I don't understand what you mean by this. The human brain has not meaningfully changed, biologically, in the past 40,000 years.
We, collectively, have built a larger base of knowledge and learned to cooperate effectively enough to make large changes to our environment. But that is not the same thing as recursive self-improvement. No one has been editing our genes or performing brain surgery on children to increase our intelligence or change the fundamental way it works.
Modern brains don't work "better" than those of ancient humans, we just have more knowledge and resources to work with. If you took a modern human child and raised them in the middle ages, they would behave like everyone else in the culture that raised them. They would not suddenly discover electricity and calculus just because they were born in 2025 instead of 950.
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And, if you are talking specifically about the ability to build better AI, we haven't matched human intelligence yet and there is no indication that the current LLM-heavy approach will ever get there.