The Descent of Man

Differences of this kind between the highest
men of the highest races and the lowest savages,
are connected by the finest gradations.
Therefore it is possible that they might pass
and be developed into each other.
My object in this chapter is to shew that there is
no fundamental difference between man and
the higher mammals in their mental faculties.
Each division of the subject might have been
extended into a separate essay, but must here
be treated briefly. As no classification of the
mental powers has been universally accepted, I
shall arrange my remarks in the order most
convenient for my purpose; and will select those
facts which have struck me most, with the
hope that they may produce some effect on the
reader.
With respect to animals very low in the scale, I
shall give some additional facts under Sexual
Selection, shewing that their mental powers are
much higher than might have been expected.