As a an aside to MALONE'S thread i wanted to ask an interesting side that i have not seen or thought thru before.
Lets say the New World in 1492 was advanced in certain ways as the old world. This would include :
1. Domestication of new world animals and these animals are in close proximity to the owners as in the old world.
2. Cities have been around longer so population overcrowding is common, creating a great filthily environment for disease (equal to European cities)
3.Trade routes are well established (they were very solid in the New World)
4. Wheel widely used and some small ships so some trade between the islands from Central American and North America
Utilizing the books, Guns Germs & Steel, The lost city of the Monkey God, and The silk road each have the same basic story of disease spread, civilizations wiped out, and desolation of government. Now the key ingredient in the native population decimation in the New World was the waves of disease that were spread (Plague, influenza, small poz, chicken pox, Typhoid, etc etc ), with each wave wiping out a group that survived the preceding outbreak.
Ok now Columbus arrives in the islands, DR, Cuba, and others. He finds some semi advanced ports or towns and (in Columbus own log he expresses surprise on how healthy the crew was on the first voyage) does some trade. Disease spreads in the ships and he makes it back to Spain with some infection spread. However on subsequent voyages the Spanish are always decimated by disease and perhaps bring significant new disease back to Europe. Here you have the reverse of the New World kill off (the disease would be different or at least different species). It would still impact and devastate the new world however perhaps the waves are much slower plus no invasion by the Spanish armies.