The Sex-Ratio in Human Populations 
1901. It seems, therefore, that the progress of medical science 
has preserved the excess of males at birth well into adult life, 
but that by contrast, in middle and old age, it has done more 
for women than for men. 
110 


{00 mag OR aan nee EQUALITY 
© 1960 
A i901 
90 
80 
70 
MALES PER 100 FEMALES 
60 
50 
a a a a et 
9 ° 10 1S 20 25 30 35 40 45 SO 5S 60 65 70 7s 80 85+ 
4 9 14 19 24 29 34 39 44 49 54 59 64 69 74 79 84 
QUINQUENNIAL AGE GROUPS 
Fig. 2. Sex-ratio according to age (England and Wales). 
The sex-ratio among adults at successive stages of the life- 
cycle is, therefore, much affected by differential postnatal mor- 
tality. We must now ask whether the sex-ratio at birth is 
influenced by differential prenatal mortality and if so, whether 
this fact has any bearing on fluctuations in the sex-ratio at this 
time. Unfortunately, very little is known about the sex inci- 
dence of prenatal mortality or of the sex-ratio of living foetuses 
at various stages of pregnancy, either in man or animals, but 
some facts are available. Firstly, there was until quite recently 
a large excess of males among stillbirths. This fact may be taken 
oo 
