The assumption is that humans are the only primates capable of speech, but one researcher who’s been studying Koko the gorilla says apes might be a lot closer to being able to vocalize their thoughts than we guessed.

“I went there with the idea of studying Koko’s gestures, but as I got into watching videos of her, I saw her performing all these amazing vocal behaviors,” Marcus Perlman, a postdoctoral psychology researcher at the University of Wisconsin-Madison told Phys.

Many of her breathing behaviors were previously considered impossible. If Koko, who has spent decades living with humans at the Gorilla Foundation, developed them over years of interaction, it would blow up another assumption — that apes can’t learn new vocal or breathing behavior.

Science Daily reports that Koko is not considered to be exceptional, just a primate who grew up in a wildly different environment. If true, we have to rethink some assumptions about human evolution, because it’s likely the ability to develop speech was there all the way back 10 million years ago when we shared our last common ancestor with gorillas.