. The descent of man, and selection in relation to sex. Evolution (Biology); Sexual selection in animals; Sexual dimorphism (Animals); Sex differences; Human beings. Chap. XVII.] MEANS OF DEFENCE. 253 surfaces would, however, if the head were held a little laterally, serve as an excellent guard; and hence, per- haps, it is that in old animals they " are generally broken off, as if by ;'" Here, then, we have the curious case of the upper tusks of the Babirusa regularly assum- ing, during the prime of life, a structure which apparently renders them fitted only for defence
. The descent of man, and selection in relation to sex. Evolution (Biology); Sexual selection in animals; Sexual dimorphism (Animals); Sex differences; Human beings. Chap. XVII.] MEANS OF DEFENCE. 253 surfaces would, however, if the head were held a little laterally, serve as an excellent guard; and hence, per- haps, it is that in old animals they " are generally broken off, as if by ;'" Here, then, we have the curious case of the upper tusks of the Babirusa regularly assum- ing, during the prime of life, a structure which apparently renders them fitted only for defence; while in the Euro- pean boar the lower and opposite tusks assume in a less degree and only during old age nearly the same form, and then serve in like manner solely for Fig. 65.—Head of Ethiopian Wart-hoa:, from 'Proc. Zool. Soc' 1869. (I now find that this drawing represents the head of a female, but it serves to show, on a reduced scale, the characters of the male.) In the wart-hog [Phaeochoerus mthiopicus. Fig. 65) the tusks in the upper jaw of the male curve upward dur- ing the prime of life, and, from being pointed, serve as for- midable weapons. The tusks in the lower jaw are sharper than those in the upper, but from their shortness it seems harHly possible that they can be used as weapons of at- tack. They must, however, greatly strengthen those in the '* See Mr. Wallace's interesting account of this animal, ' The Malay Archipelago,' 1869, vol. i. p. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Darwin, Charles, 1809-1882. New York, D. Appleton and company
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