I'd wager that intelligence is nothing but a reified concept. Something which doesn't innately exist other than as an abstract concept which we have defined, to help us explain complex nature, without the need of fully understanding the underlying complexity giving rise to that nature. Like how cave men used the concept of "gods" for a satisfying explanation for why it rains - we use intelligence to ascertain why something is able to do or achieve certain things.

But fundamentally speaking, evidence suggests that the nature of reality follows simple rules. That everything obeys simple algorithmic rules. And therefore, suggests humans are just as robotic as anything else, including the earliest of computers and current "AI". We don't look at it that way, as we don't fully understand the underlying complexity which gives rise to our behavior (whereas for computers we do), so we conveniently call ourselves intelligent as a way to appease the thirst for a satisfactory explanation for our behavior, and are dissatisfied with calling current AI, as true AI.

Thus, I argue, depending on what one wants to define intelligence, AI does not innately exist and can never exist if everything truly obeys simple rules, or, AGI has existed long before humans have come to exist as it's merely a concept which we are free to define.