Why did such meteoric intellectual brilliancy occur in Greece? Why are such wonderful Hindu ruins located in Cambodia in Indo-China? What has a high type of culture been able to persist for a thousand years in stormy Iceland? And why do we see in China the curious anomaly of a progressive South & a conservative North? After years of search, Mr. Huntington believes that at least a partial explanation is found in natural selection arising most frequently under the stress of over-population & migration. The principle involved is so simple & obvious that it seems almost incredible that it has been so largely ignored by students of geography, history & sociology. This work is the result of his research.