Can’t whistle? It’s not you, it’s mouth geometry.

There’s a video on YouTube, filmed back in 2019, where 100 random people try to whistle on camera. About half of them fail, often spectacularly. But partway through, the video flashes through the 50 or so who succeed, and something interesting jumps out: at a glance, every single one of them appears to be making the identical shape with their mouth. Look closely, and the shape is surprisingly specific. The lips pull back slightly at the corners, rather than pucker forward. A small, round o