The Neolithic in Scotland is regarded as beginning ca. 4000 BC and marks the beginning of farming, initially perhaps to supplement a hunter-gatherer economy, possibly during a period of pressure on resources or perhaps for cultural reason associated with status, the possession of cattle for example. Environmentally it can be detected by changes in the pollen record. Tree species decline in favour of plants of open or disturbed ground, notably ribwort plantain and cereal pollen.
The Neolithic is an important period to archaeologists because it is arguably the first time that we have evidence for particular groups of people beginning to see themselves as special or different in some way from the world they inhabit. They began to substantially modify their environment clearing woodland, enclosing the landscape and erecting permanent built structures. It is possible that they came to understand their world in new ways, and it would seem that the manifestation of abstract concepts in physical form became an important part of their culture.
We also see a change in the material culture, in particular ceramics and polished stone objects, some prosaic and others whose purpose and meaning we do not yet understand. Round bottomed bowls are seen as diagnostic for the early Neolithic.
The character of the Neolithic stone tool industry is markedly different from the preceding Mesolithic. The blade-based microlithic industry was displaced by a flake-based technology, the flakes being broader and shorter than blades. A single leaf-shaped arrowhead, diagnostic of the Neolithic period, displaced the microlithic compound arrow tip of the Mesolithic.
The polished stone axe was a further important innovation. Made from fine-grained igneous rock, it provided a more efficient means of felling trees than the chipped flint axe and was widely traded. Many fine examples have clearly never been use as implements and appear to have been made purely as high status gifts or for ritual deposition (10).
The houses of Neolithic people are difficult to find in mainland Scotland and none have been found in Caithness. Nevertheless the Neolithic period is well represented at Yarrows, and is recognised both from lithics collected during field-walking and from Neolithic material recovered from chambered cairns
Radiocarbon dates from chambered cairns suggest that the oldest cairns were built during the early 4th millennium BC. Archaeologists classify chambered cairns into groups sharing common features, forms of chamber and entrance for example. There is a degree of regional and local variation in their general form. The Caithness cairns belong to the Orkney-Cromarty group of passage graves (6). Within this general categorisation there remains a degree of variation. Cairns may be long, short or round, plain or horned and the chambers may be single, bipartite, tripartite or stalled, indicative of change in style over time and perhaps between different groups of people.
At Yarrows there are five long and four round known cairns, three of which are now largely destroyed. The in Caithness round cairns are generally thought to be earlier than the long form and there is evidence to suggest that existing round cairns were converted into the long form. In southern Britain however long barrows (an earthen version of a stone cairn) are seen as early.
The cairn was not just an arbitrary embellishment for the burial chamber; it was a necessary component of the monument, the weight of which prevented the collapse of the corbelled roof of the chamber. In short at all points on the oversailed section, the weight of the corbelling oversail must be counterbalanced by an equal or greater weight of cairn material (7). Neither was the cairn just a random pile of stone as they now appear, but was a built construction having two elements, a core cairn necessary to prevent corbel collapse, and an architectural element that expressed the aesthetic choices of the builders, facades and horns for example. The detail of construction of one such long horned cairn at Point of Cott, Orkney was revealed by total excavation (8).
At Point of Cott, a strong well-built core cairn was constructed to house the entrance passage and chamber. The long tail of the cairn was constructed separately, using a two-tier box like space-filling structure that was much less well built than the core cairn saving on effort and material. Finally the separately built core cairn and long tail were enclosed by concentric layers of walling (onion-skin walls) to unify the monument and add the facade, horns and any other architectural features that are not essential to the structural integrity of the monument (8). The images entitled model 1 and model 2, accessible at node 0, illustrate the construction method.
There is much interest in the choice of site for the chambered cairns in relation to possible areas of settlement. Although six of the nine cairns at Yarrows were built on high ground and probably overlooked the settled areas, three cairns were built on low ground probably close to where people lived.