It would be accurate to say that a number of scientists understand the process required to clone humans, but very few would be anxious to perform full-scale experiments to perfect that process. There are far more negative results than positive during current animal cloning procedures, with some experts suggesting only 1 or 2 successes for every 100 attempts. If scientists attempted to clone humans based on current success rates, their laboratories would most likely be shut down and the researchers could be tried for crimes against humanity. It could be decades before the technology of cloning improves enough for scientists to even consider a feasible way to clone humans.
Most cloning performed today is not of the reproductive or replicant variety, such as the case of the cloned sheep named Dolly. That procedure requires the complete removal of a donor egg's nucleus and the implantation of DNA and other materials from the animal to be cloned. This would also be the method scientists would use to clone humans, if such a process were deemed ethical. Most cloning processes in use today only splice slivers of genetic coding into cells prepared to receive it. When that cell divides, the cloned genetic information is reproduced over and over again.
There are still a number of serious ethical, moral and technical issues to be worked out before any reputable scientist could be permitted to clone humans in the same sense as cloned sheep or endangered species. The reproductive form of cloning, for example, has an unacceptably high failure rate in its current state of development. Even if a human egg cell survived the initial stripping process and accepted the foreign DNA, the embryo would still be in danger of developing serious genetic deformities or a compromised immune system. Many cloned animals today have shortened lifespans and a number of serious health problems. Before any scientist could clone humans, he or she would have to assume responsibility for any negative outcomes caused by the procedure.
Before scientists could clone humans for reproductive or replicant purposes, there would also be a question of motivation. A cloned human would not necessarily be an identical genetic twin of the donor, although they might share many of the same physical characteristics. Scientists working in medical fields such as reproduction or genetic medical research could not simply clone humans in order to replace a deceased child or create a suitable donor for a child suffering from a genetic disorder or condition. To clone humans for such self-serving or emotional reasons would be viewed as highly unethical.
Perhaps one day the technology necessary to clone humans will be perfected to the point where cloning on demand might be feasible. There will still be serious ethical and moral issues facing scientists who explore that territory, however, so human cloning may remain another instance in which the science behind a new technology far outpaces the moral, ethical and professional issues it ultimately creates.