The resilient seaweed-eating sheep of the Orkneys
Farming became established on some inhospitable islands after animals adapted their diet. Barry Keily reports.
Whether it’s a credit to the adaptability of early farmers or the animals they farmed remains to be determined, but new research has found that settlers on the remote Scottish Orkney islands would likely have perished had not their sheep quickly developed an appetite for seaweed.
The Orkneys are cold, windswept, storm-tossed, and lie 290 kilometres distant from the northernmost tip of Scotland.
Summers are short and winters are long, and although comparatively little snow falls each year, the temperatures and high winds combine to produce a plant ecosystem dominated by low-lying and seasonal species.
The practice of cattle and sheep farming began in Britain around 4000 BCE, introduced from Europe. From an initial base in the southeast it spread across the island – and eventually off it, reaching the Orkneys around 3500 BCE.
Upon arrival, however, the hopeful farmers and their charges faced a substantial challenge. Plant feedstock was in adequate supply during the warmer months, but fell right away during the rest of the year.
However, according to research led by archaeobiologist Marie Balasse, from the Centre National de la Recherche Scientifique (CNRS) in Paris, the newly arrived sheep were quick to exploit another, much more abundant source of nutrients.
“The results show that sheep consumed moderate amounts of seaweed from the moment of their introduction to Orkney – a practice that facilitated the successful spread of the farming lifeways to the most remote areas of Europe,” she and colleagues write in a paper published in the journal Antiquity.
To make their findings, they measured stable carbon isotope ratios in the teeth of several sheep skeletons from the ancient settlement known as Skara Brae.
The ratios varied on a regular basis, indicating seasonal changes in diet for the animals, and correlated with the isotope ratios found in seaweed and terrestrial plants.
The results showed that the animals had started eating seaweed very soon after their arrival from the mainland, and that by 2500 BCE it had become “established practice”.
The unusual diet, the researchers suggest, may well have driven changes in the behaviour and physiology of the sheep of Skara Brae. Just how the new food regime developed, however, for the moment remains an open question.
“It is not possible to establish whether Neolithic sheep turned to seaweed of their own accord or were brought to the shore by herders,” the researchers note.