SOCIAL EVOLUTION 121 



from the pre-historic remains, early man was not 

 social, and did not live in groups until the Ice Age. 

 So we may fairly infer that the clan or tribe, the 

 social group, was formed by the clinging together of 

 families, not the family evolved out of the social 

 group; and that this occurred late. 



Now, the geological record throws a very important 

 light on this. During all that long period when early 

 man was merely creeping upward, so to say, the 

 climate of Europe was much warmer and better than 

 it is to-day. At first it was like the climate of Algeria ; 

 later like the climate of Australia. Men had plenty 

 of primitive food, and no need for fire, clothing, or 

 houses. But it was again growing steadily colder. 

 All the great mountain chains of our world were rising, 

 and when they reached their culmination a great 

 Ice Age set in. Five times in succession, with com- 

 paratively warm periods between, a sheet of ice and 

 snow spread from the mountains over Europe and 

 North America; and there were other sheets wherever 

 there were high mountains. At the fourth and great- 

 est spread of the ice-sheet Europe was glacial as far 

 south as the Thames and the Danube, and America 

 as far south as St. Louis and New York. 



The pre-historic inhabitants of Europe were driven 

 south, and forced to live in caves. No doubt rock 

 shelters would be used at first, and men would gradu- 

 ally venture into the dark caverns. We find groups 

 huddling in the caves of Derbyshire, and very large 



