25 o THE POPULAR SCIENCE MONTHLY. 



their neighbors are of comparatively recent date, and that their adap- 

 tation to an aquatic life is a thing but of yesterday when compared 

 with the duration of previous neons in the history of our globe. 



Gentleman's Magazine. 



A PROBLEM IN HUMAN EVOLUTION. 



By Professor GKANT ALLEN. 



" ~| TARDLY any view advanced in this work," says the illustrious 

 -J L author of the " Descent of Man," " has met with so much dis- 

 favor as the explanation of the loss of hair in mankind through sexual 

 selection." Indeed, the friends and foes of Mr. Darwin's great theories 

 have been equally ready, the one party to disclaim and the other party 

 to ridicule the account which the founder of modern philosophic biol- 

 ogy has given of the process whereby man, as he supposes, gradually 

 lost the common hairy covering of other mammalia. Mr. Wallace, 

 with all his ability and ingenuity, finds it necessary to call in the aid 

 of a deus ex machina to explain the absence of so useful and desirable 

 an adjunct ; for he believes that natural selection could never have 

 produced this result, and he therefore feels compelled to put it off 

 upon " some intelligent power," since he denies altogether the exist- 

 ence of sexual selection as a vera causa. Mr. J. J. Murphy, in his 

 recently published revision of " Habit and Intelligence," has taken up 

 the same ground with a more directly hostile intent ; and Spengel has 

 also forcibly given expression to his dissent on the plea of inadequate 

 evidence for the supposed preference. It seems highly desirable, 

 therefore, to prop up Mr. Darwin's theory by any external supports 

 which observation or analogy may suggest, and if possible to show 

 some original groundwork in the shape of a natural tendency to hair- 

 lessness, upon which sexual selection might afterward exert itself so as 

 to increase and accelerate the depilatory process when once set up. 



The curious facts for which we have to account are something 

 more than the mere general hairlessness of the human species. In 

 man alone, as Mr. Wallace clearly puts the case, " the hairy covering 

 of the body has almost totally disappeared ; and, what is very re- 

 markable, it has disappeared more completely from the back than 

 from any other part of the body. Bearded and beardless races alike 

 have the back smooth, and even when a considerable quantity of hair 

 appears on the limbs and breast, the back, and especially the spinal 

 region, is absolutely free, thus completely reversing the characteristics 

 of all other mammalia." When we consider the comparatively help- 

 less condition to which man has been thus reduced, as well as the 

 almost universal human practice of substituting artificial clothing, 



