CHAPTER XV

THE INFLUENCE OF THE ENVIRONMENT UPON MAN 336

(1) Among men there is no normal environment. (2) The effect of exercise, (3) of general conditions, (4) and of climate. (5) Huntington’s theory of optimum climatic conditions. (6) The effect of food, altitude, &c. (7) Statistical results. (8) Effect of disease. (9) Evidence derived from twins. (10) Conclusion that modifications, with the exception of those produced by disease, are not of great importance, though of more importance than in the case of species closely allied to man.