The character of this stream will inevitably determine to a large extent the future of the American nation. The direct biological results, in race mixture, are important enough, although not easy to define. The indirect results, which are probably of no less importance to eugenics, are so hard to follow that some students of the problem do not even realize their existence.
The ancestors of all white Americans, of course, were immigrants not so very many generations ago. But the earlier immigration was relatively homogeneous and stringently selected by the dangers of the voyage, the hardships of life in a new country, and the equality of opportunity where free competition drove the unfit to the wall. There were few people of eminence in the families that came to colonize North America, but there was a high average of sturdy virtues, and a good deal of ability, particularly in the Puritan and Huguenot invasions and in a part of that of Virginia.
In the first three-quarters of the nineteenth century, the number of these "patriots and founders" was greatly increased by the arrival of immigrants of similar racial stocks from Ireland, Germany, Scandinavia, and to a less extent from the other countries of northern and western Europe. These arrivals added strength to the United States, particularly as a large part of them settled on farms.
This stream of immigration gradually dried up, but was succeeded by a flood from a new source,—southern and eastern Europe. Italians, Slavs, Poles, Magyars, East European Hebrews, Finns, Portuguese, Greeks, Roumanians and representatives of many other small nationalities began to seek fortunes in America. The earlier immigration had been made up largely of those who sought escape from religious or political tyranny and came to settle permanent homes. The newer immigration was made up, on the whole, of those who frankly sought wealth. The difference in the reason for coming could not fail to mean a difference in selection of the immigrants, quite apart from the change in the races.
Last of all began an immigration of Levantines, of Syrians, Armenians, and other inhabitants of Asiatic Turkey. Beyond this region lie the great nations of Asia, "oversaturated" with population. So far there has been little more than the threat of their overflow, but the threat is certain to become a reality within a few years unless prevented by legal restriction.
The eugenic results of immigration are partly indirect and partly direct. Direct results follow if the newcomers are assimilated,—a word which we shall use rather narrowly to mean that free intermarriage takes place between them and all parts of the older population. We shall discuss the direct results first, the nature of which depends largely on whether the newcomers are racially homogeneous with the population already in the country.
If they are like, the old and new will blend without difficulty. The effects of the immigration then depend on whether the immigrants are better or worse in average quality than the older residents. If as good or better, they are valuable additions; if inferior they are biologically a detriment.
But if the new arrivals are different, if they represent a different subspecies of Homo sapiens, the question is more serious, for it involves the problem of crossing races which are biologically more or less distinct. Genetics can throw some light on this problem.
Waiving for the moment all question as to the relative quality of two distinct races, what results are to be expected from crossing? It (1) gives an increase of vigor which diminishes in later generations and (2) produces recombination of characters.
The first result may be disregarded, for the various races of man are probably already much mixed, and too closely related, to give rise to much hybrid vigor in crosses.