ANTIQUITY OF MAN 423 



but perhaps the earliest actually human fossil so far known is 

 a lower jaw of very massive form which was found in a 

 deposit of probably early Pleistocene age near Heidelberg, and 

 described by Schoetensack in 1908 under the name Homo 

 heidelbergensis. This name implies that in the opinion of its 

 author the fossil man of Heidelberg was generically, but not 

 specifically, identical with the human beings which now exist. 

 The question of the distinction of species in the genus Homo, 

 however, is, as in most other genera, a very difficult one, and 

 opinions are divided as to whether only one or several species 

 should be recognized amongst the existing races of mankind. 



So close is the anatomical agreement between the genus 

 Homo and the higher apes that there is little room for con- 

 necting links between them, the difficulty being rather to find 

 any definite characters by which they can be separated than to 

 discover reasons for bringing them together. Nevertheless, the 

 gap, small as it is, has been filled by the discovery, by Dr. 

 Dubois in 1894, of the remains of a semi-human, ape-like 

 creature, to which the name Pithecanthropus erectus has been 

 given. These remains were found in Pliocene strata in the 

 island of Java and consist of a portion of a cranium, a thigh 

 bone and two molar teeth. 1 



In deposits of Pleistocene age undoubtedly human remains 

 become fairly abundant, and are found associated with the bones 

 of other mammals, of which many, such as the mammoth, the 

 cave bear and the woolly rhinoceros, are now extinct. 



The chief factors which contributed towards the gradual 

 transformation of ape-like into human creatures were doubtless 

 the same as those which have operated in the evolution of other 

 branches of the animal kingdom, namely, the efforts which the 

 ancestral forms were obliged to make in order to maintain them- 

 selves in the struggle for existence and the natural selection of 

 favourable variations. In no group of the animal kingdom do we 

 see better illustrated the importance of Lamarck's principle of 

 the effect of changed habits upon bodily organization. 2 



The anthropoid ancestors of man were undoubtedly, like 



1 Some authorities regard these remains as truly human. The difference of 

 opinion is itself very instructive. 



2 Darwin, notwithstanding what he says in the sixth edition of the " Origin of 

 Species " about the effects of use and disuse (quoted on p. 392), denies, in the 

 " Descent of Man " (Ed. 2, p. 619), that man has risen through his own exertions. 

 I can see no reason for such a pessimistic view. 



