Hanson makes so many assumptions that defy intuition. He's talking a civilization with the capacity to support trillions of individuals, in which these individuals are largely entirely disposable and can be duplicated at a moment's notice, and he doesn't think evolutionary pressures are going to come into play? We've seen random natural selection significantly improve human intelligence in as few as tens of generations. With Ems, you could probably cook up tailor-made superintelligences in a weekend using nothing but the right selection pressures. Or, at least, I see no reason to be confident in the converse proposition.

He claims we don't know enough about the brain to select usefully nonrandom changes, yet assumes that we'll know enough to emulate them to high fidelity. This is roughly like saying that I can perfectly replicate a working car but I somehow don't understand anything about how it works. What about the fact that we already know some useful nonrandom changes that we could make, such as the increased dendritic branching observable in specific intelligence-associated alleles?

It doesn't matter. Deepmind is planning to have a rat-level AI before the end of 2017 and Demis doesn't tend to make overly optimistic predictions. How many doublings is a rat away from a human?