THE EVOLUTION OF MAN 193 



persisted, that some characters are useful and some are not, and 

 that the former are easily modified by conditions of life, the latter 

 unaffected by such conditions. It must, at any rate, be admitted 

 that usually in studying any group of animals we can certainly 

 distinguish between characters which have no visible relation 

 to the maintenance of life, and others which are necessary or 

 advantageous to that purpose, and it is therefore possible to 

 consider the origin of these two kinds of characters separately. 



The human species, in spite of the attention devoted to 

 anthropology, and although it is to us the most familiar species, 

 has, perhaps, been less studied from the zoological point of 

 view than any other. It is also from this point of view 

 the most difficult, partly because it is our own species, and 

 we cannot get far enough away from it to see it in true per- 

 spective ; partly because it has had such an exceptional history, 

 having spread over the whole earth and become largely 

 independent of physical conditions, that is to say it has attained 

 to a great extent the power of making artificially uniform con- 

 ditions which render it independent of differences of climate, 

 geographical features, and differences of fauna and flora in 

 different habitats. The first question to consider is whether 

 man is a single species or several, and what is his relation 

 to other species. This question, as well as most of the others 

 which I propose to consider in this paper, has been discussed 

 with his usual thoroughness and judgment by Darwin in his 

 Descent of Man, so that I am really only trying to see whether 

 we know any more about these problems than Darwin taught us. 



The chief peculiarities of man, as compared with his nearest 

 allies, the anthropoid apes, are all adaptive and useful characters, 

 namely the erect position, the structure of the hand and foot, 

 and the faculty of articulate speech. Associated with the 

 possession of language are the size and differentiation of the 

 brain, especially of the cerebral hemispheres, and the correlated 

 size and shape of the cranium. The reduction of the jaws, teeth, 

 and face generally is also a characteristic feature, and adaptive 

 to the diminution in the use made of the jaws and teeth in 

 feeding and fighting. If man is regarded as a single species 

 then he affords a conspicuous instance against the doctrine 

 that specific characters are not adaptations, but it must be 

 remembered that the contention is not that no specific characters 

 are adaptive, but that in a vast number of cases several species 



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