From a narrow physical aspect, pretty much everyone peaks sometime in their 20s. Your brain is a physical organ and it declines along with the rest of your body. Like your eyesight, endurance, strength, etc. It's the inevitable biological aspect of aging.
But from a holistic wider view, you don't necessarily peak in your 20s as your gains in knowledge, experience and wisdom compensates for the decline in pure physical performance.
But from a holistic wider view, you don't necessarily peak in your 20s as your gains in knowledge, experience and wisdom compensates for the decline in pure physical performance.