BIOLOGICAL FOUNDATIONS 17 



simple cell or cells, all higher and more complex forms of 

 life slowly evolved. 



And now let us consider the Method of Evolution. 

 Evolution works by '' Natural Selection:* There are 

 two factors in Natural Selection, Heredity and Varia- 

 tion, By Heredity we mean that the offspring is like 

 the parent. By Variation we mean that the offspring 

 is not exactly like the parent, 



I cannot gbjt you a better illustration of Heredity than 

 the fact that human infants are born of human parents. 

 But though a child takes after father, or mother, as the 

 case may be, it is not exactly like either father or mother ; 

 nor is it exactly a cross between the two. The child 

 has an individuality of its own, and that individuality 

 is Variation, Now the Law of Natural Selection, or, 

 as it was named by Herbert Spencer, the *' Law of the 

 Survival of the Fittest;* says, that any variation that is 

 favourable to the organism will help the organism to 

 survive, so that this Variation is likely to be handed on 

 by Heredity to the next generation ; whilst any Variation 

 which is unfavourable to the organism, will tend to 

 prevent its Survival, so that this Variation is less likely 

 to be handed on by Heredity to the next generation. 

 Let us take an extreme example of an unfavourable 

 Variation, and consider the case of a child born with 

 hare-lip and cleft palate. This hideous deformity 

 prevents the child sucking, and therefore it will be very 

 difficult to rear. It is exceedingly unlikely that such a 

 child will ever have children to whom the deformity 

 would be handed on. On the other hand, favourable 

 variations in the direction of health, strength, beauty and 

 intelligence, will help the child to survive, so that these 

 variations are much more likely to be handed on by 

 Heredity to the next generation, 



Darwin himself never discussed the ethics of Natural 

 Selection, but popular imagination saw nothing in his 



