You might be conflating knowledge with intelligence. Remember that modern humans benefit from the discovery and dissemination of 100,000 years of human learning. For example, most of us take arithmetic for granted. We might even consider someone who does not know arithmetic to be "dumb". Same goes for algebra, trig, calc, diffeq, etc etc. But those are all "knowledge" (i.e. a trained skill), not necessarily "intelligence". Math was discovered, in fits and starts, over 1000s of years across the globe by 10s or 100s of thousands of individuals, each contributing their drop to the stream whose current carries us along. Same goes for all other areas of human knowledge.
To my awareness, there is nothing in the fossil record to suggest that an anatomically modern human (Homo sapiens), which may have first emerged as much as 500,000 years ago, would be distinguishable from currently living humans. Here's a thought experiment: We have a time machine. We travel back 500k years and abduct a pair of Homo sapiens (male and female). We transport them forward in time to our present. We cause them to breed and produce offspring. During gestation, they live in a modern environment (nutrition, shelter, etc.). At birth we take the newborn infant and give it to a modern, contemporaneous couple to raise. Is there is reason to believe it (the infant) would not emerge as a normal, modern adult?
If there is no reason, what does that imply about intelligence? Is knowledge separable from it? Or is knowledge a necessary component of it? Or is knowledge itself "intelligence"? For my part, I think it is a distinct attribute, but I assign a low probability to that belief.