The Descent of Man

It seems at first sight a mysterious fact that in
different nations, under different conditions
and climates, in Naples, Prussia, Westphalia,
Holland, France, England and the United States,
the excess of male over female births is less
when they are illegitimate than when legitimate.
(54. Babbage, 'Edinburgh Journal of Science,'
1829, vol. i. p. 88; also p. 90, on still-born children.
On illegitimate children in England, see
'Report of Registrar-General for 1866,' p. xv.)
This has been explained by different writers in
many different ways, as from the mothers
being generally young, from the large proportion
of first pregnancies, etc. But we have seen
that male infants, from the large size of their
heads, suffer more than female infants during
parturition; and as the mothers of illegitimate
children must be more liable than other women
to undergo bad labours, from various causes,
such as attempts at concealment by tight lacing,
hard work, distress of mind, etc., their male
infants would proportionably suffer. And this