BEAVERTON, Ore.: The science of cloning climbed a little higher on the evolutionary tree with the announcement that scientists at the Oregon Regional Primate Research Center in Beaverton have successfully cloned a rhesus monkey. Unlike Dolly, the wonder sheep who was cloned from an adult animal, the monkeys were duplicated at the embryonic stage, a less dramatic breakthrough. But the success in cloning a primate has researchers salivating. "What we want to do is establish an immortal cell line, something like an embryonic stem cell line, where you can produce literally unlimited numbers of these things," Donald Wolf, a senior scientist at the center, said at a news conference Sunday. Those "things" figure to take some guesswork out of medical research, since scientists working with thoroughly identical subjects can be confident that results are not subject to genetic foibles. They could also reduce the number of animals that would be needed in a given experiment, making research cheaper and requiring fewer monkeys. "The downside," Wolf said, "is that this is one step in the direction of suggesting that nuclear transfer can be done in human beings," He insisted that the center has no interest in cloning a person. The twins, born in August to surrogate mothers through in vitro fertilization, can expect to live normal monkey lives of 15 to 20 years, researchers said. But huddled in the corner of their cage, hugging each other, they looked a lot like two frightened children. They're not the only ones who are worried.