The Descent of Man

force whence the sick are drawn, have dark and
light-coloured hair, and hair of intermediate or
doubtful tints; and if a similar account were
kept by the same medical gentlemen, of all the
men who suffered from malarious and yellow
fevers, or from dysentery, it would soon be
apparent, after some thousand cases had been
tabulated, whether there exists any relation
between the colour of the hair and constitutional
liability to tropical diseases. Perhaps no
such relation would be discovered, but the investigation
is well worth making. In case any
positive result were obtained, it might be of
some practical use in selecting men for any particular
service. Theoretically the result would
be of high interest, as indicating one means by
which a race of men inhabiting from a remote
period an unhealthy tropical climate, might
have become dark-coloured by the better preservation
of dark-haired or dark-complexioned
individuals during a long succession of generations."),
to ascertain how far it holds good. The