Genetic Algorithms and Evolutionary Computation

"A field-programmable gate array, or FPGA for short, is a special type of circuit board with an array of logic cells, each of which can act as any type of logic gate, connected by flexible interlinks which can connect cells. Both of these functions are controlled by software, so merely by loading a special program into the board, it can be altered on the fly to perform the functions of any one of a vast variety of hardware devices.

Dr. Adrian Thompson has exploited this device, in conjunction with the principles of evolution, to produce a prototype voice-recognition circuit that can distinguish between and respond to spoken commands using only 37 logic gates - a task that would have been considered impossible for any human engineer. He generated random bit strings of 0s and 1s and used them as configurations for the FPGA, selecting the fittest individuals from each generation, reproducing and randomly mutating them, swapping sections of their code and passing them on to another round of selection. His goal was to evolve a device that could at first discriminate between tones of different frequencies (1 and 10 kilohertz), then distinguish between the spoken words "go" and "stop".

This aim was achieved within 3000 generations, but the success was even greater than had been anticipated. The evolved system uses far fewer cells than anything a human engineer could have designed, and it does not even need the most critical component of human-built systems - a clock. How does it work? Thompson has no idea, though he has traced the input signal through a complex arrangement of feedback loops within the evolved circuit. In fact, out of the 37 logic gates the final product uses, five of them are not even connected to the rest of the circuit in any way - yet if their power supply is removed, the circuit stops working. It seems that evolution has exploited some subtle electromagnetic effect of these cells to come up with its solution, yet the exact workings of the complex and intricate evolved structure remain a mystery (Davidson 1997)."

"However, it is trivial to show that such a claim is false, as genetic algorithms have produced irreducibly complex systems. For example, the voice-recognition circuit Dr. Adrian Thompson evolved (Davidson 1997) is composed of 37 core logic gates. Five of them are not even connected to the rest of the circuit, yet all 37 are required for the circuit to work; if any of them are disconnected from their power supply, the entire system ceases to function. This fits Behe's definition of an irreducibly complex system and shows that an evolutionary process can produce such things."

Very cool Mike!!

I remember reading about this back when it was first announced. I love this stuff.

Genetic algorithms are sweet. I never appreciated the power of natural selection until I wrote my own GA computer program.