Let’s consider the human brain:
The human brain contains about 10 billion nerve cells, or neurons. On average, each neuron is connected to other neurons through about 10 000 synapses. (The actual figures vary greatly, depending on the local neuroanatomy.) The brain’s network of neurons forms a massively parallel information processing system. This contrasts with conventional computers, in which a single processor executes a single series of instructions.
Against this, consider the time taken for each elementary operation: neurons typically operate at a maximum rate of about 100 Hz, while a conventional CPU carries out several hundred million machine level operations per second. Despite of being built with very slow hardware, the brain has quite remarkable capabilities:
- its performance tends to degrade gracefully under partial damage. In contrast, most programs and engineered systems are brittle: if you remove some arbitrary parts, very likely the whole will cease to function.
- it can learn (reorganize itself) from experience.
- this means that partial recovery from damage is possible if healthy units can learn to take over the functions previously carried out by the damaged areas.
- it performs massively parallel computations extremely efficiently. For example, complex visual perception occurs within less than 100 ms, that is, 10 processing steps
- it supports our intelligence and self-awareness. (Nobody knows yet how this occurs.)
The question we will next consider is whether there are features of the cell’s design, not necessary for cellular life, yet necessary to make a brain.