Some scientists and ethical leaders contend the cloning of a dog carried out by Seoul National University professor Hwang Woo-suk may pave the way for reproductive human cloning. University of Ulsan professor Koo Young-mo heads critics against Hwang's stem cell research on the grounds that the science may not end until the creation of a human clone has been realized. "There were three obstacles in mammal cloning -- a dog, monkey and human. Now Hwang has surmounted the dog, taking the next step toward creating a human clone," Koo said. The evaluation is outright contrary to Hwang's continued denial of the possibility of replicating a human. Instead, he has articulated his commitment to therapeutic research on stem cells. University of Pittsburgh professor Gerald Schatten, who joined the research team as one of Hwang's closest colleagues, also flatly downplayed the likelihood of applying the technologies to create a human baby. "The brilliant work reported here demonstrates yet again that reproductive cloning is inefficient and unsafe. So we call on the world to ban human reproductive cloning, which is also unethical," he said. Even though it is a great achievement, Hwang's dog cloning remains inefficient with the study showing a dismal 0.09 percent success rate, as the team obtained only one successful clone from 1,095 eggs and embryos. However, Park Se-pill, head of Seoulbased Maria Biotech, claims human cloning would be much easier than that of a dog. "In fact, I think cloning humans might be more straightforward than cloning dogs since scientists know much more about the reproductive system of the former, rather than the latter. In addition, it is easier to obtain human eggs than those of a dog," Park contended. Park harvested human stem cells from frozen embryos, which are supposed to be discarded after artificial insemination succeeds, for the third time in history in 2000. Park said that from what he understands, Hwang denies the possibility of human reproductive cloning because he wants to focus instead on continuing his therapeutic cloning research without arousing ethical debates, rather than that his team really lacks the proper technologies to replicate a human. Indeed, Hwang's team has a knack for cloning mammals. In 1993, he caused a stir by creating Korea's first cow using in vitro fertilization and six years later he cloned a pair of cows for the first time in Korea and for the fifth time in the world. His team replicated a pig in 2002 and in Dec. 2003 they surprised global scientists by unveiling four calves that Hwang claims to be resistant to mad cow disease. The team, composed of 100-plus top researchers, has also created dozens of pigs embedded with human immunity genes that supposedly prevent negative immune responses when the pig organs are transplanted into humans, since last year.