358 AN INTRODUCTION TO MODERN GENETICS 



Steps which are within the bounds of probability. When it is remem- 

 bered that we are still imcertain whether hereditary differences have 

 any part at all in causing the class differences in intelUgence, while it 

 cannot be denied that the environment has some hand in this, the 

 priority of environmental over genetical methods of raising the general 

 inteUigence becomes obvious. Moreover, the genetical methods involve 

 us in something of a vicious circle; the self-control and conscious fore- 

 thought required for eugenical progress is scarcely likely to appeal to a 

 comparatively imintelligent populace, and it is not until people have 

 attained a certain level of awareness, probably higher than that found 

 in the majority to-day, that we may expect them to advance through 

 their own eugenical efforts. Until the essential improvements in social 

 hygiene have been made, and society reaps the very great advantages 

 which can be confidently expected from such measures, proposals of 

 "positive" eugenics for improving the human stock remain only of 

 secondary importance. 



The methods used in animal breeding could theoretically be used to 

 improve mankind. In most cases, human customs and beliefs would 

 be profoundly outraged if this were attempted. Thus few people 

 would seriously urge a large-scale programme of selective mating or 

 inbreeding of superior stocks. Muller^ has pointed out that the technique 

 of artificial insemination may, in time, remove the psychological 

 objections which at present stand in the way of attempting "grading 

 up," which, it will be remembered (p. 311), involves the use of all 

 females but only selected sires. If men and women could be persuaded 

 that a husband and father need not be the biological sire of his children, 

 it would be possible to use only sperm from superior men, and to give 

 every individual at least a haploid set of superior chromosomes.^ Per- 

 haps, if social progress continues, man may be educated up to the 

 point of considering such possibilities seriously. Still further in the 

 future we may envisage a tissue culture technique of preserving the 

 gonads of highly superior men for perpetual use; and the artificial 

 production of polyploidy and polyploid hybrids cannot be dismissed as 

 fantastic, alarming though the prospect of such experiments may be. 

 ^ Muller 1935. 2 Brewer 1935, Huxley 1936. 



