Has science moved a step closer to producing human clones?
The question has been raised after scientists in China produced two genetically identical monkeys.
Zhong Zhong and Hua Hua are the first primates to be cloned using the DNA-transfer technique which produced Dolly the Sheep 20 years ago.
Populations of genetically identical monkeys are now expected to be created to help with future research into human diseases.
Campaigners however fear this is a step towards human clones and have hit out at the research.
Activists also claim the tests involve unacceptable cruelty to animals.
Dolly made history in 1997 after being cloned using somatic cell nuclear transfer, which involves transferring cell nucleus DNA to a donated egg cell that is then prompted to develop into an embryo.
Sheep, cattle, pigs, dogs, cats, mice and rats have all been cloned with this method, but this is the first time a monkey has been cloned using this technique.
The Chinese team made the breakthrough by using DNA from foetal connective tissue cells.
After the DNA was transferred to donated eggs, genetic reprogramming was used to switch on or off genes that would otherwise have suppressed embryo development.
Scientists have allegedly admitted that their work has resulted in the abnormal development and death of many monkeys.
Zhong Zhong and Hua Hua were the result of 79 nuclear transfer attempts. Two other monkeys were initially cloned from a different type of adult cell, but failed to survive.
Dr Katy Taylor, from Cruelty Free International, said: "The scientists themselves admit that their work has involved the abnormal development and death of many monkeys before and after birth.
"The scale of suffering and death of these highly intelligent and sensitive animals is substantial."
Researchers maintain that cloned monkeys would allow scientists to study "a lot of questions" about primate biology.