Smell is stimulating. It stirs things up and makes us nostalgic - a wonderful word which literally means 'ache for home' - which serves to inspire new circuits in the brain.

The limits of sensory evolution in fish are defined very largely by their habitat. Water is physically supportive, carries some kinds of odour well, and is kind to sound - letting it travel several times faster than air will allow, but it inhibits other more personal kinds of communication.

The limits of sensory evolution in fish are defined very largely by their habitat. Water is physically supportive, carries some kinds of odour well, and is kind to sound - letting it travel several times faster than air will allow, but it inhibits other more personal kinds of communication.