Benjamin Franklin is alleged to have written: ‘But in this world nothing can be said to be certain, except death and taxes’. And one is sorely tempted to add ‘the colour problem’. As black people have discovered during this and previous centuries, skin colour is the most decisive and the most abused of all the physical characteristics of humankind. It determines social perceptions, value judgments and interpersonal relationships, and it can wreak havoc on an individual's sense of dignity and selfesteem.

In this book I have endeavoured to analyse the essential nature and functions of human skin colour. I have done this predominantly from a biological standpoint, although I have included a chapter on the psychosocial dimensions of the subject and also one on the possible evolutionary forces which have determined skin colour variations among populations in different geographical regions. Disorders of pigmentation receive special attention, and I have given fairly detailed consideration to the pigmentation that occurs in sites other than the skin and hair.

The field of melanin pigmentation in all its guises is awash with journal articles, monographs and books. I have generally restricted references either to the original authors or to updated reviews, as it would have been unnecessarily cumbersome to cite the multiplicity of contributors to a particular topic. An exception is where the matter under discussion is controversial, or where I expose a personal viewpoint (as I do in assessing the vitamin D hypothesis of skin depigmentation). Here I have felt obliged to furnish fuller documentation for the arguments advanced.

The problem of race and racial labelling has been one of the most taxing for me.