Comment by api

The simple explanation is that von Neumann architecture sucks for intelligence. It's not a von Neumann machine at all. It's an analog neural network (plus other systems in operation) with colocated memory.

A more far-out explanation is that some form of stochastic quantum computing is going on, which has been proposed at many levels by biologists. There's some work being done on this idea. It would not be the discrete qubit form we are trying to do, which is impossible in a noisy wet environment, but something analog and stochastic.

Both are possible.

Also note that our current chips, in spite of the tiny feature sizes and a ton of optimization work, are not even close to the lower limit for energy cost of computation. They still are not very efficient.