Researchers have just shown that pregnant female mice with low iron levels can lead to the development of male embryos that develop ovaries, regardless of their genetics. This discovery could have significant implications for our understanding of sex determination, and it’s thought to be the first time environmental factors have been documented to influence the process in mammals.

Sex in mammals is generally thought of as determined at the point when the sperm fertilizes the egg, but for a short while, the embryo exists in an undifferentiated state that is neither male nor female, as far as the gonads go. According to conventional interpretations, after this period, the embryo typically goes on to develop into either a male or female based on its genetics – if the embryo had a Y chromosom

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