he year 1837 or 1838, convinced that species were mutable
productions, I could not avoid the belief that man must come under
the same law. Accordingly I collected notes on the subject for my own
satisfaction, and not for a long time with any intention of publishing.
Although in the 'Origin of Species' the derivation of any particular
species is never discussed, yet I thought it best, in order that no
honourable man should accuse me of concealing my views, to add that by
the work "light would be thrown on the origin of man and his history."
It would have been useless and injurious to the success of the book to
have paraded, without giving any evidence, my conviction with respect to
his origin.

But when I found that many naturalists fully accepted the doctrine of
the evolution of species, it seemed to me advisable to work up such
notes as I possessed, and to publish a special treatise on the origin of
man. I was the more glad to do so, as it gave me an opportunity of
fully discussing sexual selection--a subject which had always greatly
interested me. This subject, and that of the variation of our
domestic productions, together with the causes and laws of variation,
inheritance, and the intercrossing of plants, are the sole subjects
which I have been able to write about in full, so as to use all the
materials which I have collected. The 'Descent of Man' took me three
years to write, but then as usual some of this time was lost by ill
health, and some was consumed by preparing new editions and other minor
works. A second and largely corrected edition of the 'Descent' appeared
in 1874.

My book on the 'Expression of the Emotions in Men and Animals' was
published in the autumn of 1872. I had intended to give only a chapter
on the subject in the 'Descent of Man,' but as soon as I began to put my
notes together, I saw that it would require a separate treatise.

My first child was born on December 27th, 1839, and I at once commenced
to make notes on the first dawn of the various expressions which he
exhibited, for I felt convinced, even at this early period, that the
most complex and fine shades of expression must all have had a gradual
and natural origin. During the summer of the following year, 1840,
I read Sir C. Bell's admirable work on expression, and this greatly
increased the interest which I felt in the subject, though I could not
at all agree with his belief that various muscles had been specially
created for the sa