Early in Orcadia was first published in 1987, and consists of five stories, set hundreds of years apart in time and dealing with different characters, but connected by their location in a particular corner of Orkney during the period known as the Stone Age. Mitchison links them formally by interpolating passages of fact and explanation between the fictional episodes, and by speculating in her own voice about what happened in prehistory, as far as it can be known from archaeological research, and how it fits in with the world of today.

The slightly awkward jumps from one story to the next indicate that the development of the human race was not a completely smooth and seamless process. There must have been significant moments when a highly important discovery or invention took place. The structure of the book is demonstrating its theme - that there are sudden advances but just one story running from the earliest times to the present day, and it is the story of humankind. From the Introduction.