It's one thing to genetically modify an organism in the lab. It's another thing entirely to spread those modifications in the wild, altering whole populations or even species. A new technology, the “CRISPR gene drive,” promises to do just that, giving human beings an unprecedented ability to fine-tune the natural world and nudge evolution in new directions. Malaria-resistant mosquitoes? Lyme-blocking ticks? Those are just a few of the applications floated so far, but the possibilities are endless. I talked to molecular biologist and “evolutionary sculptor” Kevin Esvelt, who first proposed the CRISPR gene drive, about its potential, perils and steps to ensure that we use our new powers wisely.