THE REGULATION OF NUMBERS AMONG HISTORICAL RACES 270
(1) Among these races, in spite of certain complications, the
principle of the optimum number holds good. (2) The evidence for
the first sub-group is too scanty to base conclusions upon. (3)
Among the races of the second sub-group we see how the pressure
is felt, and (4) we have knowledge of the factors at work, but
(5) in India, China, and Egypt there is evidence that the
factors are not effective, and that over-population occurs. (6)
In the third sub-group, where the factors are different, (7) we
can see in disabilities placed upon serfs, and (8) in
difficulties, (9) restrictions, and (10) Poor Law provisions
hindrances to marriage. (11) The system was generally effective,
though over-population occasionally occurred. (12) In the fourth
sub-group there is no evidence of over-population; (13) the
factors are rather different, and (14) pressure comes about by
unconscious response to economic conditions. (15) Summarizing
the position for all groups we find that owing to the great
power of increase, customs restrictive of increase are always
necessary, and (16) have taken various forms (17) with varying
effectiveness. (18) Changes in quantity are a result rather than
a primary cause of historical events. (19) Neither migration
(20) nor war is due directly to over-population, though the
position as regards quantity may be an element in the situation
predisposing nations towards migration and war.