Brains aren't magical, if the laws of nature allow for them to exist in nature and we see generalized intelligence develop and get selected for repeatedly then that suggests it can be done - it's just a matter of knowing how.
It might also be a possibility that this isn't possible to be replicated in an artificial way (that is, human beings maybe aren't smart enough to ever understand their own intelligence, even using all tools to their disposition)
In a certain way, brains are so complicated that (at least for the moment) they seem quite magical to us
