Crosby uses this term to describe areas of the world outside Europe where Europeans and their culture has largely or completely supplanted native societies. This group includes places like North America, Australia, Argentina, and New Zealand. Each of these areas have large tracts of land that are ecologically and climactically similar to Europe, so European plant and animal species, both wild and domesticated, easily flourished there. Before European colonists arrived, the populations in these areas lived primarily in low density communities, so they did not have exposure to diseases, such as cholera, that thrive in dense populations. They were also unexposed to Eurasian and African diseases like smallpox. The Neo-Europes (apart from New Zealand) are distinct in having populations that arrived during the Pleistocene, when low sea levels allowed long distance travel over newly exposed land, and when the ice melted, these populations were completely cut off from Eurasia and Africa. Certain technologies that spread across the Old World, such as metal smelting, did not reach the Neo-Europes until the native population found themselves defending against European invaders. These and other reasons combined to make the Neo-Europes ripe for conquest.