In humans and other animals, sex is usually determined by a single gene. However, there are claims that in some species, such as platyfish, it takes a whole “parliament” of genes acting together to determine whether offspring develop as a male or female.
In a new analysis, we took a close look at these claims. We found they describe abnormal situations, such as hybrids between two species with different sex-determining systems, or when one sex system is in the process of replacing another.
