CLIMATE OF PLEISTOCENE PERIOD. 37 



Palaeolithic times the European coast extended only a little 

 distance farther into the Atlantic, we may well ask how the 

 presence of the reindeer in the south of France and the hippo- 

 potamus in the north of England can be accounted for. Owing 

 to their geographical position, the north-western regions of our 

 continent could not possibly have been subjected to a climate at 

 all comparable with that of Siberia. The influence of the neigh- 

 bouring Atlantic would effectually prevent the occurrence of 

 strongly-contrasted seasons. We may therefore at once dismiss 

 the hypothesis of great annual migrations which some writers 

 have advanced to account for the startling association in Palaeo- 

 lithic deposits of such discordant species as reindeer and hippo- 

 potamuses, musk-sheep and elephants. The fauna of Palaeo- 

 lithic times comprised, as we have seen, not only northern and 

 temperate forms, but a well-marked group of southern animals. 

 According to the migration -hypothesis, therefore, we are to 

 suppose that in summer huge pachyderms like the elephant 

 and hippopotamus migrated from the south of Europe as far north 

 as England, and that on the approach of winter they returned 

 to their " head-quarters," and were followed by the reindeer and 

 its congeners as far as the foot of the Alps and the Pyrenees. 

 Such a supposition, however, is manifestly unreasonable, inas- 

 much as it is opposed to all that we know of the habits of hip- 

 popotamuses, elephants, and rhinoceroses ; and the same might 

 be said of several other species that belong to the southern 

 group of Palaeolithic times. How impossible, indeed, does it 

 seem that those unwieldy pachyderms could in one year tra- 

 verse the whole breadth of Europe, so as to trespass on the 

 territory of the reindeer and the musk-sheep, and then retreat 

 with sufficient rapidity to escape the severity of a winter before 

 which the arctic mammals were forced to flee to the south of 

 France. 



The anomalous commingling of northern, southern, and 

 temperate forms points, not to one prolonged period character- 

 ised by extreme summers and winters, but to changes of climate 

 very gradually effected through a long course of time. "We may 



