Misconception Concerning Human Heredity 



275 



set somewhat more deeply than they 

 originally grew. 



It is evident that the commercial 

 possibilities of this fruit are excellent. 

 All who are growing it state that the 



supply far exceeds the demand. Its 

 culture is simple, it produces its fruit 

 in the greatest abundance, and the 

 prices obtained have been very satis- 

 factorv. 



A Common Misconception Concerning Human Heredity 



' ' Important as the heredity which has 

 stamped its hall-mark upon an organism 

 or an individual may be, there is another 

 factor constantly at work in molding 

 it, namely, its environment. The fin- 

 ished article, be it vegetable-marrow 

 or man, is the resultant in a parallelo- 

 gram of forces, the factors of which are 

 heredity, or what it brings with it into 

 the world, and environment, or the 

 play of world forces upon it. So far 

 as it concerns the individual, heredity 

 stops at his birth, though the burden 

 or the treasure it may have bound upon 

 his shoulders is sometimes not revealed 

 till after a long period of years. Its 

 greatest influence is antenatal. The 

 environment of the parents may affect 

 the heredity of the child for' good or ill, 

 but the major part of the effect of envi- 

 ronment is a post-natal and personal 

 matter. 



' ' A leek or a lily grown in the open air 

 has green leaves, but if the plant is 

 forced to live in a dark cellar where the 

 sunlight cannot reach it, its leaves are 

 white. It requires the energetic touch 

 of the sun to enable it to elaborate the 

 green chlorophyll, which gives it its 

 verdure. Or it may be grown in the 

 sunlight, in soil from which all traces of 

 iron have been removed, and its leaves 

 will remain pale. But if a little iron be 

 added to the soil the leaves will quickly 

 assume their natural hue. Here we 

 arc dealing with only one factor in the 



environment; but in nature, as a rule, 

 the circumstances are more complex. 



"The response to the conditions of 

 environment are well shown by the 

 behavior of certain Alpine plants. If 

 taken from their natural habitat and 

 cultivated in the lowlands, they undergo 

 material alterations in character. They 

 grow to a greater height and their 

 leaves expand in length and breadth. 

 So long as the plant remains in the low- 

 lands it will exhibit in each successive 

 generation these altered characters. 

 But if one of the plants is transferred 

 once more to its original habitat, high 

 up upon the bleak mountains, it will 

 once more assume the Alpine charac- 

 teristics, which continue to persist so 

 long as the plant or its descendants live 

 under the same conditions. ... In 

 the nature of things it is perhaps to be 

 expected that the influence of environ- 

 ment should make itself felt in plant 

 life ; but it plays a great part in produc- 

 ing modifications of animal life as well." 



The above quotation from "The 

 Adventure of Life," by Dr. Robert W. 

 MacKenna, represents a mistaken as- 

 sumption in regard to heredity that is 

 very frequently encountered even in 

 text-books on eugenics. It is an es- 

 tablished generalization that the role 

 played by environment in producing 

 wide modifications compatible with life 

 is far greater in plant life than in animal, 

 and far greater on the simpler animal 

 tissues than on the more complex.^ 



' See Popcnnc and Johnson, "Applied Eugenics," p. 3. New York, 1918. 



