234 



LIFE ON THE EARTH 



tain fish in dark caves are blind. The lizards and 

 spiders of the famous Mammoth Cave are colorless. 

 Among honeybees an egg may develop into a worker 

 or a queen, depending upon the food the larva re- 

 ceives. Conditions of the environment also affect hu- 

 man beings. A lack of vitamins in food produces 

 deformities of the body and certain diseases. A lack 

 of iodine may retard physical and mental develop- 

 ment. By education and practice one may develop 

 habits and skills that are not found in an uneducated 

 person. Too much food makes many people fat. 



Why do you resemble your parents? Many traits 

 appear generation after generation in living things re- 

 gardless of a changing environment. Healthy cows 

 that produce a large quantity of milk are selected to 

 be mothers rather than cows that give only a small 

 quantity because they transmit this trait to their 

 offspring. For hatching purposes chicken raisers use 

 eggs from hens that lay over 200 eggs a year, for egg- 

 laying ability seems to be a hereditary trait. Differ- 

 ences are found among plants because they come from 

 different stocks. Some cotton plants produce short 

 fibers while others produce long fibers. Some corn 

 plants produce long ears of corn, others short ears ; 

 some corn plants produce white grains on the ear, 

 whereas others produce yellow or red grains, depend- 

 ing upon their particular variety. These traits may 

 appear generation after generation even though en- 

 vironment or outward conditions change. 



Heredity operates in man just as it does in other 

 animals and in plants. We commonly observe, and 

 hear people discuss, resemblances between parents 

 and their children and between brothers and sisters. 

 These common observations have been confirmed by 

 scientific studies. Certain selected human traits such 

 as color of hair and eyes, skin color, temperament, 

 and intelligence have been traced through many gen- 

 erations. Heredity operates according to law and 

 order. 



Who was Gregor Mendel and for what is he noted ? 

 Gregor Mendel, an Austrian monk, discovered in 1866 

 that heredity operates under very definite laws. The 

 principles of heredity that he discovered were for- 

 gotten until about 1900, when they were rediscovered 

 by several other investigators. Since 1900 many ex- 

 periments on heredity have been carried on, and it is 

 believed that all kinds of physical and mental traits 

 are transmitted from generation to generation. 



Two families are commonly cited as examples of 

 heredity. Jonathan Edwards, an eminent man, lived 

 in New England during colonial times. In the year 

 1900 records of 1,394 of his descendants were studied. 

 The tabulated facts that follow show the outstanding 

 achievements of this notable family. 



295 college graduates 

 13 college presidents 



ICO clergymen, missionaries, or theological profes- 

 sors 



100 lawyers 

 30 judges 

 80 public officials 

 65 college professors 

 60 physicians 



75 officers of army and navy 

 60 prominent authors 



Winship states that almost if not every department 

 of social progress and of public weal has felt the im- 

 pulse of this healthy, long-lived family. It is not 

 known that any of them was ever convicted of a crime. 

 A striking contrast to the Edwards family is fur- 

 nished by the Jukes family. Max Jukes, a lazy and de- 

 generate backwoodsman who lived in the state of New 

 York, was the founder of the Jukes family of defec- 

 tives, of which about twelve hundred descendants 

 have been traced. It includes: 

 310 professional paupers 

 300 deaths in infancy 

 400 physical wrecks from debauchery 

 60 habitual thieves 

 50 immoral women 

 7 murderers 

 130 other criminals 



At the time this record was made this family had al- 

 ready cost the state of New York $1,250,000. All this 

 crime, immorality, and expense to the state might 

 have been avoided if the original ancestor had been 

 prevented from producing offspring. 



Can mankind be improved? What a person is or 

 becomes is determined by the influences of three 

 great factors: (1) heredity or 

 the characteristics transmitted 

 to him by his ancestors, (2) 

 environment or his surround- 

 ings, and (3) training or what 

 he does. These three factors 

 may be represented in the 

 form of a triangle (see Fig. 

 372). Heredity is made the 

 base of the triangle because an 

 individual cannot change his 

 heredity. Environment and training, the two sides of 

 the triangle, may be modified with resulting changes 

 in the individual. 



In the United States today there are hundreds of 

 thousands of men and women with serious physical 

 and mental defects. Many of these defects are heredi- 

 tary. More than half of the cases of feeble-mindedness 

 are believed to be hereditary. Crime, immorality, pov- 



MEREDITY 



FIG. 372 



