252 



SEXUAL SELECTION: MAMMALS. 



[Part II. 



little laterally, increase so much in length during old age, 

 and curve so much upward, that they can be used as a 

 means of attack. Nevertheless an old boar is not so dan- 

 gerous to man as one at the age of six or seven years. 35 



In the full-grown male Babirusa pig of Celebes (Fig. 

 64), the lower tusks are formidable weapons, like those of 



Fig. 64.— Skull of the Babirusa Pig (from Wallace's 'Malay Archipelago'). 



the European boar in the prime of life, while the upper 

 tusks are so long and have their points so much curled 

 inward, sometimes even touching tbe forehead, that they 

 are utterly useless as weapons of attack. They more near- 

 ly resemble horns than teeth, and are so manifestly useless 

 as teeth that the animal was formerly supposed to rest 

 his head by hooking them on to a branch. Their convex 



S5 Brehm, ' Thierleben,' B. ii. s. 729, 732. 



