THE PAST EVOLUTION OF MAN 95 



Indeed some students aver — not forgetting the 

 Javanese evidence — that the cradle of the race 

 may have been not Asia, but a lost continent over 

 which the southern waters now roll. 



And this raises the last question to be noted — 

 very briefly — in this long chapter. How old is the 

 human race ? Properly to discuss the grounds on 

 which an answer to this question may be based 

 would entail the consideration of many geological 

 facts and inferences. But assuming that the data 

 from which students have constructed the geological 

 time-table are trustworthy, and thereafter noting the 

 lowest levels at which human remains have been 

 found, and taking into account such further evidence 

 as is available, we may assert, with due qualifications, 

 that in all probability the human race is about two 

 hundred and fifty thousand years old. To those 

 who have never concerned themselves with geology, 

 and who estimate time rather by the length of the 

 individual life or the epochs of historians than by 

 the cosmic standards, this period of a quarter of a 

 million years may seem very long. But to many of 

 us, who are less in the thrall of these very inade- 

 quate units of measurement, the period allotted for 

 the evolution of man as we know him at his best, 

 from man as he must once have been, seems very 

 short. Shorter still does it seem when we consider 

 the estimates — based upon the rate of solar shrink- 

 age, and (later) upon the known facts as to the 

 terrestrial distribution of radium — that have been 

 made as to the period of time which must elapse 

 " till the sun grows cold," and human life as we 

 know it ceases to be possible. I have elsewhere 



