Simulating Evolution
We have an existence proof for human level intelligence: us. We know that evolution has led to the human brain and the brains of all other species. There are two main drivers to this evolution: random mutation and natural selection. I think of this as exploitation (natural selection) vs exploration (random mutation).
It should be noted that it's also possible that some extraterrestrial intervention occurred that enabled the creation of the human brain. For example, maybe some precursor to human intelligence landed on human Earth via an asteroid.
Are we simulating this evolutionary process when we train neural networks in massive GPU clusters? If our current process of training neural networks leads to us to what is observably analogous to human intelligence, then we will have at least built a parallel and equivalent process to the natural evolutionary process that led to the Homo sapien neocortex.
What was entailed in this process? I do not know.