ABSTRACT
Darwin's theory of evolution is the best theory we have to explain the nature of our animal kingdom. 1 This one unifying theory explains how apparently beneficial change takes place in life forms over many generations, how seemingly close anatomical relationships exist between different animals (the hand, the flipper and the wing, for example) and how the seemingly purposeful quality of the giraffe's long neck or the woodpecker's beak could have come about. If we accept Darwin's theory then we must accept that we have descended from other mammals. If animals get depressed then it follows that we may have inherited a biological basis for depression that is older than humanity. Darwin once said ‘the major part [of our emotions], presumably including depression [my italics], are due to historical antecedents registered in the susceptible organisms. No experience of the individual can account for the strength or direction of feeling'. In other words, there is something built into the brain, an emotional programme, which has been inherited from other susceptible mammals.
