XII. THE EVOLUTION OF MANKIND AND ITS FUTURE 437 



diminution in the requirement of nervous strain of animality, con- 

 tributing to the more extensive production of growth hormone. 



In .this way, causes becoming results, results becoming causes, the 

 speed of the orthogenetic progress of man towards gigantism will be 

 increased acceleratively. 



As described above, the average increase in height in a generation 

 of Yale University students has been reported to be about 1 V2 inches. 

 Swedish stature has increased 9 cm in the last hundred years (104). 

 If man will continue to become bigger at this rate, after 10,000 years 

 he will be a giant over 40 feet. On the other hand, as the body 

 weight is directly proportional to the square of height, animals becom- 

 ing bigger over a certain extent would fail to resist the terrestrial 

 gravitation, thus there being no choice but to become extinct. The 

 whale can exist notwithstanding its gigantic size owing to its aquatic 

 life as water alleviates the gravitation. 



However, more dreadful foresight may arise from the point that 

 man is losing rapidly the structural rigidity in the genes. The fright- 

 ful speed of specialization may be dependent upon this point, which 

 seems to be accelerated by the growth hormone ; at the same time, 

 this loss of rigidity in genes may give rise to an extremely changeable 

 character of protoplasm with profound and incessant production of 

 various malevolent viruses including cancers. Thus mankind is bound 

 to become extinct in a near future as did the gigantic reptiles. 



As is well known, a great many reptilian orders, including those 

 containing the dinosaurs and pterydactyls, are entirely extinct, but 

 still at present a number of small reptiles are existing. In like man- 

 ner, some of the mankind may be left behind on the earth even when 

 the majority of them will be extinct, and presumably those who are 

 to be left are the people who are living in a climate lacking in the 

 stimulating factor and who are compelled to live in "a nutritious 

 deficiency with a nervous tenseness of animality on account of their 

 uncivilized life, which must always be associated with the climate. 



Irritability and uneasiness as well as the want of food peculiar to 

 uncivilized life may result in the precocious sexual maturity through 

 the hormonal pattern induced by the situation, presumably involving 

 the hyperfunction of thyroid and gonadal glands, and this may cause 

 the uncivilized, small people to have many children, in contrast to 

 civilized, specialized people. This seems to be a phenomenon common 

 to the animal kingdom in general. The smaller the animal, the more 

 numerous enemies it must have, and accordingly the more nerv^ous 

 tenseness must be required, and again therefore the peculiar hormonal 

 pattern mainly concerned with thyroid and gonadal function should be 

 developed the more. Thus the smaller the animal, generally the more 



