that their mental faculties are of the utmost importance to animals in a state of nature.  Therefore the conditions are favorable for their development through natural selection.  The same conclusion may be extended to man; the intellect must have been all-important to him, even at a very remote period, as enabling him to invent and use language, to make weapons, tools, traps, etc., whereby, with the aid of his social habits, he long ago became the most dominant of all living creatures.”

It is further pointed out that a great stride in the development of man’s intellect must have followed as soon as the half-art and half-instinct of language came into use; for the continued use of language must have reacted on the brain, and produced an inherited effect, and this again will have reacted on the improvement of language.  The largeness of the brain in man relatively to his body, compared with the size of that organ in the lower animals, is attributable in chief part to the early use of some simple form of language, that engine which affixes signs to all sorts of objects and qualities, and excites trains of thought which would never arise from the mere impression of the senses, or, if they did arise, could not be followed out.  The higher intellectual powers of man, such as those of ratiocination, abstraction, self-consciousness, etc., probably follow from the continued improvement and exercise of the other mental faculties.

How man’s moral qualities came to be developed is an interesting problem which is considered by Darwin at some length.  He holds that their foundation lies in the social instincts under which term are included family ties.  These instincts are highly complex, and, in the case of the lower animals, give special tendencies toward certain definite actions.  But the more important elements are love and the distinct emotion of sympathy.  Animals endowed with the social instincts take pleasure in one another’s company, warn one another of danger, defend and aid one another in many ways.  These instincts do not extend to all the individuals of the species, but only to those of the same community.  As, however, they are highly beneficial to the species, they have in all probability been acquired through natural selection.  In Darwin’s judgment the moral nature of man has reached its present standard partly through the advancement of his reasoning powers, and consequently, of a just public opinion, but especially from his sympathies having been rendered more tender and widely diffused through the effects of habit, example, instruction, and reflection.  It is pronounced not improbable that, after long practice, virtuous tendencies may be inherited.