298 THE EEGULATION OF NUMBERS 



aside the idea of an optimum mimber, we must regard the popula- 

 tion, which any area is capable of supporting, as strictly limited. 

 Given the vast power of increase that we know always to be 

 present, there cannot commonly be a condition of under-popula- 

 tion — a condition, that is to say, in which population has ceased 

 to increase before it was checked by the food limit. For we are 

 not dealing with the spread of population into unoccupied areas ; 

 that occurred perhaps before there was any social organization. 

 We are dealing with a period in which all portions of the earth's 

 surface, relative to the degree of skill attained, had long been 

 fully occupied. Though increase of skill may at times enable 

 regions previously quite infertile to be occupied, this is altogether 

 an exceptional case ; increase of skill normally merely allows of 

 an increase of density in the same area. General considerations 

 point to the normal condition being of necessity either one in 

 which population has increased up to the level of subsistence or 

 one in which it has increased to the optimum level, and the 

 evidence presented shows that as a rule some approximation 

 to the latter condition is attained. General considerations on 

 the one hand and the evidence on the other both render wholly 

 unacceptable the idea that commonly there is a condition of 

 under-population which is followed by migration when the 

 pressure due to the catching up of the amount of food available 

 by the increase of population begins to be felt. Further, no support 

 is given to this view by the facts known regarding any particular 

 migration. What evidence is there, with regard to the Greek 

 migrations referred to by Professor Myres, that for some unknown 

 length of time, for some unknown reason, the increase of population 

 had not reached the limit made possible by the food-supply ? 

 Unless there is definite evidence of peculiar circumstances in some 

 peculiar combination, such a theory cannot be held to account for 

 migration. The idea of population catching up the means of 

 subsistence and bringing about a crisis followed by migration 

 is the product of an altogether unhistorical view of the matter.^ 

 We do know, indeed, that at times a condition of under-popula- 

 tion arises chiefly owing to the irregular action of certain factors 



* These remarks also apply to those cases in which countries at times appear to 

 be empty. Attention is, for example, sometimes drawn to the fact that England 

 appears to have been an ' empty ' country in the Middle Ages. The emptiness is 

 only apparent. Relative to the available skill and all other relevant circumstances 

 England was fully populated in the Middle Ages ; the tendency was rather towards 

 over- than under-population. 



