Here we see an unqualified doctrine of the plasticity of human nature, physical and mental, under the influence of climate and geographical environment, such as his description of the Scythians has led us to suspect already. An adjacent passage adds the further theoretical point, that even acquired variations of wholly artificial character may become hereditary in time. The case is that of the Macrocephali, whose haunts unfortunately are not specified.[105] ‘In the beginning it was their custom which was chiefly responsible for the length of their head, but now, their mode of growth too reinforces their custom. For they regard as best bred those who have the longest head.’ Then he describes how the heads are remodelled in infancy by massage and bandaging; and proceeds: ‘At the beginning the practice itself had the result that their mode of growth was of this kind. But as time went on, it came to be inbred so that their law was no longer compulsory:’ ἐν φύσει ἐγένετο, ὤστε τὸν νόμον μηκέτι ἀναγκάζειν. He then explains that just as baldness and grey eyes and physical deformities are hereditary (for he makes no distinction between natural and acquired varieties), ‘now similarly they do not grow at all as they did before: for the practice has no longer any force, through the people’s own neglect of it.’ The bearing of this passage, and the doctrine which it expounds, on Herodotus’ account of the Colchi, will be obvious at once. Clearly, if the proportions of the head can be affected by artificial pressure, reinforced by social selection of the most successfully deformed--that is to say, of the individuals with the softest skulls; and if, as Hippocrates clearly thought, the colour of the eyes, and presence or absence of hair, were characters of the same order of transmissibility; and if, further, as in the case of the Phasians, skin-colour and bodily proportions resulted from climate and occupation; then clearly it mattered comparatively little to Herodotus whether the Colchians were woolly-haired or not. Woolly hair, like baldness, could be inherited indeed; but it could also be superinduced, like macrocephaly, by assiduous curling, or, as every barber knows, by the subtler influence of atmospheric moisture. It is consequently not only because, as suggested above, there were other woolly-haired people, besides the Egyptians and Colchians who were in question, that Herodotus has recourse to other evidence than that of physique to prove their identity: it is because, for fifth-century anthropology, the evidence of physique itself did not justify conclusions of appreciably higher validity than those which resulted from the comparison of industries or customs.