BERING STRAIT LAND BRIDGE 99 



theory of its origin and nature which appear to me to agree 

 better with the geological history of the boreal fauna and flora, 

 as far as we are able to ascertain them, than the hypotheses 

 which have been so widely accepted by scientific men. 



Professor Shaler * reminds us that the extension of rela- 

 tively warm climates which has occurred at certain stages 

 of the Earth's history is perhaps explicable in an equally 

 simple manner as that of the Glacial Epoch. He expresses 

 the belief that if Bering Strait were as rea'dily open to the 

 warm stream of the Pacific or " Kuroshiwo " as the Atlantic 

 is open to the Gulf Stream, the temperature of the region about 

 the North Pole would be lifted by at least thirty degrees above 

 its present mean annual. Indeed, if the Glacial Epoch had 

 been due to a simultaneous closing of the Arctic Ocean to the 

 genial influences of both Atlantic and Pacific, a mild climate 

 all over the Arctic Regions must have coincided with a more 

 copious flow of the " Kuroshiwo " into the Arctic Ocean. And 

 here apparently lies the great stumbling block to my theory 

 on the origin of the Glacial Epoch. If the warmer tempera- 

 ture in the Arctic Regions in Miocene and Oligocene times 

 had been due to a wider Bering Strait, and, consequently, to 

 the fact that a greater volume of the " Kuroshiwo " then 

 poured into the Arctic Ocean, how are we to account for the 

 faunistic affinities existing between Asia and North America 

 during this part of the Tertiary Era ? There are numbers of 

 animals in North America which have an Asiatic ancestry, hut 

 could not have entered the Continent with the great invasion 

 that I described as crossing the Bering Strait land bridge. 

 These and many other facts point to the existence of a land 

 bridge between Asia and North America in early Tertiary 

 times. All the same, several important features imply that 

 before the Pliocene Period the " Kuroshiwo " really sent its 

 warm waters altogether to the Arctic Ocean. 



As I mentioned above, no Japanese affinities are recognis- 

 able in the American Miocene marine fauna. On the other 

 hand, there is some evidence that the Miocene floras of 

 Sakhalin and Japan were intimately related to the Miocene 

 flora of North America. These apparently contradictory 



* Shaler, N. S., " Nature and Man in America," p. 143. 



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