In 1871, Darwin published his controversial Descent of Man which described how man and apes had evolved from a common ancestor and opened the floodgates on the debate for human evolution.

One of the biggest questions raised against the theory was how the human mind could have evolved from a more primitive animal brain. Humans make complex decisions, are driven by emotions, impose social and moral constructs, and participate in religious activities. Surely, there was a distinction between the human mind and the animal mind. In addition, since at least the Greeks, philosophers had been arguing for a mind/body dualism, meaning the two were fundamentally other and separate.

Darwin was the first to argue that the human brain wasn't so different from the animal brain and that the mind/body distinction was an illusion.

Today, scientists are still trying to explain what the mind is and how it works. A recent article in Scientific American Mind by Professor Eric Kandel of Columbia University describes this new science of mind. (subscription required)

First, mind and brain are inseparable. The brain is a complex biological organ of great computational capability that constructs our sensory experiences, regulates our thoughts and emotions, and controls our actions. The brain is responsible not only for relatively simple motor behaviors such as running and eating, but also for the complex acts that we consider quintessentially human, such as thinking, speaking and creating works of art. Looked at from this perspective, mind is a set of operations carried out by the brain, much as walking is a set of operations carried out by the legs, except dramatically more complex.

Second, each mental function in the brain - from the simplest reflex to the most creative acts in language, music and art - is carried out by specialized neural circuits in different regions of the brain. This is why it is preferable to use the term 'biology of mind' to refer to the set of mental operations carried out by these specialized neural circuits rather than 'biology of the mind' which connoted a place and implies a single brain location that carries out all mental operations.

Third, all of these circuits are made up of the same elementary signaling units, the nerve cells. Fourth, the neural circuits use specific molecules to generate signals within and between nerve cells. Finally, these specific signaling molecules have been conserved - retained, as it were - through millions of years of evolution.