238 
THE DESCENT OF MAN. 
Pakt I- 
Extinction follows chiefly from the competition of 
tribe with tribe, and race with race. Various checks 
are always in action, as specified in a former chapter, 
which serve to keep down the numbers of each savage 
tribe, — such as periodical famines, the wandering of 
the parents and the consequent deaths of infants, pro- 
longed suckling, the stealing of women, wars, accidents, 
sickness, licentiousness, especially infanticide, and, 
perhaps, lessened fertility from less nutritious food, and 
many hardships. If from any cause any one of these 
checks is lessened, even in a slight degree, the tribe 
thus favoured will tend to increase; and when one 
of two adjoining tribes becomes more numerous and 
powerful than the other, the contest is soon settled by 
war, slaughter, cannibalism, slavery, and absorption- 
Even when a weaker tribe is not thus abruptly swept 
away, if it once begins to decrease, it generally goes on 
decreasing until it is extinct . 31 
When civilised nations come into contact with bar- 
barians the struggle is short, except where a deadly cli- 
mate gives its aid to the native race. Of the causes which 
lead to the victory of civilised nations, some are plain 
and some very obscure. We can see that the cultivation 
of the land will be fatal in many ways to savages, fo r 
they cannot, or will not, change their habits. Xe'V 
diseases and vices are highly destructive ; and it appears 
that in every nation a new disease causes much death, 
until those who are most susceptible to its destructive 
influence are gradually weeded out ; 52 and so it may be 
with the evil effects from spirituous liquors, as well as 
with the unconquerably strong taste for them shewn by 
so many savages. It further appears, mysterious as is 
” Gerland (ibid. s. 12) gives facts in support of this statement. 
See remarks to this effect in Sir H. Holland’s ‘ Medical Notes and 
Reflections, ’ 1839, p. 390. 
