* "The Present Evolution of Man".
Patrick Manson, "Tropical Diseases," says (page 81): The most fatal form of malaria, hemoglobinuric fever (twenty-five to thirty per cent, fatal) never appears in newcomers, but only after a year or two of residence with attacks of benign forms. Rarely it appears after two or three months' residence. The third year is the most susceptible. Some writers, though, declare that there is neither acclimatization or increase of susceptibility by residence (page 121). Long residence makes one less liable to severe remittants but more liable to mild attacks of malaria and to the pernicious dynamic type and hemoglobinuria. He gets chills from causes which do not affect new arrivals (chronic malaria). Acclimatization is only caring for our health (page 226). There is an acquired immunity to typhoid by long residence, and (page 235) an acquired immunity to siriasis or heat stroke, but probably this is due to greater wisdom in escaping the damage (page 354). Sprue (tropical diarrhea) is a disease of old residents. C. Firket* asserts that the longer whites remain in the tropics the greater is the mortality from malaria, instead of a lessened rate, as we would suppose, if immunity or acclimatization were possible. Win. J. Cruikshank, in an article on "Dysentery," in National Medical Review, March, 1901, shows that there is no acclimatization to this disease, but on the contrary the longer the residence the more predisposed are whites to contract it, that it is far worse in soldiers of continuous residence than in those who come and go - and states that writers in India concur in this experience.*
* Semaine Medicate, Paris, July 4. See Journal of the American Medical Association, August 4, 1900.
* Speaking of South Africa, the late Mary H. Kingsley said: "Yet remember, before you elect to cast your lot in with the West Coasters that 85 per cent, of them die of fever, or return home with their health permanently wrecked. Also remember there is no setting acclimatized to the Coast. There are, it is true, a few men out there who, although they have been resident in West Africa for years, have never had fever, but you can count them upon the fingers of one hand. There is another class who have been out for twelve months at a time, and have not had a touch of fever; these you want the fingers of your two hands to count, but no more. By far the largest class is the third, which is made up of those who have a slight dose of fever once they become extinct in a few generations according to their unfitness to their new environment.
Spain long kept possession of Cuba simply because of the degeneration of the Cubans, who were unable to fight for freedom. Many of them allowed themselves to be herded like cattle - the reconcentrados. Imagine men in cold New England being reconcentrados in 1775. The intelligent upper class is probably smaller in Cuba than anywhere in Europe or the United States, and the degraded lower classes larger in numbers.
As before explained, anthropologists once believed that populations spread in cataclysmic floods; now we are explaining ethnologic features of populations by the present slowly acting causes of race expansion by individuals, military expeditions being "merely its superficial manifestations."* It seems as though these streams of men going individually to new homes are like certain rivers which flow on, only to disappear in the desert. For in spite of the ceaseless spreading, conquering and being conquered, races of man now inhabit climates essentially the same as they have for thousands of years. In some regions we know them to be similar to the fossil remains. Even the races driven westward in England in historic times are already returning.
In the chapters on migrations, there are numerous illustrations of the degeneration of all ancient civilizations, directly due to the fact that they have resulted from the rapid immigration of brainy races into a country occupied by inferior men who have then been annihilated by the climate, leaving the civilization in the hands of the stupid autochthons, serfs, or lower classes. There are few or no traces left of the men who developed the civilizations of Chaldea, Persia, India, Egypt, Greece and Rome. The moderns are not degenerate - they are strictly normal descendants of ancient serfs. Degenerate people do not survive; a fortnight, and some day, apparently for no extra reason, get a heavy dose and die of it. A very considerable class is the fourth - those who die within a fortnight to a month of going ashore. The fate of a man depends solely on his power of resisting the so-called malaria, not in his system becoming inured to it. The first class of men that I have cited have some unknown element in their constitutions that render them immune. With the second class the power of resistance is great, and can be renewed from time to time by a spell home in an European climate. In the third class the state is that of simulative poisoning; in the fourth of acute poisoning." ("Travels in West Africa," pp. 526-7).
G. de Lapouge* shows the invariable decadence of the dominating minority of intruders in a population and their eventual elimination, and the regaining of power by the lower inferior subjugated elements. M. Leclerc, in a paper before the Congress of Ethnography,* shows how the change of environment of conquering races ruins them physically, mentally, and morally and their conditions ruin the conquered.
Dumont, in a work on "Depopulation et Civilization," a study of the causes and remedies for French decadence, after showing how all races immigrating to France die out, entirely misses the point that it is due to climatic unfitness and cannot be prevented. It can be nullified by more immigration, as has been the rule since prehistory. The land between the Seine and Loire (seventy-five miles wide between Paris and Orleans) has been called the Mesopotamia of Europe, and like its Asiatic namesake has consumed streams of men for ages. He also shows that the poor aborigines have a higher birth rate than immigrants dwelling in towns and fertile plains. He then shows that various races in a country disappear in the inverse order of their arrival, that is, the latest intruders have the highest death rate.