90 MAN THE ANIMAL 



roughly three hundred years a 4.7-fold multiplication of human 

 beings on the face of the earth, and this present cycle of growth 

 appears to be only about two-thirds completed. A nearly five- 

 fold net multiplication of the population of a species with such 

 relatively poor reproductivity as man displays, in a time period 

 of only about three hundred years, is certainly a noteworthy 

 phenomenon demanding the most serious consideration. 



But man, as a distinct and differentiated species, had been on 

 the earth an extremely long time prior to the seventeenth cen- 

 tury. Few, if any, anthropologists nowadays question that he 

 had become differentiated and was making flint tools of the 

 pre-Chellan type early in the Quaternary, certainly some- 

 where in the first inter-glacial period. Nor is it doubted that 

 from at least that time he has continued on the earth in an 

 unbroken succession of generations j through the long second 

 and third inter-glacial periods and the glaciations that separated 

 them. Geologists, anthropologists and archaeologists seem, how- 

 ever, not to have been able, up to very recent times, to agree 

 as to the number of calendar years it took man to climb this 

 long evolutionary ladder. Lately, however, Zeuner has syn- 

 thesized all the evidence in a masterly way, with results that 

 warrant and appear to be receiving general acceptance, so that 

 it may be hoped that the timing of prehistory may be at last 

 regarded as reasonably settled. He reaches the conclusion that 

 Homo heidelbergensis from the Mauer sands (the oldest find 

 in Central Europe) has a probable date on the absolute time 

 scale of about 500,000 years before 1800 a.d. 



So then the following situation is presented for our con- 

 sideration. In the 500,000 odd years from the time that man 

 got under way as a distinct zoological entity, up to about 1 630-50 

 say, he had certainly increased in numbers in the normal bio- 

 logical way of things. He may be presumed to have multiplied 

 during these years as rapidly, on the whole, as his inherent 

 biological equipment and the circumstances of his natural en- 

 vironment would permit. Yet the total world population in 

 1630 was only 445 million, with a density of a little over eight 

 persons per square mile as against the present forty-one. 



