There is a rare condition in humans and other vertebrates where they genetically belong to one sex but also have characteristics of the other.
Decades ago, scientists found that Oryzias latipes
(Japanese rice fish, also called medaka) often undergo sex reversal in the wild and new exploratory research
may lead to insight in humans.
In medaka fish. sex reversal involves genetically female larvae (meaning they have two X chromosomes) going on to develop male characteristics, or vice versa. Scientists had already discovered that environmental factors, such as temperature changes in the brackish and fresh waters where medaka fish live, are likely involved in their sex reversal.