HOW THE EARTH WAS PEOPLED. 679 



capricious in such an arrangement of lands and seas, and that there 

 have been, if not always, at least from a very ancient period, emerged 

 lands occupying a considerable part of the northern hemisphere, ad- 

 vancing very far toward the pole, and describing around the Arctic 

 Sea a belt of more or less contiguous countries and islands. This is, in 

 effect, what geology teaches. The changes, immersions, and emersions 

 have never been anything but partial and successive, while the skele- 

 tons of the continents go back to the most remote ages. There have 

 always been a Europe, an Asia, an America, and Arctic lands. We 

 know certainly that there have always been around the Arctic pole ex- 

 tensive territories, if not continents, long the home of the same plants 

 as the rest of the globe, and that, beginning with an epoch that corre- 

 sponds with the end of the Jurassic, the climate, at first as warm there 

 as elsewhere, has tended gradually to become colder. The depression 

 of temperature was at first manifested very slowly, and was far from 

 having attained its present degree in the tertiary ; for the trees that 

 then grew in Greenland the sequoias, magnolias, and plane-trees 

 now attain their full development in Southern Europe, and are not 

 suited with the climate of Central Europe. We are, then, assured of 

 the ancient existence, near the Arctic pole, of a zone of lands covered 

 with a rich vegetation. The permanent existence of a polar sea is 

 none the less attested by fossils from all parts of the region. The 

 neighborhood of the pole was long habitable, and inhabited by man in 

 a time near that in which the vestiges of his industry begin to show 

 themselves alike in Europe and America. In passing thus from the 

 Arctic lands to those bordering on the polar circle, and through the 

 latter into Asia, Europe, and America, man would only have taken 

 the road which a host of plants and animals followed, either before him 

 or at the same time, and under the stress of the same circumstances. 



It is, in fact, by the aid of migrations from the neighborhood of the 

 pole that we can generally explain the phenomenon of scattered or dis- 

 joined species, a phenomenon identical with the one which man of the 

 Old World and man of the New World present when they are compared. 

 Combining present notions with the indications furnished by the fos- 

 sils, we discover numerous examples of disjunction in which allied 

 forms, often hardly distinguishable, have been distributed at the same 

 time in scattered regions, at extremely remote points in the boreal 

 hemisphere, without any apparent connection along the parallels, to ex- 

 plain the common unit. Europe attests by undeniable fossils that it 

 had formerly a host of vegetable types and forms that are now Ameri- 

 can, which it could have received only from the extreme north. It 

 had, for example, magnolias, tulip-trees, sassafras, maples, and pop- 

 lars, comparable in all respects to those which grow in the United 

 States. The two plane-trees, that of the West and that of Asia Minor, 

 to which we may add an extinct fossil European plane-tree, illustrate 

 the same phenomenon of dispersion. Europe in the Tertiary period 



