degenerate. Until the antecedents of a community are known it is of
course impossible to estimate the effect of consanguinity. The
exceptionally high percentage of deaf-mutism on Martha's Vineyard may
to some extent be due to a high percentage of consanguineous marriage,
but that inbreeding is not the primary cause is revealed by the
records showing that among the first settlers were two deaf-mutes,
whose defect has been inherited from generation to generation for two
hundred and fifty years.[13]

[Footnote 13: See article in Cincinnati _Gazette_, Jan. 22, 1895.]




CHAPTER II

RATIO OF THE CONSANGUINEOUS TO ALL MARRIAGES


Towards determining the average frequency of occurrence of
consanguineous marriages, or the proportion which such marriages bear
to the whole number of marriages, little has as yet been done in this
country. Professor Richmond Mayo-Smith estimated that marriages
between near kin constituted less than one per cent of the total,[14]
and Dr. Lee W. Dean estimates that in Iowa they comprise only about
one half of one per cent.[15] But these estimates are little more than
guesses, without any statistical basis.

[Footnote 14: _Statistics and Sociology_, p. 112.]