Turns out, it’s not just chromosomes that determine sex during fetal development. While we’ve long believed that an embryo’s sex is locked in from the moment sperm meets egg (XX for female, XY for male) new research suggests things might not be so fixed. In fact, all humans start out with the same potential. For the first six weeks of development, we all carry the foundation to become either sex. It’s only around week seven that the body switches on a biological program to form either testes or ovaries.
That in-between period has raised an intriguing question: Could environmental factors, like a nutrient deficiency, interfere with that genetic programming?
A recent Nature study from researchers at Osaka University suggests that it can — at least in mice. The team found that low iron levels in pregnant mothers can override genetic sex, turning male (XY) embryos into females (XX). The study ...
