THE SELECTIVE FUNCTION OF RELIGION 361 
deterioration of its breed.” Weak, timid and sequacious people 
are not apt to be singled out for championing an unpopular cause, 
or for defending what is considered a dangerous heresy. As 
Lapouge remarks, ‘the persecuted are the superiors of their 
persecutors’’; they are apt to be the bold spirits who are willing to 
brave personal danger for what they deem to be the truth. And 
any country in which persecution has been vigorously carried on 
for a long period of years cannot fail to lose a large proportion of 
its best inheritance. 
Another dysgenic effect of religious selection is occasioned 
by the celibacy of the clergy, which has grown up especially in the 
Catholic church. Whatever may be said of the eugenic worth of 
the women who take the veil, the men who become priests or 
monks are above the average level of intellect. De Candolle in 
his Histoire des sciences et des savants has cited a long list of 
eminent men who were sons of Protestant clergymen and who 
would not have been born had the institution of celibacy pre- 
vailed in the Protestant churches. Of the ror scientists who were 
foreign members of the Academy of Sciences of Paris, 14, or over 
13 per cent, were the sons of pastors. As Lapouge has pointed 
out, a large proportion of eminent Jews are the sons of rabbis. 
For a long time the church afforded one of the most promising 
careers for men of exceptional intellect and character. To the 
extent to which such men were committed to a celibate life, the 
race suffered a loss of a valuable inheritance. Since the popula- 
tion of the Catholic world has sustained this loss for many cen- 
turies the cumulative effect of such a dysgenic process could 
scarcely fail to be considerable. 
An effect of religion more widespread than the one just dis- 
cussed is the tendency of the adherents of a particular cult to 
marry only within the limits of their own fold. Thus arises what 
Mr. Gulick would designate a form of “segregate breeding” 
whose effect is analogous to that of geographical isolation. Any 
isolated group tends, through continuous inbreeding, to become 
more and more nearly homozygous in successive generations. 
For this reason and perhaps others also, groups of a given species 
