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Show 154: THE DESCENT OF M.A.N. PART I. naturally follow from the assumed uniformity of the exciting causes, and likewise from the free intercrossing of many individuals. The same organism might acquire in this manner during successive periods successive modifications, and these would be transmitted in a nearly uniform state as long as the exciting causes remained the same and there was free intercrossing. With respect to the exciting causes we can only say, as when speaking of so-called spontaneous variations, that they relate much more closely to the constitution of the varying organism, than to the nature of the conditions to which it has been subjected. Conclusion.-In this chapter we have seen that as man at the present day is liable, like every other animal, to multiform individual differences or slight variations, so no doubt were the early progenitors of man; the variations being then as now induced by the same general -causes, and governed by the same general and complex laws. As all animals tend to multiply beyond their means of subsistence, so it must have been with the progenitors of man; and this will inevitably have led to a struggle for existence and to natural selection. This latter process will have been greatly aided by the inherited effects of the increased use of parts ; these two processes incessantly reacting on each other. It appears, also, as we shall hereafter see, that various unimportant characters have been acquired by man through sexual selection. An unexplained residuum of change, perhaps a large one, must be left to the assumed uniform action of those unknown ao·encies which occasionally induce strongly-mat·ked and0abrup~ ·deviations of structure in our domestic productions. Judging from the habits of savages and of the greater number of the Quadrumana, primeval men, and even CIIAP. IV. MANNER OF DEVELOPMENT. 155 the ape-like progenitors ~f m~n, pro~ably lived . in society. With strictly somal amma~s, ~~tural selectiOn sometimes acts indirectly on the md1vidual, ~hrough the preservation of variations whi?h a:re be~efimal only to the community. A community mcludm?' a large number of well-endowed individuals increases m number and is victorious over other and less well-endowed communities; although each separate member may gain no · advantage over the other members of the same community. With associated insects ma~y remar~abl.e .structures, which are of little or no serviCe to the I~dividual or its own offspring, such as the pollen-collectmg apparatus, or the sting of the worker-bee, or . the great jaws of soldier-ants, have been thus acqmred. With the higher social animals, I am not aware that .any structure has been modified solely for the good. of the community, though some are of se?ondary serviCe to it. For instance, the horns of rummants and the great canine teeth of baboons appear to have been acquired by the males as weapons for sexual strife, but they are used in defence of the herd or troop. In regard to certain mental faculties the case,. as we shall see in the following chapter, is wholly different.; for these faculties have been chiefly, or even exclusively, gained for the benefit of the ~omm':nity; the individuals composing the commumty bemg at the same time indirectly benefited. It has often been objected to such views as the fore< roinO' that man is one of the most helpless and defenceless ~~eatures in the world; and that during his early and less well-developed condition he would h~ve been still more helpless. The Duke of Argyll, for mstance, insists 81 that " the human frame has diverged from 81 ' Primeval Man,' 1869, p. 66. |