September i, 1914] 



SCIENCE 



327 



the majority of these infants were to sur- 

 vive. The decline in the birth-rate in 

 countries already over-populated is often 

 deplored, and we are told that a nation in 

 which population is not rapidly increasing 

 must be in a decline. The slightest ac- 

 quaintance with biology, or even school- 

 boy natural history, shows that this infer- 

 ence may be entirely wrong, and that 

 before such a question can be decided in 

 one way or the other, hosts of considera- 

 tions must be taken into account. In nor- 

 mal stable conditions population is station- 

 ary. The laity never appreciates, what is 

 so clear to a biologist, that the last century 

 and a quarter, corresponding with the great 

 rise in population, has been an altogether 

 exceptional period. To our species this 

 period has been what its early years in 

 Australia were to the rabbit. The exploita- 

 tion of energy-capital of the earth in coal, 

 development of the new countries, and the 

 consequent pouring of food into Europe, 

 the application of antiseptics, these are the 

 things that have enabled the human popu- 

 lation to increase. I do not doubt that if 

 population were more evenly spread over 

 the earth it might increase very much 

 more; but the essential fact is that under 

 any stable conditions a limit must be 

 reached. A pair of wrens will bring off a 

 dozen young every year, but each year you 

 will find the same number of pairs in your 

 garden. In England the limit beyond 

 which under present conditions of distri- 

 bution increase of population is a source 

 of suffering rather than of happiness has 

 been reached already. Younger commu- 

 nities living in territories largely vacant 

 are very probably right in desiring and 

 encouraging more population. Increase 

 may, for some temporary reason, be essen- 

 tial to their prosperity. But those who 

 live, affl do, among thousands of creatures 

 in a state of semi-starvation will realize 



that too few is better than too many, and 

 will acknowledge the wisdom of Beclesi- 

 asticus, who said, "Desire not a multitude 

 of unprofitable children." 



But at least it is often urged that the 

 decline in the birth-rate of the intelligent 

 and successful sections of the population — 

 I am speaking of the older communities — 

 is to be regretted. Even this can not be 

 granted without qualification. As the 

 biologist knows, differentiation is indispen- 

 sable to progress. If population were 

 homogeneous civilization would stop. In 

 every army the officers must be compara- 

 tively few. Consequently, if the upper 

 strata of the community produce more 

 children than will recruit their numbers 

 some must fall into the lower strata and 

 increase the pressure there. Statisticians 

 tell us that an average of four children 

 under present conditions is sufficient to 

 keep the number constant, and as the ex- 

 pectation of life is steadily improving we 

 may perhaps contemplate some diminution 

 of that number without alarm. 



In the study of history biological treat- 

 ment is only beginning to be applied. For 

 us the causes of the success and failure of 

 races are physiological events, and the 

 progress of man has depended upon a 

 chain of these events, like those which have 

 resulted in the "improvement" of the 

 domesticated animals and plants. It is 

 obvious, for example, that had the cereals 

 never been domesticated cities could 

 scarcely have existed. But we may go 

 further, and say that in temperate coun- 

 tries of the Old World (having neither rice 

 nor maize) populations concentrated in 

 large cities have been made possible by the 

 appearance of a "thrashable" wheat. The 

 ears of the wild wheats break easily to 

 pieces, and the grain remains in the thick 

 husk. Such wheat can be used for food, 

 but not readily. Ages before written his- 



