On remote islands north of Scotland, sheep eat seaweed. The normally finicky ovines have been doing so for about 5,500 years at Skara Brae, an ancient settlement in the Orkneys, archaeologists have now proved.
Moreover, the sheep even underwent metabolic evolution to tolerate the aquatic plants so alien to their normal sustenance, and to thrive on them. But they don’t seem to have developed a taste for it.
Given their druthers, sheep do not eat seaweed unless they have a salt craving. But at least sometimes the animals living in coastal northern Europe and the Orkney Islands, where they arrived in around 3,500 B.C.E., didn’t have much choice, explains Marie Balasse of the French National Centre for Scientific Research, with Anne Tresset, Gaël Obein and Denis Fiorillo, in the Antiquity journal.
Balasse adds that salt-deprived ruminants who have access to shoreline do indeed spontaneously eat seaweed. But the thing is, when sheep first arrived in the windswept Orkneys over 5,000 years ago, if they didn’t get used to a seaweed diet they would have starved. Seaweed was key to enabling animal husbandry at all there, the archaeologists posit.
In fact, not only there. Animal feed was augmented with seaweed along coastal northwestern Europe, where, like in the hardscrabble Orkneys, grazing animals was usually not an option.
The study of the prehistoric animals’ diet at Skara Brae is based on analysis of carbon isotopes in their teeth. Radiocarbon dating of organic remains in the village dates the start of its occupation to 3180 B.C.E.
The rediscovery of Skara Brae
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Skara Brae is a Neolithic site on the coast of the Orkneys’ main island, but back when sheep arrived the village had been inland. The stone houses, complete with their stone furniture — erected thousands of years before Stonehenge in southern England — were rediscovered in 1850 when a storm powerful enough to strip soil from the hills howled into Scotland. When the skies cleared and the locals ventured outside, they saw the remains of the long-lost village.
The brick houses had been built sunken into the ground and were therefore protected from the elements, resulting in one of the best-preserved Neolithic villages anywhere in Europe.
In fact, Skara Brae was part of a Neolithic culture spread throughout the British Isles, which was evidently in touch with Neolithic Europe and possibly beyond. Also, while Skara Brae itself presently consists of eight buildings, it was apparently bigger back in the day (featuring at least 10 buildings, as one archaeologist observed to Haaretz).
Cattle and sheep apparently began to reach southern England around 6,000 years ago, around five millennia after the domestication of the mouflon in Mesopotamia. It would take about 500 more years for sheep to reach Scotland and its storm-battered isles.
The sheep brought to the northern Scottish islands weren’t European-type, Balasse tells Haaretz: To this day they retain primitive characteristics of the origin species, the mouflon.
Genetics and morphology place the Orkney sheep closer to the sheep that accompanied Neolithic migrants from the Near East. They are less like modern mainland European sheep, which mixed with later migratory waves of ovines, Balasse tells Haaretz.
Crucial to the Neolithic expansion was adaptation to new environmental settings and pasture resources, Balasse and the team write. So if they were to live by a far-northern chilly coast, they had to learn to eat what was there. At least, the animals had to.
Asked whether the Neolithic people of Skara Brae likely also ate seaweed (a la prehistoric sushi, perhaps), Balasse says there is no evidence for that. “For sure, seaweed as a diet was not badly considered, as it was given to the sheep, which were eventually eaten by people,” she qualifies. “They might also have used seaweed to fertilize the cultivated soils.”
A diet of arsenic
Goats aren’t fussy. Sheep are, which is one reason the ancients of the Levant tended to prefer the goat. Goats will eat anything, more or less. Sheep prefer to eat forbs — which are flowering, non-grassy plants — and grass. They are also happy to eat grain. In modern industrial husbandry, sheep are also fed agricultural by-products such as peanut hulls. It does not seem that sheep are happy to eat seaweed.
However, sheep will evidently expand their dietary range when the circumstances demand it. In other words, starving sheep will eat anything. There are reports of sheep eating chicks, adult birds and even each other. In 2002, Niall Burton of the British Trust for Ornithology disgustedly reported watching sheep gulp down grouse chicks, not by accident, and points to earlier scholarly work on ovine carnivory.
The Orkneys and Skara Brae are the same latitude as southern Scandinavia, but the climate is temperate thanks to the warming effect of the Gulf Stream. So there is grass, which the sheep like a lot, when it can be found. But there are few trees, hence no leaves to feed to ruminants when pasture is scarce, as was done in much of Neolithic Europe.
Agriculture on the islands is constrained by the acidic soil, but the inhabitants of Skara Brae did manage to grow black oats and bere barley, the latter possibly introduced to the region by the Vikings. The people shared these grains with their beasts, but seaweed was more convenient.
It still is. The sheep of the Orkney coasts still eat seaweed. But there are issues with a seaweed-based diet, one being the high concentration of arsenic in the oceanic plant.
Fortunately for them, or for the islanders, tests on Orkney sheep that still consume seaweed compared with sheep that eat grass suggest the island animals adapted to tolerate high arsenic concentrations in their food (as reported in 2000 and 2003).
Isotope analysis indicates that the very first sheep who reached Papa Westray island in the Orkneys in the fourth millennium B.C.E., specifically a site called Knap of Howar, did not eat seaweed. But 500 years later, sheep elsewhere on Papa Westray, at a site called Holm of Papa Westray, were eating seaweed, albeit mostly in winter.
(Knap of Howar is better known for housing the oldest preserved stone house in northern Europe, occupied from around 5,700 years ago. It’s about 300 years older than Skara Brae.)
Plausibly, the sheep at Holm simply had no choice and ate seaweed even if it made them sick, and over time their arsenic metabolism adapted, enabling them to eat large amount of seaweed without harm.
Cows at Skara Brae were not fed seaweed, or at least wouldn't eat it, Balasse observes. Probably the villagers would have tried.
But possibly an ever knottier obstacle to a seaweed regime is sugar metabolism.
“The challenge is in the sugars,” Balasse explains. “In land plants, the sugars are cellulose and lignin. Seaweed has other very specific polysaccharides instead. If it becomes a major component in diet, the digestive system, the rumen bacteria, have to adapt.”
Anyway, the sheep of the Orkneys eat seaweed to this day and on North Ronaldsay, the northernmost island of the Orkneys, they eat nothing else — because they can’t. The sheep are confined to the shore area. Where the dike breaks and the sheep can reach grass, they do and they eat it, which shores up the postulation that they don’t actually like seaweed.
About 600 years after its first occupation, Skara Brae was abandoned. Why is anybody’s guess.
The first archaeologist to investigate the site, starting in 1927, was an Australian named Vere Gordon Childe from the University of Edinburgh. He evocatively described evidence of sudden flight. “As was the case at Pompeii, the inhabitants seem to have been taken by surprise and fled in haste, for many of their prized possessions, such as necklaces made from animal teeth and bone, or pins of walrus ivory, were left behind,” he wrote.
In this case, though, they wouldn’t have been escaping an exploding volcano but more likely an Atlantic howler. Childe claimed that the people even left food in their stone beds, a telling sign of panicky flight. Or maybe they just didn’t like it.