Imprecisely multiplying two analog numbers should not require 10^5 times the minimum bit energy in a well-designed computer.
A well-designed computer would also use, say, optical interconnects that worked by pushing one or two photons around at the speed of light. So if neurons are in some sense being relatively efficient at the given task of pumping thousands upon thousands of ions in and out of a depolarizing membrane in order to transmit signals at 100m/sec—every ion of which necessarily uses at least the Landauer minimum energy—they are being vastly far from optimally efficient.
The moment you see ions going in and out of a depolarizing membrane, and contrast that to the possibility of firing a photon down a fiber, you ought to be done asking whether or not biology has built an optimally efficient computer. It actually isn’t any more complicated than that. You are driving yourself further from sanity if you then try to do very complicated reasoning about how it must be close to the limit of efficiency to pump thousands of ions in and out of a membrane instead.
Imprecisely multiplying two analog numbers should not require 10^5 times the minimum bit energy in a well-designed computer.
A well-designed computer would also use, say, optical interconnects that worked by pushing one or two photons around at the speed of light. So if neurons are in some sense being relatively efficient at the given task of pumping thousands upon thousands of ions in and out of a depolarizing membrane in order to transmit signals at 100m/sec—every ion of which necessarily uses at least the Landauer minimum energy—they are being vastly far from optimally efficient.
The moment you see ions going in and out of a depolarizing membrane, and contrast that to the possibility of firing a photon down a fiber, you ought to be done asking whether or not biology has built an optimally efficient computer. It actually isn’t any more complicated than that. You are driving yourself further from sanity if you then try to do very complicated reasoning about how it must be close to the limit of efficiency to pump thousands of ions in and out of a membrane instead.