. The descent of man, and selection in relation to sex. Evolution; Natural selection; Heredity; Human beings -- Origin. Chap. XVII. Mammals—Means of Defence. 519 laterally, would serve as an excellent guard; and hence, perhaps, it is that in old animals they " are generally broken off, as if by " ;40 Here, then, we have the curious case of the upper tusks of the Babirusa regularly assuming during the prime of life, a structure which apparently renders them fitted only for defence; whilst in the European boar the lower tusks assume in a less degree and only during old ag
. The descent of man, and selection in relation to sex. Evolution; Natural selection; Heredity; Human beings -- Origin. Chap. XVII. Mammals—Means of Defence. 519 laterally, would serve as an excellent guard; and hence, perhaps, it is that in old animals they " are generally broken off, as if by " ;40 Here, then, we have the curious case of the upper tusks of the Babirusa regularly assuming during the prime of life, a structure which apparently renders them fitted only for defence; whilst in the European boar the lower tusks assume in a less degree and only during old age, nearly the same form, and then serve in like manner solely for Fig. <:6. Skull of the Babirusa Pig (from Wallace's ' Malay Ai chipdago')• In the wart-hog (Phacochoerus cethiopicus, fig. 67) the tusks in the upper jaw of the male curve upwards ..during the prime of life, and from being pointed serve as formidable weapons. The tusks in the lower jaw are sharper than those in the upper, but from their shortness it seems hardly possible that they can be used as weapons of attack. They must, however, greatly strengthen those in the upper jaw, from being ground so as to fit closely against their bases. Neither the upper nor the lower 40 See Mi\ 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, Appleton
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