Some Texas State University students in Dr. McGee’s Cultural Anthropology class left the lecture hall after he said in a lesson that all living people originated in Africa. As the exiting white students left the classroom, some remaining in class reportedly called after them, “Black Lives Matter.”

The lecture started out with a message from the professor that the day’s class would be a lesson on race and it would be particularly interesting so everyone should listen, said Justine Lundy, 20. The professor began talking about the Black Lives Matter movement and how it had come about before stating that all living beings descended from east Africa.

“It was dead silent,” Lundy said, before a student retorted with a “sarcastic ‘sure.'”

My Professor just said all living ppl are descendants from Africa and ppl got up and walked out and now their arguing ??? pic.twitter.com/TNj6EDmybv — Aj (@amvrion) October 18, 2016

At that point, students began to leave the class. A few disagreeing students who didn’t leave the classroom in a huff stayed behind to argue with each other.

“A lot of people left,” said class attendee Karene Taylor, 19. “It was embarrassing.”

Lundy said she was pretty sure it was the talk of Black Lives Matter that primed students to argue and leave, even though “[McGee] wasn’t picking sides or anything — he kept reiterating that.” The African descent component was probably “the straw that broke the camel’s back,” she said.

Me in class yesterday watching all those people leave after what Prof. McGee said #TXST pic.twitter.com/yzro4IBGJR — strep curry (@_justjallday) October 19, 2016

McGee said he himself didn’t witness any outright dissent but because the class is so large, “it is possible that someone didn’t like the topic and walked out.”

He is — as his credentials, years of research and general expertise would suggest — not wrong on the subject. The so-dubbed “out of Africa” theory is widely accepted as our definitive origins by the scientific community. The University of Cambridge’s Andrea Manica and his team spent years of research comparing thousands and human skulls as recently as 2007 to prove that, yup, we all originated solely in Africa.

“As a whole, I think the group is open-minded,” McGee said. “Understanding other peoples’ perspectives is a basic part of cultural anthropology.”