The world’s first genetically edited babies have been made in China, according to a researcher who claims that twin girls born this month had their DNA altered with a powerful new tool. The researcher, He Jiankui of Shenzhen, said he altered embryos for seven couples during fertility treatments, with one successful pregnancy so far. He said his goal was to try to give the babies the ability to resist future infection with HIV. The parents declined to be identified or interviewed. His claim hasn’t been verified by other experts. But, if true, it would be a huge and controversial step in the genetic modification of human beings. “This is far too premature,” said Eric Topol, who heads the Scripps Research Translational Institute in California. “We’re dealing with the operating instructions of a human being. It’s a big deal.” Kiran Musunuru, a University of Pennsylvania gene-editing expert, said the supposed experiment was “unconscionable... an experiment on human beings that is not morally or ethically defensible.” This form of gene editing is banned in the United States.