The Effects of Tropical Light on White Men

An excerpt from the Preface: This work had its origin in an attempt to prove or disprove the theory announced by von Schmaedel in a paper read before the Anthropological Society of Munich in 1895, tnat skin pigmentation of man was evolved for the purpose of excluding the dangerous actinic or short rays of light which destroy living protoplasm. It gave, at once, the reasons for the evolution of nigrescence and blondness, the reasons why Europeans have always failed to...
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An excerpt from the Preface:

This work had its origin in an attempt to prove or disprove the theory announced by von Schmaedel in a paper read before the Anthropological Society of Munich in 1895, tnat skin pigmentation of man was evolved for the purpose of excluding the dangerous actinic or short rays of light which destroy living protoplasm. It gave, at once, the reasons for the evolution of nigrescence and blondness, the reasons why Europeans have always failed to colonize in the tropics and why blonds disappear when they migrate from their northern home, and finally gave rise to practical hygienic rules for white men compelled to reside in the tropics. The suggestions were of such inestimable value, providing his theory was correct, that a systematic search was instituted for data, and as these discoveries proved the correctness of the theory, a synopsis was presented to the Manila Medical Society, March 7, 1904, but the full paper grew to its present size, as it was necessary to prove the theory conclusively. Our anthropologists have not so far taken the matter up exhaustively, though every now and then there is a short paper on the subject. Medical literature has ignored the matter almost exclusively, although it is of the greatest importance to all blonds in the United States. Popular scientific literature still ignores the real issue. For instance, there is a discussion in the Scientific American of August 20 and October 15, 1904, as to the reason for man's pigmentation and not one of the writers has touched on the effects of the shorter sun's rays, and consequently they are wholly unable to reconcile the facts with theories as to absorption and radiation of the longer rays of the red half of the spectrum and the infra-red.