Why do some people have such weak chins but then others are impossible to knock out?

Why do some people have such weak chins but then others are impossible to knock out? There's two reasons. The first is your brain shape. This area is called your subarachnoid space. The larger this gap is, the weaker your chin is because there's more room for your brain to rattle around in your skull. Stored in that gap is cerebrospinal fluid, which is like a cushion for your brain. And when fighters cut weight, this fluid gets depleted. And some people naturally have more fluid than others, giving them stronger chins. The second reason is the composition of white and gray matter in your brain. White matter and gray matter have different density, so when you get punched, the two parts move at different speeds, causing tears at the boundaries. Fighters with tougher gray-white matter junctions will have stronger chins. To learn more science behind fighting, follow me.