Researchers at the Chinese Academy of Sciences say baby mice have now been made with two mums and no dad.
It took a substantial feat of genetic engineering to break the rules of reproduction.
The scientists said the "bimaternal" animals were healthy and went on to have pups of their own.
But there was bad news on the all‑male front.
Mice with double‑dads were attempted, but died within days of being born.
The BBC reports the researchers were trying to answer fundamental questions about why we have sex.
Mammals, including us, can make babies only through sexual reproduction ‑ aka you need an egg from mum and a sperm from dad.
But the rest of the natural world doesn't play by the same rules; some female fish, reptiles, amphibians and birds can go it alone.
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