Why do you think this? The idea behind the Singularity is that even an AI that starts far below human-level, but is capable of recursive self-modification, can bootstrap itself to superintelligence. We don't need to understand the human brain to create such an AI; we need only to:
A. create a the simplest of "digital animals", and
B. give it the capability to push itself into self-directed Lamarckian evolution to satisfy its preferences;
C. and have this all happen on electronic time-scales (e.g. successive "generations" being created in milliseconds or less),
and we'll likely see a Singularity.
> look at existing economic and social systems where disparate individual goals are coordinated into cooperative or conflicting action, and how the results are related to human goals and human flourishing.
"Existing economic and social systems" allow humans to cooperate with humans. The whole point of FAI research is to figure out how to make an AI that is "human"-enough that it would have cause to participate in such systems with us.
A paperclip-maximizer has nothing to gain from participating in a stock market, or an election. People do not want to be turned into paperclips, and it does not want paperclip-resources turned to human ends. Its goals are not disparate, but rather incompatible with our own.
A non-Friendly AI should not be conceptualized by your intuition as a certain kind of human that we can possibly learn to "live-and-let-live." It can, at best, be conceptualized as something like a Baby-Eating Alien[1]. Usually, though, it would seem to us something more akin to a supermassive black hole: an unlimited force that consumes many things we want and outputs nothing useful to us, that we must keep away from, and especially must avoid creating in the laboratory.