82 MAN THE ANIMAL 



miserable is a peculiarly human trait). But the great point is 

 that while all these dreadful things have always existed, serious 

 concern and excitement about them has, on the whole, grown 

 just in proportion as the numbers of men — the sizes of popula- 

 tions — have increased. So then we shall devote this lecture 

 to some consideration of the numbers of men — human popu- 

 lations as they exist today, how they got that way, and the im- 

 plications they may have for human biology generally. 



A recent analysis (Pearl, The Natural History of Population, 

 1938), has led to certain broad results and principles that seem 

 to throw light on the general biology of population considered 

 dynamically. Perhaps we may start with a brief statement of 

 these results. In the nature of the case the statement will have 

 to be categorical, because there is not time to present the de- 

 tailed evidence. I regret that this is so. But I think the material 

 painstakingly gathered together may fairly be said to have 

 made the following general relations clear. 



1. The major problems of population are primarily and 

 fundamentally biological in nature, because the size and other 

 characteristics of populations rest upon the operation of the 

 basic biological principles of individual survival, reproduction, 

 variability, and their mutual interactions and integrations with 

 the environment. 



2. The state of any particular population at any particular 

 moment depends primarily upon and is determined by the 

 manner in which the specific biological elements that influence 

 fertility have been, and are, acting, in the direction either of its 

 promotion or its restriction. 



3. There is great variation among individuals and groups in 

 the biological elements that influence fertility, such as fre- 

 quency of coitus in wedlock, age at m.enarche and at menopause, 

 and other similar physiological and behavioral matters. 



4. The basic biological pattern of human reproductivity is 

 inherently and intrinsically different in a number of important 

 respects from that of other mammals and animals lower in the 

 evolutionary scale, and has been rendered still more widely 

 divergent by artificial alterations that man has consciously and 



