398 The Journal 
found long ago by biometricians,* that 
elder children tend to live longer than 
younger ones. The investigation in 
question did not deal directly with the 
first-born, but is obviously parallel to a 
certain extent. 
Dealing with a thousand or more 
pairs, Miss Beeton and Pearson then 
found the following average ages at 
death: 
Elder Younger 
All adult adult adult 
PSTD. acts k hee ee 57.795 59.924 55.667 
BroOnner... «260s 56.568 58.560 54.575 
Here an elder brother or sister was 
one who might have been born one 
year or twenty before the younger 
brother or sister. For both sexes, it 
seems that the elder lived about four 
years longer than the younger. 
The result appeared so interesting to 
them that they secured 1,051 pairs of 
brothers and 733 pairs of sisters where 
the interval between births was known, 
and further studied them. ‘The data,” 
says Prof. Pearson, ‘‘are not quite the 
same as for our pairs of adult brothers 
and sisters given above, but they show 
much the same advantage, 1.e., four 
years to the elder. They further dem- 
onstrate that longevity is correlated 
with position in the family.’ This fact 
is suggestive for the source of other 
variations in the characters of an array 
of brethren. It may be that variability 
within the array is not purely random, 
but correlated like variability in lon- 
gevity, with birth order. Our numbers 
show that on the whole the earlier-born 
members of a family are the stronger, 
or at any rate fitted to survive the 
longer.”’ 
It was possible from the data to 
work out interesting formulae for pre- 
6 Beeton and Pearson, ubt supra. 
7 The facts as given by Beeton and Pearson, p. 
Mean excess in life of elder.............-.00055 
TOLER CCSS 5 halo Asc Arca See ehee Co, Ca 
Mean interval between births................. 
Mo Fab ay tories CORAM oe” ot ATA! fp (RED 
of Heredity 
dicting the probable excess of life (e) of 
an elder brother or sister from a knowl- 
edge of the birth interval (7), both 
being taken in years: 
Elder brother e 7 
Elder sister e 8 
“Thus a brother born ten years 
before another brother has probably 
seven years greater duration of life; a 
sister born ten years before another 
sister has probably about six years 
greater duration of life.” It is hardly 
necessary to add that these formulae 
will rarely hold good in individual 
cases, but apply only when a large 
population is dealt with. 
While these Beeton-Pearson data may 
appear to conflict in some ways with 
the Genealogical Record Office data 
which I have compiled, it must be 
pointed out that they are not directly 
comparable. The former were taken 
from pedigrees kept by the Society of 
Friends in England, while the latter are 
isolated cases picked out of a very 
heterogeneous population, on the basis 
of a single fact—that an individual had 
reached advanced age. 
In conclusion, it has been shown that 
among the long-lived people in the 
United States, first-born are propor- 
tionately more numerous than any 
other children. It is suggested that 
this may be because they are (a) more 
variable in respect to longevity and (b) 
subjected to a more stringent selection 
at birth. Previous work showing that 
earlier-born children in a family live 
longer than later-born appears, as far 
as it goes, to corroborate the validity of 
the conclusion reached from a study of 
the Genealogical Record Office data. 
54, are: 
Brothers Sisters 
ee ktry Serer ire 4.289 yrs. 4.542 yrs. 
eT eR te 22.0053 yrs. 22.1325 yrs. 
RAG Ate seta ete 6.462 yrs. 6.7503 yrs. 
MY oo eC 4.3530 yrs. 4.6856 yrs. 
1062 + .0206 .1201 + .0246 
