446 DARWINISM chap. 



them. He possesses the same number of limbs terminating 

 in the same number of digits as belong fundamentally to the 

 mammalian class. His senses are identical with theirs, and 

 his organs of sense are the same in number and occupy the 

 same relative position. Every detail of structure which is 

 common to the mammalia as a class is found also in mam 

 while he only differs from them in such ways and degrees as 

 the various species or groups of mammals differ from each 

 other. If, then, we have good reason to believe that every 

 existing group of mammalia has descended from some common 

 ancestral form — as we saw to be so completely demonstrated 

 in the case of the horse tribe, — and that each family, each 

 order, and even the whole class must similarly have de- 

 scended from some much more ancient and more generalised 

 type, it would be in the highest degree improbable — so 

 improbable as to be almost inconceivable — that man, agreeing 

 with them so closely in every detail of his structure, should 

 have had some quite distinct mode of origin. Let us, then, 

 see what other evidence bears upon the question, and whether 

 it is sufficient to convert the probability of his animal origin 

 into a practical certainty. 



Rudiments and Variations as Indicating the Relation of Man to 

 other Mammals. 



All the higher animals present rudiments of organs which, 

 though useless to them, are useful in some allied group, and 

 are believed to have descended from a common ancestor in 

 which they were useful. Thus there are in ruminants rudi- 

 ments of incisor teeth which, in some species, never cut through 

 the gums ; many lizards have external rudimentary legs ; 

 while many birds, as the Apteryx, have quite rudimentary 

 wings. Now man possesses similar rudiments, sometimes 

 constantly, sometimes only occasionally present, which serve 

 intimately to connect his bodily structure with that of the 

 lower animals. Many animals, for example, have a special 

 muscle for moving or twitching the skin. In man there are 

 remnants of this in certain parts of the body, especially in 

 the forehead, enabling us to raise our eyebrows ; but some 

 persons have it in other parts. A few persons are able to move 

 the whole scalp so as to throw off any object placed on the head, 



