Applied Eugenics

APPLIED EUGENICS - BY - PAUL POPENOE - EDITOR OF THE JOURNAL OF HEREDITY (ORGAN OF THE AMERICAN GENETIC ASSOCIATION), WASHINGTON, D. C. - AND - ROSWELL HILL JOHNSON PROFESSOR IN THE UNIVERSITY OF PITTSBURG

PREFACE

LIST OF ILLUSTRATIONS

INTRODUCTION

CHAPTER I - NATURE OR NURTURE?

Fig. 1.—These quadruplet daughters were born to Mr. and Mrs. F. M. Keys, Hollis, Okla., on July 4, 1915, and were seven months old when the photograph was taken. Up to that time they had never had any other nourishment than their mother's milk. Their weights at birth were as follows (reading from left to right): Roberta, 4 pounds; Mona, 4½ pounds; Mary, 4¼ pounds; Leota, 3¾ pounds. When photographed, Roberta weighed 16 pounds and each of the others weighed 16¼. Their aunt vouches for the fact that the care of the four is less trouble than a single baby often makes. The mother has had no previous plural births, although she has borne four children prior to these. Her own mother had but two children, a son and a daughter, and there is no record of twins on the mother's side. The father of the quadruplets is one of twelve children, among whom is one pair of twins. It is known that twinning is largely due to inheritance, and it would seem that the appearance of these quadruplets is due to the hereditary influence of the father rather than the mother. If this is the case, then the four girls must all have come from one egg-cell, which split up at an early stage. Note the uniform shape of the mouth, and the ears, set unusually low on the head.

Fig. 2.—Corn of a single variety (Leaming Dent) grown in two plots: at the left spaced far apart in hills, at the right crowded. The former grows to its full potential height, the latter is stunted. The size differences in the two plots are due to differences in environment, the heredity in both cases being the same. Plants are much more susceptible to nutritional influences on size than are mammals, but to a less degree nutrition has a similar effect on man. Photograph from A. F. Blakeslee.

Fig. 3.—An unusually short and an unusually tall man, photographed beside extreme varieties of corn which, like the men, owe their differences in height indisputably to heredity rather than to environment. No imaginable environmental differences could reverse the positions of these two men, or of these two varieties of corn, the heredity in each case being what it is. The large one might be stunted, but the small one could not be made much larger. Photograph from A. F. Blakeslee.

Fig. 4.—Pedigree charts of the two men shown in the preceding illustration. Squares represent men and circles women; figures underlined denote measurement in stocking feet. It is obvious from a comparison of the ancestry of the two men that the short one comes from a predominantly short family, while the tall one gains his height likewise from heredity. The shortest individual in the right-hand chart would have been accounted tall in the family represented on the left. After A. F. Blakeslee.

CHAPTER II - MODIFICATION OF THE GERM-PLASM