The Descent of Man

The fewness and the comparative simplicity of
the instincts in the higher animals are remarkable
in contrast with those of the lower animals.
Cuvier maintained that instinct and intelligence
stand in an inverse ratio to each other; and some
have thought that the intellectual faculties
of the higher animals have been gradually developed
from their instincts. But Pouchet, in an
interesting essay (2. 'L'Instinct chez les Insectes,'
'Revue des Deux Mondes,' Feb. 1870, p.
690.), has shewn that no such inverse ratio really
exists. Those insects which possess the most
wonderful instincts are certainly the most intelligent.
In the vertebrate series, the least intelligent
members, namely fishes and amphibians,
do not possess complex instincts; and amongst
mammals the animal most remarkable for its
instincts, namely the beaver, is highly intelligent,
as will be admitted by every one who has
read Mr. Morgan's excellent work. (3. 'The
American Beaver and His Works,' 1868.)