The Descent of Man

produce twins runs in families. (59. Mr. Sedgwick,
'British and Foreign Medico-Chirurgical
Review,' July 1863, p. 170.)
Notwithstanding that savages appear to be less
prolific than civilised people, they would no
doubt rapidly increase if their numbers were
not by some means rigidly kept down. The Santali,
or hill-tribes of India, have recently afforded
a good illustration of this fact; for, as
shewn by Mr. Hunter (60. 'The Annals of Rural
Bengal,' by W.W. Hunter, 1868, p. 259.), they
have increased at an extraordinary rate since
vaccination has been introduced, other pestilences
mitigated, and war sternly repressed.
This increase, however, would not have been
possible had not these rude people spread into
the adjoining districts, and worked for hire.
Savages almost always marry; yet there is some
prudential restraint, for they do not commonly
marry at the earliest possible age. The young
men are often required to shew that they can