There's little doubt that gene editing could be one of the greatest advances in medical science, since it might let you "turn off" conditions. However, the way you test that editing is another challenge entirely -- and some scientists in China are pushing some boundaries to make it work. They've used genetic engineering to breed over a dozen macaque monkeys with a flawed gene that triggers a rare form of autism in humans. The hope is that researchers can not only study how brains function with this condition, but experiment with treatments that could be useful on people. Ideally, the researchers will use a gene editing system like CRISPR to eliminate the condition outright.