ich good inheritance is
effective, and this may be conveniently done by a study of the lives of
a group of people who inherited exceptionally strong physical
constitutions.

The people referred to are taken from a collection of histories of long
life made by the Genealogical Record Office of Washington.[189] One
hundred individuals were picked out at random, each of whom had died at
the age of 90 or more, and with the record of each individual were
placed those of all his brothers and sisters. Any family was rejected in
which there was a record of wholly accidental death (e.g., families of
which a member had been killed in the Civil War). The 100 families, or
more correctly fraternities or sibships, were classified by the number
of children per fraternity, as follows:

Number of Total number
Number of children per of children
fraternities fraternity in group

1 2 2
11 3 33
8 4 32
17 5 85
13 6 78
14 7 98
9 8 72
11 9 99
10 10 100
3 11 33
2 12 24
1 13 13
--- ---
100 669

The average at death of these 669 persons was 64.7 years. The child
mortality (first 4 years of life) was 7.5% of the total mortality, 69
families showing no deaths of that kind. The group is as a whole,
therefore, long-lived.

The problem was to measure the resemblance between brothers and sisters
in respect of longevity,--to find whether knowledge of the age at which
one died would justify a prediction as to the age at death of the
others,--or technically, it was to measure the fraternal correlation of
longevity. A zero coefficient here would show