Fish, insects, crustaceans, and even some plants possess the ability to change the sex of their offspring before they are born.
It's a genetic skill mammals lack. Or did.
A new study reveals a genetic system in mammals that enables two animals to mate and produce only females. A similar system based on identical principles would produce only males.
This proof of concept is in mice - an instance where a mouse study is actually valid - but the real benefit is for agriculture, where farmers may want dairy cows and egg-laying chickens and not have to deal with random chance.