Alfred R. Wallace and Frank Finn

“ The general laws of heredity and variation have been proved to apply to man as well as to animals and plants; and numerous facts in the distribution of races show that man must, in remote ages at least, have been capable of constitutional adaptation to climate. If the human race constitutes a single species, then the mere fact that man now inhabits every region, and is in each case constitutionally adapted to the climate, proves that acclimatization has occurred. ”

“ In none of these cases is there any indication that acclimatization was necessary or ever took place.
On the other hand, the fact that an animal or plant cannot be naturalized is no proof that it is not acclimatized. It has been shown by C. Darwin that, in the case of most animals and plants in a state of nature, the competition of other organisms is a far more efficient agency in limiting their distribution than the mere influence of climate. We have a proof of this in the fact that so few, comparatively, of our perfectly hardy garden plants ever run wild ”

“ ACCLIMATIZATION, the process of adaptation by which animals and plants are gradually rendered capable of surviving and flourishing in countries remote from their original habitats, or under meteorological conditions different from those which they have usually to endure, and at first injurious to them. ”

“ When we get lower in the scale the adaptation is often more marked. Snakes, which are so abundant in warm countries, diminish rapidly as we go north, and wholly cease at lat. 62°. Most insects are also very susceptible to cold, and seem to be adapted to very narrow limits of temperature.
From the foregoing facts and observations we may conclude, firstly, that some plants and many animals are not constitutionally adapted to the climate of their native country only, but are capable of enduring and flourishing under a more or less extensive range of temperature and other climatic conditions ”

“ The grain is elongate and of a reddish colour, but it has a sweet smell and very pleasant taste. It is called Yu-mi, Imperial rice, because it was first cultivated in my gardens. It is the only sort which can ripen north of the great wall, where the winter ends late and begins very early; but in the southern provinces, where the climate is milder and the land more fertile, two harvests a year may be easily obtained, and it is for me a sweet reflection to have procured this advantage for my people. ”

“ The subject of acclimatization is very little understood, and some writers have even denied that it can ever take place. It is often confounded with domestication or with naturalization; but these are both very different phenomena. A domesticated animal or a cultivated plant need not necessarily be acclimatized; that is, it need not be capable of enduring the severity of the seasons without protection. The canary bird is domesticated but not acclimatized, and many of our most extensively cultivated plants are in the same category. ”

“ In addition to these examples, it is obvious that the rapid increase of English-speaking populations in the United States and in Australia is far greater than can be explained by immigration, and shows two conspicuous examples of acclimatization.
On the whole, we seem justified in concluding that, under favourable conditions, and with a proper adaptation of means to the end in view, man may become acclimatized with at least as much certainty and rapidity (counting by generations rather than by years) as any of the lower animals. ”

“ But in most cases habit, however prolonged, appears to have little effect on the constitution of the individual, and the fact has no doubt led to the opinion that acclimatization is impossible. There is indeed little or no evidence to show that any animal to which a new climate is at first prejudicial can be so acclimatized by habit that, after subjection to it for a few or many seasons, it may live as healthily and with as little care as in its native country ”

“ The excessive mortality of European troops in India, and the delicacy of the children of European parents, do not affect the real question of acclimatization under proper conditions. They only show that acclimatization is in most cases necessary, not that it cannot take place. The best examples of partial or complete acclimatization are to be found where European races have permanently settled in the tropics, and have maintained themselves for several generations. ”

“ Some of the passerine birds have been the most widely distributed, especially the house-sparrow (Passer domesticus) , which is now an integral, and very troublesome, part of the fauna in the Australasian States and in North America. It is, in fact, as notorious an example of over-successful acclimatization as the rabbit, but in Hutton and Drummond’s recent work on the New Zealand animals (London, 1905) it is not regarded in this light, considering that some very common exotic birds were needed to keep down the insects, which it certainly did. ”

“ Mammals.—It is unnecessary here to dwell upon the world-wide distribution of the two rats Mus rattus and M. decumanus, and of the house-mouse M. musculus; their introduction has always been involuntary. Similarly nearly all our domestic mammals except the sheep have become feral somewhere or other, whether by intentional liberation or by escape; but the smaller ones more than the larger, such as pigs, goats, dogs and cats. This has been especially the case in Hawaii and New Zealand; in America, Australia and Hawaii, horses and cattle are also feral. Feral pigs are numerous in New Zealand. ”

“ The Jews are a good example of acclimatization, because they have been established for many centuries in climates very different from that of their native land; they keep themselves almost wholly free from intermixture with the people around them; and they are often so populous in a country that the intermixture with Jewish immigrants from other lands cannot seriously affect the local purity of the race. ”

“ The first step would be, to obtain seed from healthy trees growing in the coldest climate and at the greatest altitude in its native country, sowing these very largely, and in a variety of soils and situations, in a part of France where the climate is somewhat but not much more extreme. It is almost a certainty that a number of trees would be found to be quite hardy. As soon as these produced seed, it should be sown in the same district and farther north in a climate a little more severe. ”

