[SkyDancer]

Where did these people come from? If they’re there was the surrounding countries i.e Denmark, Norway, Sweden also inhabited then?

[Renfield]

Related:

Neolithic discovery: why Orkney is the centre of ancient Britain (Guardian,UK)

http://www.theguardian.com/science/2012/oct/06/orkney-temple-centre-ancient-britain

[JimRed]

Where did these people come from? If they’re there was the surrounding countries i.e Denmark, Norway, Sweden also inhabited then?

People most likely followed the retreating glaciers into the newly habitable lands. When sea levels rose, those in England/Scotland and Ireland were cut off until they created seaworthy watercraft.

[colorado tanker]

The main Orkneys form Scapa Flow, one of the finest natural anchorages in the world. People have been sailing to and from the Orkneys for a very long time.