Geoff Watts meets researchers looking for clues to the origins of depression as a way of finding new solutions to treating it.

In the first of two programmes Geoff talks to the father of evolutionary medicine, Randolph Nesse and asks why hasn't natural selection made us less vulnerable to psychological diseases?

Could it be that depression is in some way useful to our lives?

(Image: A depressed young boy. Credit: Science Photo Library) Show less