“ Negroes, for example, who have been for three or four generations acclimatized in North America, on returning to Africa become subject to the same local diseases as other unacclimatized individuals. He well remarked that the debility and sickening of Europeans in many tropical countries are wrongly ascribed to the climate, but are rather the consequences of indolence, sensual gratification and an irregular mode of life. Thus the English, who cannot give up animal food and spirituous liquors, are less able to sustain the heat of the tropics than the more sober Spaniards and Portuguese. ”

“ The yak of Thibet cannot long survive in the plains of India, or even on the hills below a certain altitude; and that this is due to climate, and not to the increased density of the atmosphere, is shown by the fact that the same animal appears to thrive well in Europe, and even breeds there readily. The Newfoundland dog will not live in India, and the Spanish breed of fowls in this country suffer more from frost than most others. ”

“ In more recent times, the conditions have been so greatly changed by immigration, that the later statistics cease to have a definite meaning with regard to acclimatization. We have here a population which doubled itself every twenty-two years; and the greater part of this rapid increase must certainly be due to the old European immigrants. In the Moluccas, where the Dutch have had settlements for 250 years, some of the inhabitants trace their descent to early immigrants ”

“ The military adventurers, who have often risen to high or even supreme rank in Peru, have not seldom been of mixed race, and fear or favour has often availed to procure them an alliance with the oldest and purest-blooded families. ”

“ If she thus bring a good dowry to her husband, he does not care to inquire, or is not sensitive, about the mode in which it was acquired. The consequence of this indiscriminate sexual intercourse, especially if much prolonged, is to diminish, in some cases to paralyse, the fertility of the female. And as among people of mixed race it is almost universal, the population of these must fall off both in numbers and quality. ”

“ It is true that most terrestrial animals are restricted to countries not possessing a great range of temperature or very diversified climates, but there is reason to believe that this is due to quite a different set of causes, such as the presence of enemies or deficiency of appropriate food. When supplied with food and partially protected from enemies, they often show a wonderful capacity of enduring climates very different from that in which they originally flourished. ”

“ Now there is a zone of the equatorial Andes, ranging between about 4000 and 6000 feet altitude, where the very best flavoured coffee is grown, where cane is less luxuriant but more saccharine than in the plains, and which is therefore very desirable to cultivate, but where the red man sickens and dies. Indians taken down from the sierra get ague and dysentery. Those of the plains find the temperature chilly, and are stricken down with influenza and pains in the limbs. ”

“ Birds.—The introduction of mammals has been largely influenced by economic conditions, when, indeed, it was not absolutely accidental and unavoidable; but in the case of birds it has been more gratuitous, so to speak, in many cases, and hence is looked upon with especial dislike by naturalists. The domestic birds have comparatively seldom become feral, doubtless, as C. Darwin points out, from the reduction of their powers of flight in many cases. ”

“ Different Degrees of Climatal Adaptation in Animals and Plants.—Plants differ greatly from animals in the closeness of their adaptation to meteorological conditions. Not only will most tropical plants refuse to live in a temperate climate, but many species are seriously injured by removal a few degrees of latitude beyond their natural limits. ”

“ The guinea-fowl, however, has long been in this condition in Jamaica and St Helena, and the fowl in Hawaii and other Polynesian islands. The pheasant has been naturalized in the United States, New Zealand, Hawaii and St Helena. Its naturalization in western Europe is very ancient, but the race supposed to have been introduced by the Romans (Phasianus colchicus) has been much modified within the last century or two by the introduction of the ring-necked Chinese form (P. torquatus) , which produces fertile hybrids with the old breed. ”

“ By degrees the fecundity improved, and in about twenty years became equal to what it is in Europe. The same author tells us that, according to Garcilaso, when fowls were first introduced into Peru they were not fertile, whereas now they are as much so as in Europe. C. Darwin adduced the following examples. Merino sheep bred at the Cape of Good Hope have been found far better adapted for India than those imported from England; and while the Chinese variety of the Ailanthus silk-moth is quite hardy, the variety found in Bengal will only flourish in warm latitudes. ”

“ But in looking through the long series of volumes of Reports published by this society, there is no sign that any systematic attempt at acclimatization has even once been made. A number of foreign animals have been introduced, and more or less domesticated, and some useful exotics have been cultivated for the purpose of testing their applicability to French agriculture or horticulture; but neither in the case of animals nor of plants has there been any systematic effort to modify the constitution of the species, by breeding largely and selecting the favourable variations that appeared. ”

“ Their sons are big, stout men, but when they lead inactive lives are apt to become fat and sluggish. Those of them, however, who have farms in the savannahs and are accustomed to take long rides in all weathers, and those whose trade obliges them to take frequent journeys in the mountainous interior, or even to Europe and North America, are often as active and as little burdened with superfluous flesh as a Scotch farmer. ”

“ Attempts have also been made to naturalize continental insects in Britain, in places where the proper food-plants abound and the conditions seem generally favourable, but in no case do they seem to have succeeded. Even a plant like the potato, so largely cultivated and so perfectly hardy, has not established itself in a wild state in any part of Europe. ”