594 THE POPULAR SCIENCE MONTHLY 



THE PALEONTOLOGIC RECORD 

 THE BIRTHPLACE OF MAN 



By Peofessob S. W. WILLISTON 



THE UNIVERSITY OF CHICAGO 



VARIOUS writers, from Le Conte to Smith Woodward, have spoken 

 of critical or rhythmical periods in evolution, periods when evo- 

 lutionary forces have acted more vigorously than at others, with inter- 

 vals of relative quiescence. What these forces are and have been we 

 are not yet sure, whether extrinsic, that is, environmental or Lamarck- 

 ian, or intrinsic, that is, orthogenetic, teleological or what not. Per- 

 haps we shall sometime be more certain of the basal causes of evo- 

 lution, for the paleontologist at least is not satisfied with the crass 

 ignorance of our Weismannian friends who impute the beginning of all 

 things to mere chance. Perhaps when we do know these fundamental 

 causes we shall understand better why evolution has been rhythmical, 

 if such was really the case, as some of us believe with Woodward. 



But, whether there have been internal forces which have had 

 chiefly to do with the rhythm of evolution, or whether such critical 

 periods in the evolution of organic life have been due solely to the 

 larger cosmic forces, I think we shall all admit that there have been 

 critical places of organic evolution, places upon the earth where evolu- 

 tion has advanced with more rapid pace than in others, places per- 

 haps where environmental conditions have conspired to hasten the de- 

 velopment of life, or of particular groups, classes or kingdoms of life. 



Such a critical period, at least for the higher organisms, it seems to 

 me, was the early Pliocene; such a critical place was central Asia; and 

 both together resulted in the birth of man. 



It is a curious fact that nearly all our domestic animals had their 

 origin in Asia. It is also a curious fact that the domestic animals are, 

 almost without exception, the crowning ends of their respective lines 

 of descent, the most highly specialized of their kinds. The genus Bos, 

 the most highly developed of the even-toed ungulates began, to the 

 best of our present knowledge, in the Lower Pliocene of India. And 

 its four distinctive types likewise first appeared there: the Bubalus 

 group, including the domestic buffalo of India, and its untamable kin 

 of Africa; the group that is represented by the domesticated humped 

 oxen of India and their wild relatives of Africa ; the bison strain which 

 spread in Pleistocene times almost to the remote corners of the earth; 



