I don't think that "it can be emulated by computers" follows from "intelligence is a purely physical phenomenon".
Even fairly simple quantum systems (which are "purely physical phenomena") cannot be emulated by any classical computer in any meaningful sense, since the computational complexity of integrating the dynamical equations is exponential. Even if we could recruit all the atoms in the known Universe, we still couldn't build a classical computer capable of emulating many simple quantum systems.
Even if we could recruit all the atoms in the known Universe
In the past 233 years we have evolved from the first steam machine to the iPhone 5S. I would say we have a pretty good track record at overcoming miniaturization problems.
Not sure it's clear that most people don't think that. There has been a lot of articles on quantum effects in the human brain lately. e.g., http://goo.gl/Ff0elU
I was referring to the "recent discovery of quantum vibrations in microtubules inside brain neurons" which is a fact independent of any particular theory or interpretation thereof.
Even fairly simple quantum systems (which are "purely physical phenomena") cannot be emulated by any classical computer in any meaningful sense, since the computational complexity of integrating the dynamical equations is exponential. Even if we could recruit all the atoms in the known Universe, we still couldn't build a classical computer capable of emulating many simple quantum systems.