pleistocene megafauna along ice-free corridors that stretched between the Laurentide and Cordilleran ice sheets. Another route proposed is that, either on foot or using primitive boats, they migrated down the Pacific coast to South America as far as Chile. Any archaeological evidence of coastal occupation during the last Ice Age would now have been covered by the sea level rise, up to a hundred metres since then. The recent finding of indigenous Australasian genetic markers in Amazonia supports that a coastal route and subsequent isolation did occur with some migrants. Holocene migrations The Holocene is taken to begin 12,000 years ago, after the end of the Last Glacial Maximum. During the Holocene climatic optimum, beginning about 9,000 years ago, human populations which had been geographically confined to refugia began to migrate. By this time, most parts of the globe had been settled by H. sapiens; however, large areas that had been covered by glaciers were now re-populated. This period sees the transition from the Mesolithic to the Neolithic stage throughout the temperate zone. The Neolithic subsequently gives way to the Bronze Age in Old World cultures and the gradual emergence of the historical record in the Near East and China beginning around 4,000 years ago. Large-scale migrations of the Mesolithic to Neolithic era are thought to have given rise to the pre-modern distribution of the world's major language families such as the Niger-Congo, Nilo-Saharan, Afro-Asiatic, Uralic, Sino-Tibetan or Indo-European phyla. The speculative Nostratic theory postulates the derivation of the major language families of Eurasia (excluding Sino-Tibetan) from a single proto-language spoken at the beginning of the Holocene period. Eurasia Evidence published in 2014 from genome analysis of ancient human remains suggests that the modern native populations of Europe largely descend from three distinct lineages: "Western Hunter-Gatherers", derivative of the Cro-Magnon population of Europe, Early European Farmers introduced to Europe from the Near East during the Neolithic Revolution and Ancient North Eurasians which expanded to Europe in the context of the Indo-European expansion. The Ancient North Eurasian component was introduced to Western Europe by people related to the Yamnaya culture. Additional ANE ancestry is found in European populations through Paleolithic interactions with Eastern Hunter-Gatherers. Sub-Saharan Africa West-Eurasian back-migrations started in the early Holocene or already earlier in the Paleolithic period (30-15kya),followed by pre-Neolithic and Neolithic migration events from the Middle East, mostly affecting Northern Africa, the Horn of Africa, and wider