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Show 112 THE DESCENT OF 1\IAN. PART I. any other animnl. Some savage races, such as the Australians, are not exposed to more diversified c?nditions than are many species which have very Wide ranges. In another and much more ~mportant r~spect, man differs widely from any stnct1y domesticated animal ; for his breeding has not been controlled, either throuo·h methodical or unconscious selection. No race or bod; of men has been so completely subjugated by other men, that certain individuals have Lee~ pr~sened and thus unconsciously selected, from bemg m some wfty more useful to their masters. Nor have certain male and female individuals been intentionally picked out and matched, except in the well-known case of the Prussian grenadiers; and in this case man obeyed, as might have been expected, the law of methodical selection; for it is asserted that many tall men were reared in the villages inhabited by the grenadiers with their tall wives. If we consider all the races of man, as forming a single species, his range is enormous; but some separate races, as the Americans and Polynesians, have very wide ranges. It is a well-known law that widely-ranging species are much more variable than species with restricted ranges; and the variability of man may with more truth be compared with that of widely-ranging species, than with that of domesticated animals. Not only does variability appear to be induced in man and the lower animals by the same general causes, but in both the same characters are affected in a closely analogous manner. This has been proved in such full detail by Goclron and Quatrefages, that I need here only refer to their works.13 Monstrosities, which gra- 13 Godron, 'De l'Espcce,' 1859, tom. ii. livre 3. Quatrcfages, 'Unite de l'Espece Humaine,' 1861. Also Lectures on Anthropology, given in the • Revue des Cours Scientifiques,' 1866-1868. CrrAP. IV. 1\IANNER OF DEVELOPMENT. 113 duate into slight variations, are likewise so similar in man and the lower animals, that the same classification and the same terms can be used for both, as may be seen in Isidore Geoffroy St.-Hilaire's great work.H This is a necessary consequence of the same laws of ·Change prevailing throughout the animal kingdom. In my work on the variation of domestic animals, I have attempted to arrange in a rude fashion the laws of variation under the following heads :-The direct and definite action of changed conditions, as shewn by all or nearly all the individuals of the same species varying in the same manner under the same circumstances. The effects of the long-continued use or disuse of parts. The cohesion of homologous parts. The variability of multiple parts. Compensation of growth; but of this law I have found no good instances in the case of man. The effects of the mechanical pressure of one part on another; as of the pelvis on the cranium of the infant in the womb. Arrests of development, leading to the diminution or snppression of parts. The reappearance of long-lost characters through reversion. And lastly, correlated variation. All these so-called Jaws apply equally to man and the lower animals; and most of them even to plants. It would be superfluous here to discuss all of them; 10 but several are so important for us, that they must be treated at considerable length. The direct and d~finite action of changed conditions.This is a most perplexing suqject. It cannot be denied 14 'Hist. Gen. et Part. des Anomalies de !'Organisation,' in fllree volumes, tom. i. 1832. 15 I have fully discussed these laws in my 'Vnriation of Animals and Plants under Domestication,' vol. ii. chap. xxii. and xxiii. :J.\<1. J. F. DUl'ancl has lately (1868) published a valuable essay ' De l'In:fl.uence des Milieux, &c.' He lays much stress on the nature of the soil. VOL. L I |
