DAEWINISM, BIOMETRY AND SOME 
RECENT BIOLOGY. L 
By KARL PEARSON, F.R.S. 
(1) The principle of the "survival of the fitter" as the basis of progressive 
evolution depends upon the co-existence of three factors, (i) the destruction, or 
elimination as far as reproduction is concerned, of those less fitted to their environ- 
ment, (ii) the inheritance of the somatic characters on which the fitness depends, 
and (iii) the absence of any differential fertility. These essential principles of 
natural selection are frequently overlooked not only by sociologists but by biologists, 
and whenever they are disregarded, there an inroad of a serious nature has been 
made into the Darwinian theory of evolution. It is possible to illustrate this point 
in a variety of ways. Thus Nature in the struggle for existence in wild life, regards 
and can regard only somatic characters. A somatic character Avhich is not inherited 
in a greater or lesser degree has no value in the Darwinian theory of evolution. 
Again, a genetic constitution which does not manifest itself in somatic characters, 
i.e. is not directly or indirectly correlated with some one or other somatic character, 
cannot form the subject of Darwinian evolution. To what extent are patent 
qualities inherited ? This must always be the fundamental problem of any 
Darwinian interpretation of living forms. And — above all in populations where 
selective mating is small — this problem must and will remain in the first place 
a statistical problem. The knowledge of an universal physiological law of heredity 
would immensely aid artificial breeding ; it would essentially aid civilized man in 
the generations to come, when his knowledge dictates and controls his emotional 
needs*. But from the pure standpoint of Darwinian evolution, the fundamental 
problem remains the intensity of the transmission of somatic characters in the 
* There is not the least doubt that good physique generally and that mental capacity in many 
cases, can in the present state of human development have sexual attraction ; deformity and imbecility 
produce sexual repulsion. With greater and more widely spread knowledge of genetics, the gametic 
constitution of an individual as roughly manifested in the average somatic characters of other members 
of the stock may well come to be a potent emotion-controlling factor of a practically unconscious kind. 
Even to-day many human beings would, as far as matters of sex are concerned, experience revulsion 
rather than attraction from an individual whose relatives were physically, mentally or socially defec- 
tive. There is no doubt that this emotional state will be emphasised the more we are trained from 
childhood to give the proper relative weights to environment and heredity. 
