group holds that cousin marriages in themselves, especially if not
carried through too many generations, are not harmful, but that if any
hereditary tendency to malformation or disease exists in the family of
the parents, this tendency, inherited through both parents is strongly
intensified in the offspring, and that consequently an increased
percentage of the offspring of cousin marriage may be afflicted with
hereditary diseases. This group includes a number of the later writers
such as Feer and Mayet. Among the earlier discussions, those of Dally
in France and George H. Darwin in England take substantially this
position. On the whole this theory seems to be the most reasonable one
and with a few modifications it will be seen to account for all the
facts herein presented.

It is undeniable that degeneracy does in some cases follow from the
marriage of near kin, and probably with greater frequency than from
non-related marriages. But it is likewise true that many of the
world's greatest men have been the products of close inbreeding,
sometimes continued through several generations. Frederick the Great
of Prussia was the product of three successive cousin marriages
between descendants of William the Silent,[42] and among his seven
brothers and sisters at least three others ranked among the ablest men
and women of the generation. Cousin marriage has always been frequent
in the "first families of Virginia" which have produced a phenomenal
percentage of able men. In fact, few persons who have traced their
pedigrees back through a number of generations, do not find some names
duplicated, as a result of cousin marriage.

[Footnote 42: Woods, _Heredity in Royalty_, pp. 74-75. The Great
Elector, a great-grandson of William the Silent, married his 1-1/2
cousin, a granddaughter of William and also a great-granddaughter of