460 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1930 



quently, the flow of the ice became easier and the rate of movement 

 increased, as is observed in Alpine glaciers far below the snow line. 

 Even mider these conditions a motion of 1 foot per day must be 

 considered as high. However, assuming such a rate, it would take 

 about 11,000 years for the ice to travel the distance of 750 miles 

 from its origin in Scandinavia to northern Germany. 



This figure gives an idea of the length of time required for an 

 ice sheet to move over great distances. It does not, however, give a 

 measure of the advance of the ice border. It is well known that the 

 ice in moving forward melts. The amount of melting is in some 

 cases so considerable that the ice front recedes, although the ice as 

 a whole pushes steadily forward. Thus the front or tongue of the 

 majority of the Alpine glaciers is retreating. The melting process 

 was undoubtedly also active in Pleistocene time ; during the advance 

 of the ice its edge was melting. This wastage may have been small, 

 compared with the motion of the ice, especially when the cold was 

 at its climax; it may have been considerable when the climate was 

 as yet less severe. In any case, on account of this melting, the 

 above figure must be increased by an uncertain amount. To simplify 

 the problem, this factor may be neglected, bearing always in mind 

 that the figure is rather below the real value than above it. 



As the final result of the preceding deductions it can be stated : 

 Thirty thousand years ago man was certainly in Europe, living in a 

 rather warm period preceding the last glaciation. This figure seems 

 to be well established, and no scientist will raise serious objection 

 to it so long as it is regarded as a minimum. 



WHY DO GEOLOGISTS ASSIGN A STILL HIGHER AGE TO MANKIND? 



However, the great majority of geologists and prehistorians as- 

 sume considerably higher figures for the age of the human race. 

 Some reasons for such an assumption have already been alluded to. 

 The rate of movement of the advancing ice seems in all probability 

 to have been less than that assumed in the present paper, and there- 

 fore the time of advance longer. Moreover, the melting of the ice 

 during its advance was neglected. Furthermore, how long was man 

 living in a genial climate before the temperature dropped to such a 

 level that the ice started its advance to the south? There are good 

 geological reasons for concluding that the interglacial period pre- 

 ceding the last glaciation lasted much longer than the postglacial 

 period, which latter had a duration of at least 18,000 years for 

 northern Germany. (PL 3.) If man was already in Europe at the 

 beginning of the last interglacial, then many thousands of years must 

 be added to the above figure. 



Finally, we have to take into account another possibility. The 

 cradle of mankind was hardly in Europe, Even from the purely 



