Noteworthy Families (Modern Science) | Page 8

of the numbers of their
brothers and uncles; some few of these had, however, placed a query
here or there, or other sign of hesitation. As the number of completely
available returns scarcely exceeded 100, I have confined the following
tables to that number exactly, taking the best of the slightly doubtful

cases. It would have been possible, by utilizing partial returns and
making due allowances, to have obtained nearly half as many again, but
the gain in numbers did not seem likely to be compensated by the
somewhat inferior quality of the additional data.
The first three lines of Table V. show that there is no significant
difference between the average numbers of brothers and sisters, nor
between those of fathers' brothers and fathers' sisters, nor again
between those of mothers' brothers and mothers' sisters; nor is there any
large difference between those of male and female cousins, but it is
apparently a fact that the group of "brothers" is a trifle smaller than that
of uncles on either side. It seems, therefore, that the generation of the
Subjects contains a somewhat smaller number of individuals than that
of either of their Parents, being to that extent significant of a lessening
population so far as their class is concerned.
TABLE V.--NUMBER OF KINSFOLK IN ONE HUNDRED
FAMILIES WHO SURVIVED CHILDHOOD.
_________________________________________________________
_____________ | | | | | | | Generic | Specific | Number of | Specific |
Number of | | Kinships. | Kinships. | Persons. | Kinships. | Persons. |
|_______________|_______________|___________|______________|
___________| | | | | | | |Brothers and | bro | 206 | si | 207 | | sisters | | | | |
|_______________|_______________|___________|______________|
___________| | | | | | | |Uncles and | fa bro | 228 | fa si | 207 | | aunts | me
bro | 219 | me si | 238 |
|_______________|_______________|___________|______________|
___________| | | | | | | | | Mean | 224 | Mean | 223 |
|_______________|_______________|___________|______________|
___________| | | | | | | |First cousins, | fa bro son | 265 | fa bro da | 302 | |
male and | fa si son | 184 | fa si da | 208 | | female | me bro son | 236 | me
bro da | 266 | | | me si son | 237 | me si da | 246 |
|_______________|_______________|___________|______________|
___________|
It may seem at first sight surprising that a brother and a sister should
each have the same average number of brothers. It puzzled me until I

had thought the matter out, and when the results were published in
"Nature," it also seems to have puzzled an able mathematician, and
gave rise to some newspaper controversy, which need not be
recapitulated. The essence of the problem is that the sex of one child is
supposed to give no clue of any practical importance to that of any
other child in the same family. Therefore, if one child be selected out of
a family of brothers and sisters, the proportion of males to females in
those that remain will be, on the average, identical with that of males to
females in the population at large. It makes no difference whether the
selected child be a boy or a girl. Of course, if the conditions were
"given a family of three boys and three girls," each boy would have
only two brothers and three sisters, and each girl would have three
brothers and two sisters, but that is not the problem.
Subject to this explanation, the general accuracy of the observed figures
which attest the truth of the above conclusion cannot be gainsaid on
theoretical grounds, nor can the conclusions be ignored to which they
lead. They enable us to make calculations concerning the average
number of kinsfolk in each and every specified degree in a stationary
population, or, if desired, in one that increases or decreases at a
specified rate. It will here be supposed for convenience that the average
number of males and females are equal, but any other proportion may
be substituted. The calculations only regard its fertile members; they
show that every person has, on the average, about one male fertile
relative in each and every form of specific kinship.
Kinsfolk may be divided into direct ancestry, collaterals of all kinds,
and direct descendants. As regards the direct ancestry, each person has
one and only one ancestor in each specific degree, one fa, one fa fa, one
me fa, and so on, although in each generic degree it is otherwise; he has
two grandfathers, four great-grandfathers, etc. With collaterals and
descendants the average number of fertile relatives in each specified
degree must be stationary in a stationary population, and calculation
shows that number is approximately one. The calculation takes no
cognizance of infertile relatives, and