The Mesolithic - c9000-4000BC

Compared to the wealth of material for later periods of prehistory, the evidence of the human inhabitants of Orkney during the Mesolithic period is scant.

The people of the Mesolithic were nomadic hunter-gatherers, living in small groups and shifting according the season and the availability of food supplies.

This, along with the fact that they did not leave stone constructions such as Skara Brae or Maeshowe, means that they have left little trace for the modern archaeologist.

Although we know that these wandering hunters crossed from Scotland into Orkney, it is not clear when. The first settlers in Scotland arrived after the Ice Age, drifting in around 7,000 BC, some time after the ice sheets had retreated north and the climate improved.

At this time the wooded landscape of Orkney would have been unrecognisable to modern Orcadians. The sea-level was considerably lower - up to 30 metres lower - so today's green, rolling Orkney hills would have been the peaks of high ground.

What these early hunters would have regarded as lowland is now many metres under water - a fact that goes some way to explains the lack of archaeological evidence.

Whenever they arrived in Orkney, it is doubtful that they settled long.

Their survival depended on hunting and gathering food, so when one supply ran out they moved elsewhere. As a result, they left no tangible buildings or objects, other than a handful of stone flakes, as evidence of their movement.

Instead, they existed much as the nomadic cultures of the world still do today - living in temporary shelters that could be easily dismantled and transported between sites.

They lived off the land, gathering roots, berries and shellfish and hunting the birds and animals in a land recently emerging from an icy sleep.