Population centres and edges

The steady migration of people to all parts of the western world, north and southeast Asia, Australia and the New World between 30 ky and 90 ky was probably a product of increasing pressures from a slowly growing world population. Small incremental improvements in implement manufacturing, planning and strategy building, economic diversification and cultural modification helped these movements. People were now being soaked up in marginal regions, including high latitude and semi-arid environments, which enhanced the migration process, enabling them to enter regions not previously explored and the use of watercraft culminated in island hopping and the comparatively quick spread of people into island southeast Asia and Australia. Moreover, amelioration of environmental and weather conditions during interglacials opened up vast new areas for occupation and to explore, although, with the rise in sea level, continental shelf space was reduced. Migration was not an imperative, but a hunter-gatherer way of life required space, so migration and exploration went hand in hand. A small push here, a foray there and valleys, rivers, deserts and steppe country gradually became home to many. In empty territory, migrants entered in slow trickles not bow waves; they did not fan out but penetrated in rivulets. It is difficult, however, for people living in a world that has been populated for some time to move to an area where others do not already live.