Scientists have cloned adult humans, producing early stage embryos with DNA that matches the original human. These embryos do not have the potential of reaching maturity. Efforts to produce viable embryos from adult monkeys after years of effort remain unsuccessful. (Gautam Naik, "Scientists Make First Embryo Clones From Adults," Wall Street Journal, April 17, 2014)
The early stage embryos hold exciting promise for producing cells identical to those found in the cloned individual, offering hope of new treatments for diseases that include Alzheimer's and heart attacks. The older a diseased person is, the greater the potential for cell replacement therapy. Research in this area had largely stalled because the only source of cells has been early stage embryos. Anti-abortion groups contend that using such an embryo, because it destroys the embryo, is equivalent to taking a human life (murder, in their estimation).
Production of human embryo clones raises two ethical questions. In the nearer term, the cloning—if scientists are successful in producing viable embryos—poses questions about humans producing designer humans, altering clones to include or delete particular genes. This obviously has great possibilities for abuse and most ethicists oppose, for good reasons, this prospect. Longer term, if cloning became widely practiced could adversely affect the human gene pool in ways analogous to inbreeding. Species that reproduce sexually tend to flourish for a longer period, have more complexity, and live in a greater variety of settings that species that reproduce asexually.
Research to improve human life using cells produced in processes that depend upon non-viable cloned embryos merits support because of its potential for improving human life. However, the research should occur with strong controls to prohibit producing viable embryos, a morally disturbing prospect.
Incidentally, even if scientists can someday produce viable human cloned embryos, such an embryo, if it matured into an adult human, would differ from the original in important ways. Experience, nutrition, and numerous other environmental factors significantly influence who a person is; no human is simply the produce of his or her genes.