THE VOYAGE OF EVOLUTION 117 



ing. Even without man's help, however, the extinction has gone 

 on to such a degree that we may well hold up our hands in aston- 

 ishment. If nature by the simple expedient of a cold, stormy 

 period can destroy life so rapidly, can she at the same time produce 

 new forms with equal rapidity? That is what she seems to have 

 done in the Permian and in the earlier crisis when animals left the 

 water. That is what she also did in the last Glacial Period. This 

 time, however, her infinite resourcefulness directed itself toward 

 the evolution of intelligence, and man appeared upon the scene. 

 Yet though her end was so different, this time as formerly, the 

 chief agency that she employed was climate. 



Let us consider briefly the great outstanding fact of the last 

 Glacial Period, that is, the development of the human mind. The 

 history of early man and the climatic changes of this period are 

 summed up in Figure 23. At the beginning of the great climatic 

 pulsations shown in this diagram, we do not know whether 

 there was any such creature as man. In Java, to be sure, there 

 has been found the top of a skull, two teeth, and a thigh bone of 

 an animal too advanced to be an ape, too low to be a man. Vol- 

 umes have been written about these few bones of the "missing 

 link." The brain of Pithecanthropus erectus, or the "erect ape- 

 man" as he is called, was only half as large as that of modern man. 

 His forehead, with its great projecting ridges above the eyes, 

 was so low that there was little room for the frontal lobes where 

 self-control, attention, and the higher mental faculties have their 

 seat. We do not even know whether his powers of consecutive 

 thought enabled him to fashion any implements. He had indeed 

 progressed much beyond the apes in intelligence, but his life was 

 still essentially the same as that of the beasts. * 



Not for hundreds of thousands of years was man to rise to the 

 point where brain triumphed over brawn. On the road to that 

 goal one of the chief time-markers is the Heidelberg jaw. This 

 is the jaw of an apelike, chinless man, but man he surely was. On 

 this one jaw a whole "race" of primitive men has been built up. 



