, four sheep cloned from her DNA are healthy and aging normally, according to a study published this week. The findings, published in the journal Nature Communications, may dispel long-held concerns that cloned animals age prematurely.

Many of those concerns arose after Dolly was cloned. The sheep appeared to age faster than normal, and suffered from osteoarthritis in her knees and hips at an early age. After she was diagnosed with an incurable lung virus, veterinarians decided to put her down, at the age of six. Widespread concerns over the health effects and ethics of cloning led to a UN ban on human cloning in 2005; several countries have also banned reproductive cloning...