2. Oak. The beginning of this layer was contemporary with the Litorina depression.
3. Scotch pine (pinus sylvestris). The earliest pines were dwarfed, the trunks showing as many as seventy rings to the inch. In upper strata their trunks were a metre or so in diameter. In the Lillemose moor, near Rudesdal, the whole eastern side, twenty metres deep, was filled with pines. While no human remains have been found in these moors, a stone axe embedded in a pine trunk, and a stone arrow-head in a bone of the bos primigenius (which, like the auerhahn or pine partridge lived on the young pine shoots) have been discovered. The soil best adapted to the pine is a damp soil, poor in humus, whereas the present rich, fertile soil of Denmark is best suited to the beech. This explains the fact that pine forests no longer grow there.
4. At the bottom, poplars and aspens. The clay underlying the pines and poplars contains leaves of arctic willows and saxifrages.
Through these types of strata we may trace the epochs described at the beginning of the chapter. The pine characterizes the Azilian-Tardenoisian-Ancylus Epoch; at the time of the Litorina depression it was fast giving place to the oak, which remains characteristic of the Neolithic and Bronze periods, yielding to the beech during the Iron Age. But this advance must have been gradual and the boundary of advance irregular.
Blytt has traced a very similar succession of changes in flora and climate in southern Norway, and Geikie in Scotland.[30] These changes are very important in our study of the traces of man’s first appearance in Denmark as furnishing not only their setting but also their chronology.
Shell-heaps are found all over the world in favorable sheltered localities where sea food is abundant, especially near clam flats. Hence they are not characteristic of any one race or time. Some are very ancient, some comparatively or very modern. They merely show the remains of the camping-grounds of people in a low stage of culture. Every one has its own history and its own slight or marked peculiarities.
The Danish shell-heaps or kitchen-middens are mounds generally about fifty metres wide and one hundred metres long, and perhaps one metre in thickness. But, as we should naturally expect, the size varies greatly according to the advantages of the situation, the number of inhabitants, and the length of time that it was inhabited.
The age of these shell-heaps is shown approximately by the presence of the auerhahn, proving the neighborhood of pine forests. The charcoal in the fireplaces came from oak wood, showing that oak forests are overspreading the country. The Baltic was more salt than at present, and the shore line was depressed. These facts indicate a period of transition from the Ancylus to the Litorina Epoch. The stone implements resemble those of western Europe during the late transition epoch, and do not occur in the oldest graves. There are no domestic animals except the dog, and no cultivated plants except some wheat in the later remains. All this seems to prove that genuine Neolithic culture had not yet reached the shores of the Baltic. They are composed mostly of oyster shells with a mingling of those of scallops, mussels, and periwinkles. The oyster has now disappeared from large parts of the coast and in others has decreased in size. Land elevation has narrowed the connection of the Baltic with the North Sea, and the water contains less salt.