Human cloning was first widely discussed in the 1970s as a result of rapid advances in genetics. However, because human cloning did not appear to be imminent, the topic quickly disappeared from public view. The appearance of Dolly, the cloned sheep, in 1997 unexpectedly made human cloning more realistic. The ethical implications of human cloning have since been revisited.
As with most emerging technologies, concerns about safety provide the most obvious ethical grounds for caution. Somatic cell nuclear transfer (SCNT), required to clone an existing person, poses a risk in passing on mutations in the source cell's DNA, which could result in unexpected anomalies. In addition, cloned offspring might also be born with a cellular age equivalent to that of the genetic progenitor and would have a reduced overall life span. As with all in vitro technologies, cloning raises concerns about physical damage to the embryo and health risks for women who undergo ovulation induction and surgical egg retrieval.
Although research may settle these worries about safety, several more abstract issues may be harder to resolve. A primary concern involves individuality. Although naturally occurring identical siblings sometimes feel that being a twin undermines their unique identities, they generally seem unharmed by having a natural clone. However, although most of us are not greatly bothered by the notion that one other identical person