Many civilizations arose because they were the "optimum size" (for their time), and then fell when they ceased to be the optimum size.
It's interesting that the early civilizations started in peninsulas. Such places had good water transportation, and one land connection.
This basically describes Babylon, between the Tigris and Eurphrates Rivers, and the part of Egypt between the Nile and the Red Sea. India is one large (too large) peninsula, as was "China" (the part between the Yellow and Yangtze Rivers).
Greece and Rome rose when they did because they were peninsulas that were optimum size for their time. Similar things could be said about England (an island), as well as Spain and France (peninsulas) in their time. The purpose of the Erie Canal was to turn the eastern United States into one large "peninsula between the Great Lakes, the Mississippi River, and the Atlantic Ocean.
The rise of the BRICs is occurring now because they are optimum size for OUR time. India and China, as large peninsulas, are now coming into their own. Russia and Brazil, although larger (than Chine ex the Himalays, etc.) may be similarly regarded. The only other country in the world of comparable size (more than 1 million square miles and more than 100 million people), is the United States.