An interesting article from the Atlantic about how only humans have chins. Nobody knows exactly why really, but there are competing theories. At least if you get attacked and eaten by a lion you can shout “you chinless wonder!” at it before you die.
It made me think about the use of the chin in martial arts. In many ways a chin could be considered a disadvantage, as the jaw is where you want to hit somebody “square on the jaw” if you want to knock them out, and the chin makes the jaw more accessible.
I also though about martial arts that make use the chin and the only one that comes to mind is BJJ. I find I use my chin a lot to hold people in place – a bit like a third arm – in top positions. It hooks over the shoulder nicely to stop people getting up when you’re behind them slightly. It’s not one of those techniques that is taught, it just happens naturally.