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170 NATURAL SELECTION ^ vintiesof" mankind approximated more closely than they do atthe present day. At the same time this is but negativeevidence. A condition of immobility for four or five thousandyears does not preclude an advance at an earlier epoch,and if we can show that there are causes in nature whichwould check any further physical change when certain conditionswere fulfilled does not even render such an advanceimprobable, if there are any general arguments to be adducedin its favour. Such a cause, I believe, does exist ;and Ishall now endeavour to point out its nature and its mode ofoperation.Outline of the Theory of Natural SelectionIn order to make my argument intelligible, it is necessaryfor me to explain very briefly the theory of natural selectionpromulgated by Mr. Darwin, and the power which itpossesses of modifying the forms of animals and plants. Thegrand feature in the multiplication of organic life is, thatclose general resemblance is combined with more or lessindividual variation. The child resembles its parents orancestors more or less closely in all its peculiarities, deformities,or beauties it resembles them in; general more than itdoes any other individuals ; yet children of the same parentsare not all alike, and it often happens that they differ veryconsiderably from their parents and from each other. Thisis equally true of man, of all animals, and of all plants.Moreover, it is found that individuals do not differ from theirparents in certain particulars only, while in all others theyare exact duplicates of them. Theydiffer from them andfrom each other in every particular in form, in : size, incolour ;in the structure of internal as well as of externalorgans in those;subtle peculiarities which produce differencesof constitution, as well as in those still more subtle oneswhich lead to modifications of mind and character. In otherwords, in every possible way, in every organ, and in everyfunction, individuals of the same stock vary.Now, health, strength, and long life are the results of aharmony between the individual and the universe that surroundsit. Let us suppose that at any given moment thisharmony is perfect. A certain animal is exactly fitted to

vin THE DEVELOPMENT OF HUMAN RACES 171secure its prey, to escape from its enemies, to resist theinclemencies of the seasons, and to rear a numerous andhealthy offspring. But a change now takes place. A seriesof cold winters, for instance, come on, making food scarce,and bringing an immigration of some other animals to competewith the former inhabitants of the district. The newimmigrant is swift of foot, and surpasses its rivals in thepursuit of game the winter; nights are colder, and require athicker fur as a protection, and more nourishing food to keepup the heat of the system. Our supposed perfect animal isno longer in harmony with its universe it is in ;danger ofdying of cold or of starvation. But the animal varies in itsoffspring. Some of these are swifter than others they stillmanage to catch food enough some are hardier;and morethickly furred they manage in the cold nights to keep warmenough the; slow, the weak, and the thinly clad soon dieoff.Again and again, in each succeeding generation, thesame thing takes place. By this natural process, which is soinevitable that it cannot be conceived not to act, those bestadapted to live, live those least ; adapted, die. It is sometimessaid that we have no direct evidence of the action ofthis selecting power in nature. But it seems to me we havebetter evidence than even direct observation would be,because it is more universal, viz., the evidence of necessity.It must be so ; for, as all wild animals increase in a geometricalratio, while their actual numbers remain on theaverage stationary, it follows that as many die annually asare born. If, therefore, we deny natural selection, it canonly be by asserting that, in such a case as I have supposed,the strong, the healthy, the swift, the well clad, the wellorganised animals in every respect, have no advantage overdo not on the average live longer than the weak, theunhealthy, the slow, the ill-clad, and the imperfectly organisedindividuals ;and this no sane man has yet been found hardyenough to assert. But this is not all ;for the offspring onthe average resemble their parents, and the selected portionof each succeeding generationwill therefore be stronger,swifter, and more thickly furred than the last ;and if thisprocess goes on for thousands of generations, our animal willhave again become thoroughly in harmony with the new con-

170 NATURAL SELECTION ^ vintiesof" mankind approximated more closely than they do atthe present day. At the same time this is but negativeevidence. A condition of immobility for four or five thousandyears does not preclude an advance at an earlier epoch,and if we can show that there are causes in nature whichwould check any further physical change when certain conditionswere fulfilled does not even render such an advanceimprobable, if there are any general arguments to be adducedin its favour. Such a cause, I believe, does exist ;and Ishall now endeavour to point out its nature and its mode ofoperation.Outline of the Theory of Natural SelectionIn order to make my argument intelligible, it is necessaryfor me to explain very briefly the theory of natural selectionpromulgated by Mr. Darwin, and the power which itpossesses of modifying the forms of animals and plants. Thegrand feature in the multiplication of organic life is, thatclose general resemblance is combined with more or lessindividual variation. The child resembles its parents orancestors more or less closely in all its peculiarities, deformities,or beauties it resembles them in; general more than itdoes any other individuals ; yet children of the same parentsare not all alike, and it often happens that they differ veryconsiderably from their parents and from each other. Thisis equally true of man, of all animals, and of all plants.Moreover, it is found that individuals do not differ from theirparents in certain particulars only, while in all others theyare exact duplicates of them. Theydiffer from them andfrom each other in every particular in form, in : size, incolour ;in the structure of internal as well as of externalorgans in those;subtle peculiarities which produce differencesof constitution, as well as in those still more subtle oneswhich lead to modifications of mind and character. In otherwords, in every possible way, in every organ, and in everyfunction, individuals of the same stock vary.Now, health, strength, and long life are the results of aharmony between the individual and the universe that surroundsit. Let us suppose that at any given moment thisharmony is perfect. A certain animal is exactly fitted to

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