Scientists turned male mice female — and it's not the creepiest cloning trick

A team of reproductive biologists has pulled off something that sounds lifted from a sci-fi screenplay: they used CRISPR to delete the Y chromosome from male mouse embryos, producing female clones that are genetically identical to their male donors except for that missing chromosome. Takashi Ishiuchi at the University of Yamanashi and Shogo Matoba at the Riken BioResource Research Center co-led the work. Ishiuchi admitted to me the result “felt a bit like sci-fi.”

The researchers aren’t doing this for novelty. Their stated goal is conservation — imagine a species down to a handful of surviving males, with no females left to reproduce. A technique that converts male cells into female clones could theoretically rebuild a breeding population. That’s a meaningful problem. San Diego Zoo’s frozen zoo already holds cells from over 1,300 species, some collected decades ago, and cloned black-footed ferrets and Przewalski’s horses have already been born from preserved tissue.

But cloning has always straddled a line between the remarkable and the queasy. Dolly the sheep, born in 1996, proved you could clone a mammal from an adult cell. Today, companies will clone your dead dog for tens of thousands of dollars — Barbra Streisand and Tom Brady have both done it. Bioethicist Jessica Pierce calls the practice “the exploitation of the canine underclass,” and she’s not wrong. Those clones require egg donors and surrogates, animals who get no say in the process and no medical benefit from it.

Then there’s the human angle. No one has cloned a person, as far as we know. But one biotech founder has already pitched the idea of “brainless clones” — human bodies without consciousness, grown as organ banks. My colleague Antonio Regalado covered that pitch in March, and I had to stop eating lunch while rereading it. The mouse work is genuinely clever science with real conservation potential. But the same tools that could save a species could also normalize ideas most people find deeply unsettling. The next few decades will tell us which instinct wins.