The amount of variability is most conveniently measured by a coefficient known as the standard deviation σ, which is small when the range of variation is small, but large when diversity of material is great. The following comparisons of the point at issue may be made.[202]
| Avg. | σ | ||
|---|---|---|---|
| 100 | American men | 78.3 | 3.1 |
| 1011 | Cambridge graduates (English males) | 79.85 | 2.95 |
For the men, little difference is discernible. The Old Americans are slightly more long-headed than the English, but the amount of variation in this trait is nearly the same on the two sides of the ocean.
The average of the American women is 79.5 with σ = 2.6. No suitable series of English women has been found for comparison.[203] It will be noted that the American women are slightly more round-headed than the men; this is found regularly to be the case, when comparisons of the head form of the two sexes are made in any race.
In addition to establishing norms or standards for anthropological comparison, the main object of Dr. Hrdlička's study was to determine whether the descendants of the early American settlers, living in a new environment and more or less constantly intermarrying, were being amalgamated into a distinct sub-type of the white race. It has been found that such amalgamation has not taken place to any important degree. The persistence in heredity of certain features, which run down even through six or eight generations, is one of the remarkable results brought out by the study.
If the process could continue for a few hundred years more, Dr. Hrdlička thinks, it might reach a point where one could speak of the members of old American families as of a distinct stock. But so far this point has not been reached; the Americans are almost as diverse and variable, it appears, as were their first ancestors in this country.
APPENDIX D
THE ESSENCE OF MENDELISM
It is half a century since the Austrian monk, Gregor Mendel, published in a provincial journal the results of his now famous breeding experiments with garden peas. They lay unnoticed until 1900, when three other breeders whose work had led them to similar conclusions, almost simultaneously discovered the work of Mendel and gave it to the world.