How was Brian anew person?

Brian makes a breakthrough. Finally he realized that water refracts, and he had to aim the bow just under where it looked like the fish were in order to actually hit them. Catching his first fish was an incredible moment, and he realized that now that he had figured out how to get food, he had a way to live. He cooked that fish and more that he caught over the fire, and nothing ever tasted so good.