The stock title for this topic indicates a prejudice against cloning. Strictly speaking, any plant nursery practices "cloning" when they propagate plants using shoots rather than seeds. However, the intent of this article seems to be concerned with the practice of using animal tissue (other than earth worms, who sort of do this naturally) to artificially create a living being. Dolly, the lamb, was the earliest example of this type of cloning.
Dolly was created by inserting an adult cell from the parent sheep's udder into a sheep's egg. The egg was then implanted in a surrogate mother. The Scottish scientists who conducted the experiment said that Dolly was an exact duplicate of the sheep who donated the adult cell. (news.bbc.co.uk/onthisday/hi/dates/stories/february/22/newsid_4245000/4245877)
Dolly was born in 1997 and lived till February 2003, when she was euthanized after being diagnosed with a lung condition and arthritis indicating premature aging.
The cloning process does raise some ethical considerations-not the least of which being how viable cloned creatures (animal or human) may be as compared to naturally grown species. Since we tend to be prejudiced against the taking of human life (justly so), ethical and cultural considerations do come into play should human cells be used to create life using a similar process to that which produced Dolly, the sheep. Would the creatures thus produced have intelligence similar to ordinary humans? (Dolly seemed to be a very ordinary sheep.) If fetuses thus created should be defective, what is the ethical approach? Are they to be considered as human as a baby created by artificial insemination?
On the positive side of this sort of experimentation, it has been speculated that it might be possible to re-create species now extinct where specimens have been conserved by being frozen into glaciers. To date, insufficient genetic material of a viable quality has been recovered from frozen mammoths. Two possible methods of cloning a mammoth might be possible: using frozen sperm, in a method similar to artificial insemination; or using a cell to fertilize a modern elephant egg. The first would create an elephant/mammoth hybrid, the second a duplicate mammoth. The mere thought has raised a storm of controversy. Should these once-living creatures be re-created? Or should we leave well-enough alone, and be content to have seen the frozen carcasses?
Further questions include: how would cloning effect population? What would be the legal status of a clone? There is even the theological question, would such beings have souls? No one really has answers at this time.
Science fiction has frequently explored these questions. It has also taken a look at what would happen if humans cloned replacement bodies of themselves. Would the resultant beings be considered an extension of the human (like an arm or a leg) or would their status be more like that of naturally born children? An herein lies the true rub of the cloning question.
Till we know more of the process, many questions are moot. Not investigating this area of growth and reproduction is rather like hiding our heads in the sand and insisting it doesn't exist. By default, cruel as it may seem, this must mean using animals, since the use of human tissue raises questions far too delicate.
Will animal experimentation lead to cloning humans? The jury really is still out on that one. Perhaps the question we should ask is, would it be necessary to grow a whole human to get replacement parts? Because that is the Pandora's box that holds all the troubles for this particular issue.