Iron deficiency in pregnant mice alters the embryo

[Catherine]

Researchers in Japan have determined that iron deficiency in a pregnant mouse can cause a male mouse to develop a female body.
It is not a frequent occurrence, but it is significant that it happens at all. This is the first time an external factor has been shown to change the development of a male embryo.

https://english.elpais.com/science-tech/...emale.html

Temperature will influence how an embryo develops in some species of reptile.
This is the first time a mammal has been shown to respond to external factors in their development of male or female bodies.
Who knows what else studies will show. Who knows what the significance of this is.