What We've Covered

Sex isn't one switch but a stack of layers:

• Six markers contribute: chromosomes, gonads, hormones, internal anatomy, external anatomy, and brain structure.
• Intersex variations affect roughly 1 in 100 people by the broadest count.
• SRY is the master switch and can occasionally jump to an X chromosome, flipping the expected result.
• Hormones do the actual building once the gene fires.
• Androgen insensitivity shows genes alone don't decide: XY cells that can't read testosterone build a female-typical body.