Bill Nye, who has been recently spending time yelling at people that gender is fluid and has nothing to do with DNA, used to tell everyone that science says chromosomes determine if a person is a boy or a girl.

In an episode of his show “Bill Nye the Science Guy,” circa 1996, the message is loud and clear: biology says chromosomes determine if people are male or female.

“Inside each of ourselves are these things called chromosomes, and they control whether we become a boy or a girl,” a teenage narrator explains. “There are only two possibilities: ‘XX,’ a girl, or ‘XY,’ a boy.”

Bill Nye the Science Guy on gender, circa 1996. (Season 4, Episode 8) "[Chromosomes] control whether we become a boy or a girl." pic.twitter.com/oK2xPbRiKx — Ian Miles Cheong (@stillgray) April 28, 2017

You can watch the full episode here. The bit about chromosomes starts at the 7:30 minute mark.

This message contradicts the liberal malarkey Nye has been pushing recently. In a recent episode of his new Netflix show, a spin-off of his show from the 1990s, Nye teamed up with Rachel Bloom of “Crazy Ex Girlfriend” to explain why gender is oh-so-fluid and not at all tied to one’s DNA.

The real question is clear: Why is Nye campaigning so hard against science lately?