The process wasn't easy. It took 127 eggs and 79 embryos to get these results, and it still required a fetus to work (Dolly was cloned from an adult). Still, it reflects progress in cloning science. The team managed the feat by injecting both a form of mRNA and an inhibitor, the combination of which improved the development of blastocysts (the structures that form the embryo) and the pregnancy rate for transplanted embryos.

Both baby macaques are healthy, the researchers said, and genetic tests confirm they really are duplicates. There could be success with cloning based on adults, too, as the team is still waiting on results from multiple pregnancies.

In theory, this makes human cloning more realistic given the genetic similarities between monkeys and our own species. However, that's unlikely to happen any time soon, if at all. There are numerous ethical objections, and not just because it would involve creating exact copies of people. Whether or not you mind cloning based on fetuses, the process currently requires many failures to get to the intended results. There's also the question of what happens with those clones that do survive into adulthood -- they may face pressure to live up to the original.

As such, monkey cloning may be limited to medical research, where having more than one monkey with the same genes could help scientists compare the results of treatments or test under specific conditions. That still won't please everyone, but it'll at least represent an ethical line in the sand that science is unwilling to cross.