You're forgetting a few billion years of evolution; we come with a fair amount of pretraining encoded in our DNA
Its also not given or constant, modern humans are super young in the evolutionary scale and very different even if very similar from other animals. Funny enough we might have cracked the difference (language processing) but are still very far in the rest for AGI.
The amount of knowledge/behavior that is innate - encoded in our DNA - is pretty minimal, consisting of things like opposite sex sexual attraction, fear of heights, fear of snakes, disgust at rotting smell, etc - basic survival stuff.