Brain evolution:

1. Simple nerve cells connecting sensing cells to acting cells.

2. Learned responses, reinforced by values such as "eating is good" and "injury is bad".

3. Must solve the credit assignment problem (CAP), how to reinforce behaviors when rewards come much later, and multiple behaviors precede rewards.

4. Need to simulate the world to solve this efficiently - that is process experiences that are not currently occuring - this is the root of consciousness.