202 



EVOLUTION AND GENETICS 



Forced from their arboreal homes by the search for food and by 

 inadequacy of the thinning forests for a wide range of movement, 

 they would immediately encounter the conditions of a semi- 

 terrestrial life, with its manifold advantages and demands. To 

 these they must have responded if they were to exist, and by their 

 remains we see that they existed. 



Subsequent to the first glaciation a second occurred in the early 

 Pleistocene, and a third and fourth later in the same epoch. These 

 resulted in fluctuations of climate, but a relative alnmdance of 

 fossil remains of man shows that his development had reached a 

 point where changing conditions could be met by his improving 

 intelligence. The remains with which we deal are not as highly 

 developed as modern man; we are forced to look upon them as 

 different species; but all authorities agree that they are definitely 

 above the status of the apes. Moreover they are associated with 

 implements of stone and other evidences of culture which have 

 never been acquired by other animals. 



Three species of fossil men are recognized in addition to remains 

 referable to Homo sapiens. These are Homo heidelhergensis, Homo 



neanderthalensis and Eoan- 

 thropus dawsoni. Of these 

 the second is represented by 

 many specimens, while the 

 other two are based on limited 

 material. 



Heidelberg Man. Homo 

 heidelhergensis is based on a 

 jaw found near Heidelberg in 

 1907. The bone was in ex- 

 cellent condition and con- 

 tained a full set of lower 

 teeth (Fig. 116). Osborn, quoting from Schoetensack, the 

 author of the species, gives the following account of the speci- 

 men: "The mandible shows a combination of features never 

 before found in any fossil or recent man. The protrusion of the 

 lower jaw just below the front teeth which gives shape to the 

 human chin is entirely lacking. Had the teeth been absent it 

 would have been impossible to diagnose it as human. From a 

 fragment of the symphysis of the jaw it might well have been 

 classed as some gorilla-like anthropoid, while the ascending ramus 



Fig. 116. — Jaw of Heidelberg man, Homo 

 heidelhergensis. (From Lull, after 

 Schuchert and Woodward.) 



