A team at the University of California, San Diego, has just shown an evolution-warping technology called a gene a drive can work in mice. But we don’t need to worry about it escaping the lab and wreaking environmental havoc—for now, anyway.

Super inheritance: A gene drive involves adding a “selfish” gene to animals that is then passed to their offspring at a rate higher than the usual 50-50 chance.

Killer idea: Scientists think they can use gene drives to wipe out wild populations of animals with genes that are bad for them. There’s a plan to kill off malaria mosquitoes, for example, and one conservation group wants to use a gene drive to eradicate invasive mice and rats on islands, where they prey on sea birds. Others say there’s a risk the technology could get out of control.

Not so fast: The UCSD team—who used the gene-editing technique CRISPR to create the drive—had substantial difficulty in creating it (they used it to change the animals’ coat colors). And they say it only works on females, not males. That means a mouse gene drive probably can’t work in the wild—at least not yet—because it’s not efficient enough.

“Both the optimism and concern that gene drives may soon be used to reduce invasive rodent populations in the wild is likely premature,” write Kimberly Cooper and colleagues in a preprint posted July 4 on Biorxiv. Instead, the scientists say the technique will be useful for creating more sophisticated mouse models of human disease.