last ice age severed links between Eurasia and the Americas, and there was hardly any communication between Eurasia and Australasia or with the islands of the western Pacific, some of which were settled as early as thirty thousand years ago. In effect, humans now lived in a number of separate world islands or zones. Within these zones, human history played out almost as if the inhabitants were living on different planets. The largest and oldest world zone was Afro-Eurasia.
