RODENTS REWRITING HISTORY

DNA analysis of island-dwelling voles and mice is revealing startling secrets about our ancient past

- JON DUNN

NORTH OF THE British mainland, there's a mystery hiding beneath the short grass and wildflowers of the Orkney Isles. Within sight of the magnificent remains of the Neolithic settlements of Skara Brae and the Ness of Brodgar, and in the shadow of the brooding Ring of Brodgar and Stenness standing stones, this mystery is living history, complete with whiskers, glittering black eyes, and a pedigree quite unlike any other resident British mammal. It's the Orkney vole.

Voles are found all over the British Isles. But while those on mainland Britain are field voles (Microtus agrestis), those on Orkney are actually common voles (Microtus arvalis).

Common voles are, as their name suggests, common throughout mainland Europe, but entirely absent from Britain - apart from on those low-lying islands of Orkney. So the question is: what on Earth are they doing there? 

Those Orkney voles have a tale to tell, if only they could talk and share their history with us. But science is giving us an insight into their secret past. While every summer sees archaeologists descend on the islands to uncover a little more of the human history buried there, archaeology of a very different kind is unlocking some chapters in the rodent's story, using not only trowels, brushes and sieves, but studies of DNA.

The presence of common voles on Orkney has been an enduring puzzle. How could these rodents possibly be there and there alone, and in such numbers? Current estimates place their population somewhere in the region of a million individuals.

More intriguing still, those digging, scraping and sieving archaeologists have found thousands of vole bones and teeth in Neolithic dwellings, dating between 3,4553,100 BCE. While this discovery confirms that voles have been present in Orkney for thousands of years, it still leaves the conundrum of how they physically arrived on the islands.