With every throb of the climatic pulse which we have felt in Central Asia,, the centre of civilisation has moved this way and that. Each throb has sent pain and decay to the lands whose day was done, life and vigour to those whose day was yet to be.

For the source of any characteristic so widespread and uniform as this adaptation to environment we must go back to the very beginning of the human race.

Geologists are rapidly becoming convinced that the mammals spread from their central Asian point of origin largely because of great variations in climate.

Man could not stay there forever. He was bound to spread to new regions, partly because of his innate migratory tendency and partly because of Nature's stern urgency.

In America the most widespread type of forest is the evergreen coniferous woodland of the north.

The buffalo is a surprisingly stupid animal.

Although mountains may guide migrations, the plains are the regions where people dwell in greatest numbers.