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Show 106 THE DESCENT OF MAN. PART I. conscious and Teflect on its own existence? 'V e cannot answer; nor can we answer in regard to the ascending organic scale. The half-art and half-instinct of language still bears the stamp of its gradual evolution. The ennobling belief in God is not universal with man; and the belief in active spiritual agencies naturally follows from his other mental powers. The moral sense perhaps affords the best and highest distinction between man and the lower animals; but I need not say anything on this head, as I have so lately endeavoured to shew that the social instincts,-the prime principle of man's moral constitution 39-with the aid of active intellectual powers and the effects of habit, natura~ly lead to the golden rule, " As ye would that men should " do to you, do ye to them likewise;" and this lies at the foundation of morality. In a future chapter I shall make some few remarks on the probable steps and means by which the several mental and moral faculties of man have been gradually evolved. That this at least is possible ought not to be denied, when we daily see their development in erery infant; and when we may trace a perfect gradation from the mind of an utter idiot, lower than that of the lowest animal, to the mind of a Newton. 30 'The Thoughts of Marcus Aurelius,' &c., p. 13!>. CHAP. IY. MANNER OF DEVELOPI\-1ENT. CHAPTER IV. ON THE MANXER OF DEVELOPMENT OF MAN FROM SOME LOWER FoRM. ·; 107 Variability of body and mind in man-Inheritance-Causes of variability-Laws of variation the same in man as in the lower animals- Direct action of the conditions of life- Effects of the increased nse and disuse of parts- Arrested development- Reversion- Correlated variation- Rate of increase- Checks to increase-Natural selection- Man the most dominant animal in the world- Importance of his corporeal structure- The causes which have led to his becoming erect-Consequent changes of structure- Decrease in size of the canine teeth- Increased size and altered shape of the skull-Nakedness- Absence of a tail- Defenceless condition of man. vVE have seen in the first chapter that the homological structure of man, his embryological development and the rudiments which he still retains, all declare in the plainest manner that he is descended from some lower form. The possession of exalted mental powers is no insuperable objection to this conclusion. In order that an ape-like creature should have been transformed into man, it is necessary that this early form, as well as many successive links, should all have varied in mind and body. It is impossible to obtain direct evidence on this head · but if it can be shewn that man now varies -that hi~ variations are induced by the same general causes, and obey the same general laws, as in the case of the lower animals-there can be little doubt that the preceding intermediate links varied in a like manner. The variations at each successive stage of descent must, also, have been in some manner accumulated and fixed. |