stayed became hunter-gatherers of the forests and fishers of the numerous bays, inlets and shallow waters around the thousands of islands that now spangled the seas of Europe. They lived richly and were encouraged to enter the pre-productive phase that we call the Mesolithic. Those who moved east hunted out the last of wild big game and turned their best efforts into learning to herd what was left. In the Americas, humans had left the Paleoindian phase and were now in the Archaic. Meanwhile humanity toward the south of the north temperate zone had already turned to food production in a number of widely separated locations and were on the brink of civilization. There is no evidence of any extensive contact with the cultures of the north during the Boreal. The producers tended to live in dense centers without any interest in moving from there except when motivated to find new lands. The gatherers ranged widely over their lands, building only temporary settlements in which to spend the winter. Flora During the Pre-Boreal pollen zone IV, large quantities of tree pollen began to replace the pollen of open-land species, as the most mobile and flexible arboreal species colonized their way northward, replacing the ice-age tundra plants. Foremost among them were the birches, Betula pubescens and Betula pendula, accompanied by Sorbus aucuparia and quaking aspen, Populus tremula. Especially sensitive to temperature changes and moving northward almost immediately were Juniperus nana and J. communis, the dwarf and shrub juniper respectively, which reached a maximum density in the Pre-Boreal, before their niches were shaded out. Pine soon followed, for which reason the resulting open woodland is often called a birch or a pine-birch forest. In the yet warmer early Boreal pollen zone V, Corylus avellana (hazel) and pine expanded into the birch woodlands to such a degree that palynologists refer to the resulting ecology as the hazel-pine forest. In the late Boreal it was supplanted by the spread of a deciduous forest called the mixed-oak forest. Pine, birch and hazel were reduced in favor of Quercus, Ulmus, Tilia and Alnus. The former tundra was now closed by a canopy of dense forest. In the marshland Typha latifolia prevailed. Less cold-tolerant species such as ivy and mistletoe were to be found in Denmark. Fauna The new forest was populated with animals from refugia in Italy, Spain and the Balkans. Animals such as Emys orbicularis