Anthropologists have at last learned to apply to man the laws which are found to govern the spread and survival of any other species. We have finally awakened to the fact that every character possessed by a species has been evolved by natural selection to enable it to survive. A very long time ago, biologists found that animals and plants were distributed in zones and that a form never went beyond its zone, whose boundaries were approximately the isothe mals.* That is, forms spread east and west, but not north and south. It was soon found that each was so fitted to its zone by its own physical characters, that it could not go out without fatal results, omitting, of course, forms which are able to migrate annually to escape seasonal extremes.
Agassiz long ago noticed that the type of man which inhabited any one of the zoological zones was entirely different from those in the other zones. He knew that each type was thus fitted to reside in his own locality and unable to acclimatize elsewhere, but he never accepted Darwin's discovery of the plasticity of species, never understood any of the basic laws of evolution, and could not account for man's presence in these zones. He got over the difficulty by the very absurd assumption that there was a separate creation of man in each zoological zone - an Adam and Eve for every race, negroes, Asiatics, Americans, Europeans, etc. We now know that man and other species resemble glaciers in their plasticity, for though apparently hard, rigid and unchangeable, yet they are molded like clay into new forms by very slow migrations or changes in environment, a process extending over immense ages and really resulting in a new type adjusted to the new climate and unable to return to the ancestral home.
* "Smithsonian Report," 1891.
We can explain this best by taking up racial characters, one by one, and showing why they are beneficial in one place and fatal in another. For instance, the shape and size of the nose and position of the nostrils are now fairly well proved to be results of selection of the fittest variations. In the tropics where the air is hot and therefore rarefied, so that more of it is necessary, it is essential that there should be no impediments to the air currents. The nostrils are therefore open and wide and the nose very flat. Such a nose is fatal in cold countries, as it permits masses of cold air to flood the air passages and irritate the lining membrane. In cold places it is necessary that the nose should have much warming surface, and the nostrils are slender slits to admit the air in ribbon-shaped streams easily warmed. The air, being cold, is concentrated, and less of it is needed than in the tropics. Hence, there is a selection of the slender nosed types in the North. The nasal index or width of nose divided by the length, gradually increases as we go to hotter countries, where we find some races with index much greater than 1,000, i.e., width greater than length. It is now many years since it was first pointed out that the open tropical nostril was one reason for so much pulmonary trouble of negroes out of the tropics.
In like manner a small slender body with weak muscles is best for the tropics, as it is far easier to keep cool than a huge or fat body so necessary for warmth in cold climates. So we see selection working in this line, but the survival of small men in the tropics as the most fit is not noted until we compare them with our own big men. When we organized the Havana police force we had to lower the standard, as few native Cubans would have been accepted. In the Philippines, the native municipal police, are tiny fellows, four of whom are needed to arrest a white man. In Jamaica it is stated that more than half the men who volunteered for the Boer war, were rejected as physically below the standard for militia. Likewise, as we go south in Europe, the stature gradually diminishes from the Scotch to the little Mediterranean folk.
After the declaration of the Spanish war the writer was engaged in the physical examination of the volunteers of a Southern State, and was painfully impressed by the frailness of the recruits - men who were wiry, able to live in swamps, and resist the heat, but who were nevertheless poor specimens of the physical man. In marked contrast there were the big-bodied men of the Montana, Nebraska, Dakota, Minnesota, and Colorado regiments, compared to whom the Malays are pygmies. It reminds one quite forcibly of the astonishment of the Roman soldiers at the gigantic size of the Northern tribesmen. Big men, as a rule, with a few notable exceptions, have proved to be unsuited for tropical climates. It is a well-known fact that these beefy types do not last in India like the undersized campaigners such as Lord Roberts. Explorers like Livingston, Stanley and Johnston are not big men, and some of them are below par physically. Quite a number of American officers who were of great musculature have been seriously damaged by Philippine service, while little men stand it well, as a rule. There are a few tall tropical races to be sure, but they are slender - never beefy. It is no wonder, then, that the heavy, big men of the North should die out when they try to colonize in the tropics, for they cannot become smaller, which is the only possible way for them to be adjusted to the climate. Dr. W. Hartigan has gone into this subject quite extensively,* and he emphasizes the fact that big men are out of place.