In recent months, bathrooms have become a topic of heated debate. At issue is who should be allowed into which restroom. The Obama administration says public school students should be able to use facilities that correspond with their chosen gender identity. Opponents say they’re worried about the dangers of a gender free-for-all in the nation’s restrooms. Thursday, we’re talking about the clash over sex-segregated bathrooms. We’ll also ask how we came to have gendered lavatories in the first place.