In today's excerpt--70% of the world's population resides on just 7% of the world's land:
"Today, there are just over 6 billion people on earth. Six hundred years ago, in 1400, humankind was just 6 percent of that, or about 350 million, slightly more than the current population of the United States. ... The 350 million people living in 1400 were not uniformly distributed across the face of the earth, but rather clustered in a very few pockets of much higher density. Indeed, of the 60 million square miles of dry land on earth, most people lived on just 4.25 million square miles, or barely 7 percent of the dry land. The reason, of course, is that that land was the most suitable for agriculture, the rest being covered by swamp, steppe, desert, or ice.
"Moreover, those densely populated regions of earth corresponded to just fifteen highly developed civilizations, the most notable being (from east to west) Japan, Korea, China, Indonesia, Indonesia, Indochina, the Islamic West Asia, Europe, Aztec, and Inca. Astoundingly, nearly all of the 350 million people alive in 1400 lived in a handful of civilizations occupying a very small proportion of the earth's surface. Even more astoundingly, that still holds true today: 70 percent of the world's six billion people live on those same 4.25 million square miles.
Robert B. Marks, The Origins of the Modern World, Rowman and Littlefield, Copyright 2007 by Rowman and Littlefield Publishers, pp. 23-24.