360 THE STUDY OF ANIMAL LIFE CHAP. 



direct line of our ancestry. To the Neanderthal line may 

 be referred the Heidelberg man of the early Pleistocene. 

 A second collateral line which has come to nothing is 

 that represented by the Piltdown skull (Eoanthropus 

 dawsoni) of the end of the Pliocene. A third collateral 

 line, perhaps diverging in the Miocene, is represented by 

 Pithecanthropus erectus at the end of the Pliocene. Ac- 

 cording to Keith, these three lines are separate offshoots- 

 all eventually failures diverging from the humanoid stem. 



As it is certain that man could not have arisen from 

 any of the known anthropoid apes, and as it is likely that 

 he arose from a stock common to them and to him, it 

 seems justifiable to date the antiquity of the human 

 race not later than the time when the anthropoid apes 

 are known to have been established as a distinct family. 

 This takes us back to pre-Miocene ages. If we mean 

 by the antiquity of man the period since the human stem 

 differentiated from that which led on to the great anthro- 

 poid apes, it may be estimated (Keith and Sollas) 1 at 

 about two million years. If we mean the period at which 

 the brain of man reached a human level or standard, 

 " we have," says Keith, " reasonable grounds for pre- 

 suming that man had reached the human standard by 

 the commencement of the Pliocene period," -about a 

 million years ago. Amid much uncertainty the general 

 result of recent investigation is clear, that the modern 

 type of man is vastly older than was supposed even in 

 the days of Lyell's Antiquity of Man (1863). 



Converging facts point to the conclusion that man 

 arose as a mutation (a discontinuous variation of con- 

 siderable magnitude) in a stock common to him and to 

 the anthropoid apes. In regard to the factors which 

 helped to secure man's ascent we can only speculate. 2 



(a) From what we know of men and monkeys, it seems 

 likely that in the struggles of primitive man cunning 

 was more important than strength, and if intelligence 

 now became, more than ever before, the condition of 

 life or death, wits would tend to develop rapidly. 



1 Sollas, Ancient Hunters, 1911. 



2 The author's Outlines of Zoology, 6th edition, 1914, p. 293. 



