to buy its experience. The thing which has kept up the necessity of more migration or more power over Nature has been increase of population. Where population has become chronically excessive, and where the population has succumbed and sunk, instead of developing energy enough for a new advance, there races have degenerated and settled into permanent barbarism. They have lost the power to rise again, and have made no inventions. Where life has been so easy and ample that it cost no effort, few improvements have been made. It is in the middle range, with enough social pressure to make energy needful, and not enough social pressure to produce despair, that the most progress has been made.
At first all labor was forced. Men forced it on women, who were drudges and slaves. Men reserved for themselves only the work of hunting or war. Strange and often horrible shadows of all the old primitive barbarism are now to be found in the slums of great cities, and in the lowest groups of men, in the midst of civilized nations. Men impose labor on women in some such groups to-day. Through various grades of slavery, serfdom, villainage, and through various organizations
