42 ORIGIN OF LIFE IN AMERICA 



Epoch do not seem to me to harmonise at all with the geo- 

 graphical distribution of animals and plants. If we assume 

 that an arctic climate prevailed at that time all over Canada 

 and the northern United States, we are faced by numerous 

 difficulties. The biological evidence favours the view that the 

 climate in boreal North America, though much more humid 

 than at present, so that it led to extensive glaciation on all 

 higher mountain ranges, was not arctic but temperate, and 

 that in many parts within the so-called glaciated area there 

 existed islands where life was abundant and survived to the 

 present day. 



Let us return to the animals and plants inhabiting the 

 White Mountains. Their relationship is almost altogether 

 with Lapland and Greenland, and yet that affinity has clearly 

 been brought about at a much earlier date than that of the 

 arrival of the European element m North America. 



During the Pliocene Period movements seem to have taken 

 placo resulting in an increased height of land. This need not 

 necessarily have affected the whole of North America. It was 

 probably more or less confined to the north-eastern and north- 

 western parts. While the closing of the North Atlantic left 

 the coastal districts open to the beneficial influence of the 

 Gulf Stream, the temperate fauna and flora must have gradu- 

 ally disappeared from the more inland boreal parts of the con- 

 tinent, thus leaving room for the expansion of the arctic 

 animals and plants in various directions. It was during the 

 Pliocene Period, I think, or earlier, and, at any rate, long 

 before the commencement of the Glacial Epoch, that the 

 animals and plants from Labrador thus found their way south- 

 ward to the White Mountains. However, 1 shall bring forward 

 further evidence later on which will throw additional light 

 on the problems I have discussed. 



The theory that the animals and plants were driven south 

 of the ice foot or southern margin of the supposed great 

 ice-sheet ought to be supported by biological evidence. 



Theoretically it is assumed that the barren-ground or arctic 

 fauna and flora lived close to this margin, as already stated, 

 and the temperate forms further south. The only fossil evi- 

 dences we possess of arctic animals having actually lived south 

 of the ice-sheet, or, as we might say, south of the limits of 



