2 ARBOREAL NAN 



the opening period of hasty and unreasoning partisanship 

 was passed, and after the first skirmishes had been fought 

 and won for the principle of evolution, there still remained 

 the biggest battle of all to be contested. Fifty years ago 

 even an ardent evolutionist would feel no difficulty in 

 keeping as a mental reservation the belief that, though 

 no doubt the lesser beasts had been subject to the laws 

 of gradual change, Man was aloof from all this and was a 

 divine, a special, and a perfected creation. This mental 

 reservation is, not unnaturally, still prevalent to-day; 

 and I think that in 1916 one would give but an ill picture 

 of the popular progress of the ideas first made definite 

 by the work of Darwin, if one assumed that, in the dying 

 of controversy, there had of necessity been a really wide 

 acceptance of the picture of a simple evolutionary origin 

 of Man. How completely Man can be separated, by a 

 series of mental processes, from all the laws known to 

 govern the modifications and progress of lower animals, 

 even by a man of the highest scientific attainments, may 

 be realized by the reading of such a work as the final 

 effort of Thomas Dwight, the late distinguished Pro- 

 fessor of Anatomy of Harvard. What Dwight, pos- 

 sessed of a vast store of knowledge of the structure and 

 variations of Man and the lower animals, could do, a 

 great host of others can do in the comfortable absence 

 of any such precise knowledge which might influence the 

 attitude they elected to adopt. 



Still, despite the mental reservations of the thinking 

 few, and the unthinking many, the questions must be 

 asked and answered: What are the factors of habit or 

 environment, and what are the steps of " adaptation," 

 " variation," or " sporting " which have led to the evolu- 

 tion of Man as a zoological type ? 



We start, therefore, with the assumption that we accept 

 the principle of evolution as a fact, and that we extend 

 this principle to embrace Man. " Adaptation," "varia- 

 tion," and " sporting " have been named in that order of 



