2o6 evolution: the ages and tomorrow 



sterile environment of the rural-or urban-Tobacco Road, the 

 Newton and the half-wit may seem like brothers. But in the en- 

 vironment which affords adequate 'royal jelly,' the Newton uses 

 a falling apple to discover the force that holds the planets in their 

 courses. To the half-wit, an apple can be no more than a tasty 

 morsel, and the stars are holes in the sky, with never a link between 

 them.* 



Modern methods of measuring intelligence began with 

 the French psychologist Alfred Binet and his concept of 

 "mental age." Modification and improvements of the Binet 

 test and the establishment of the intelligence quotient (I.Q.) 

 concept gives us a method which now, in the hands of com- 

 petent technicians, can determine with sufficient accuracy 

 the mental level of the individual and of a population. The 

 I.Q. is a comparison of actual age with mental age on a scale 

 of to 200. If the actual age of a child is 12 and the mental 

 age is 12, the I.Q. is 100, or average. If a child has an actual 

 age of 10 years but tests only 7 years old mentally the I.Q. 

 would be 70; in other words, the child shows only 70 per 

 cent of the mental growth that might be expected of it. In 

 this case the child would be rated inferior. A child of 8 years 

 actual age giving a test score of about 10 Yj years mental 

 age would have an I.Q. of 130 and be rated superior. 



How these differences in innate capacity to learn (I.Q.) 

 are distributed in present-day populations is of high im- 

 portance in the evolution of man's future societies. In the 

 early formative years of man's rise from ape-like ancestors, 

 natural selection was no doubt "working over" the genetic 

 variations which were controlling the level of intelligence. 

 The individual with variations toward greater alertness and 

 intelligence had a better chance to survive and reproduce. 

 Unfavorable variations tending to produce dull and unin- 

 telligent individuals were prevented from accumulating in 

 the population's "gene pool" since individuals with unde- 



* R. C. Cook, Human Fertility, The Modern Dilemma (New York: 

 William Sloane Associates, 1951), pp. 274-75. 



