Mixed Race Studies

Studies in Melanin Pigmentation of the Skin of Racial Crosses in Port Moresby

Oceania
Volume 33, Number. 4 (June, 1963)
pages 287-292

R. J. Walsh
New South Wales Red Cross Blood Transfusion Service, Sydney, Australia

A. V. G. Price
Department of Public Health, Territory of Papua and New Guinea

The colour of the skin in different populations has always been of great interest but until recently few attempts have been made to study the factors determining the nature and amount of skin pigment. Perhaps the greatest difficulty lias been the lack of a reliable method of quantitative assessment. Davenport and Davenport (1910) devised a “colour top”—a rotating disc with sectors of different colours. The areas of the sectors were varied until the blended colours on rotation corresponded to the colour of the skin. Ruggles Gates (1949) approached the problem by producing a series of coloured papers which could be matched against the skin.  These methods, however, did not permit separate analysis of the multiple factors contributing to skin colour (haemoglobin and bilirubin contained in the skin, and carotene pigments, for example). Reflectance measurements of light at various wavelengths have therefore been used by a number of workers (Wiener. 1945 ; Harrison, 1957 ; Baraicot, 1958).

During a recent visit to New Guinea measurements were made of the reflectance of light from the skin of various subjects. A photo-electric reflectometer was used with a filter having maximum transmission at 650 millimicrons. The instrument was adjusted with a rheostat so that a meter reading of 100 corresponded to the reflectance from a magnesium oxide surface.  This instrument is described in another paper (Walsh, 1963) and reasons are given for believing that the reflectance value is related to the melanin content of the skin. Batnicot (1958) also concluded that the reflectance value at this wavelength is a measure of the melanin pigment.

There is now clear evidence that melanin is produced by the melanotytes of the skin from the amino acids phenylalaninc and tyrosine. In the initial stages of this production the copper-containing enzyme, tyrosinase, is important. Absence of tyrosinase, but not of melanocytes, is responsible for albinism and a deficiency of tyrosinase is probably the basis of the pathological condition known as vitiligo, A number of physical conditions, of which the most important is exposure to ultraviolet light, can increase the melanin content of the skin, and some chemical conditions inhibit production. These factors have recently been reviewed by Fitzpatrick and Szaba (1959).

However, there is no information available as to what determines the varying amounts of melanin in human skin of different ethnic groups. Obviously genetic factors must be responsible because there are great differences between people of…

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