'It is a commonplace of science that a causal connection must exist between environment and race; in other words, the theory of evolution implies habitat as being somehow bound to have exerted a formative influence on the heredity of man as on that of any other animal kind.'

Dr. Marett's book attempts to replace this somehow with some measure of a how, to pass beyond the simple juxtaposition of the two principles of race and environment by the insertion of certain hitherto neglected intermediate links, 'some of them of a physical and others of a physiological or even psychological order', into a causal chain connecting environment and race. Its general hypothesis is 'that a natural selection for an economy of various food substances', particularly with reference to mineral deficiency, here related to climate and geology, 'has played a very important