602 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1909. 
number of productive females, a sort of accommodation takes place 
in each case between the potential rate of increase of the group and 
its means of subsistence, or chance of survival. More females at 
birth is the response of nature to the increasingly favorable environ- 
ment, or condition. In-and-in-breeding is undoubtedly injurious 
to the welfare of any species. As such, according to Westermarck, 
it 1s accompanied by a decline in the proportion of females born. 
This is the expression of nature’s disapproval of the practice, while 
intermixture tends, contrariwise, to produce a relative increase of 
the female sex. Certain it is that an imposing array of evidence 
can be marshaled to give color to the hypothesis. My suggestion at 
this point is that here in the radical intermixture just now beginning 
in the United States, and sure to assume tremendous proportions in 
the course of time, will be afforded an opportunity to study man in 
his relation to a great natural law in a way never before rendered 
possible. Statistical material is at present too meager and vague, but 
one may confidently look forward to such an improvement in this 
regard that an inviting field of research will be exposed to view. 
The significance of the rapidly increasing immigration from 
Europe in recent years is vastly enhanced by other influences in the 
United States. A powerful process of social selection is apparently 
at work among us. Racial heterogeneity, due to the direct influx of 
foreigners in large numbers, is aggravated by their relatively high 
rate of reproduction after arrival; and in many instances by their 
surprisingly sustained tenacity of life, greatly exceeding that of 
the native-born American. Relative submergence of the domestic 
Anglo-Saxon stock is strongly indicated for the future. ‘ Race 
suicide,” marked by a low and declining birth rate, as is well known, 
is a world-wide social phenomenon of the present day. Nor is it by 
any means confined solely to the so-called “ upper classes.” It is 
so notably a characteristic of democratic communities that it may 
be regarded as almost a direct concomitant of equality of opportunity 
among men. To this tendency the United States is no exception; 
in fact, together with the Australian commonweaiths, it affords one 
of the most striking illustrations of present-day social forces. Owing 
to the absence of reliable data it is impossible to state what the actual 
birth rate of the United States as a whole may be; but for certain 
Commonwealths the statistical information is ample and accurate. 
From this evidence it appears that for those communities, at least, to 
which the European immigrant resorts in largest numbers the birth 
rate is almost the lowest in the world. France and Ireland alone 
among the great nations of the earth stand lower in the scale. This 
relativity is shown by the following table, giving the number of births 
in each case per thousand of population: 
