How new archaeological discovery in Yorkshire could rewrite British prehistory

Exclusive: Excavation reveals a 5,750-year-old salty Yorkshire tale – with big implications, reports David Keys

Archaeologists, near Loftus, Yorkshire, excavating western Europe’s earliest known salt-manufacturing complex (Stephen Sherlock)

Archaeologists working on the Yorkshire coast have unearthed the oldest salt-making complex ever found in western Europe, in a discovery that is set to revolutionise our understanding of prehistoric Britain’s economy.

Dating back almost 6,000 years, the site – complete with salt-making kilns, or hearths – predates the oldest previously known British salt ‘factory’ by almost 2,400 years.

The discovery has huge implications for our understanding of how Neolithic Britain’s economy functioned – and suggests that it was far bigger and more efficient than previously thought.

The economy was based substantially on cattle – without salt, however, efficiently operating such an economy would have been impossible.

The discovery in Yorkshire therefore suggests that Britain’s earliest agriculturalists were able to produce much more food than was previously considered to be the case – and that that would have enabled more rapid population expansion, thus accelerating social and political change.

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The discovery also has substantial implications for prehistorians’ understanding of the nature of early trading activity in Britain.

The archaeologists – excavating near Loftus, Yorkshire – have so far discovered three salt-making kilns and fragments of dozens of ceramic bowls used in the process.

Scientific tests on those fragments have shown very high levels of salt on their interior surfaces.

“This discovery changes our understanding of key aspects of the Neolithic economy,” said the director of the excavation, Dr Stephen Sherlock, an archaeologist working for Highways England.

The new discovery suggests the crucial role that Boulby Cliffs played in the economy of Neolithic Britain (Tony Bartholomew)

“In Britain, it pushes back salt-making, an extremely important industrial process, by almost 2,400 years,” he said.

There are no sources of rock salt in the Yorkshire area (and, in any case, rock-salt extraction would not have required kilns), so the salt was almost certainly being made from sea water.

The process probably had two stages: first, the Neolithic salt makers would have had to turn sea water into brine through natural evaporation, achieved through exposure to wind and sometimes the warmth of the sun; second, they would then have used kilns or hearths to turn the brine into salt crystals.

The initial process of turning salt water into brine would have involved using wide, shallow pans, probably clay-lined depressions, near the seashore – or on the clifftop near the kilns.

“Extracting salt from seawater is a time-consuming and complex operation, requiring considerable skill. Any ancient coastal culture that was able to master that technology would have been able to expand their economy substantially,” said one of Britain’s top authorities on sea-salt production, David Lea-Wilson, who runs a traditional sea-salt extraction operation, Halen Mon, in Anglesey, north Wales.

The discovery that Neolithic people had the technology to make salt has major implications for the modern world’s understanding of how Britain’s early agricultural economy functioned.

Salt would have enabled Neolithic people to very substantially increase their beef and dairy production – by making it possible for them to properly preserve meat.

Without salt, they would have been unable to efficiently manage their cattle assets – the basis of much of their economy.

Half of newborn calves would inevitably have been male – and therefore had only limited economic value. As well as not being able to produce milk for dairy production, their testosterone levels would have given their meat an unpleasant taste after their first year of life. In addition, if allowed to grow into adulthood, they would have been very difficult to control, and would have unproductively consumed pasture and required the provision of additional winter fodder.

It would therefore have been much more efficient to cull most male cattle before, or when, they completed their first year of life. But without salt, there was no way of fully preserving the meat (because smoking is much less efficient – and Britain and most of northern Europe is too humid for drying in air).

The newly discovered fact that salt was available would therefore have revolutionised early agriculture by enabling the meat from slaughtered young male cattle to be preserved and used as a continuous year-round food source, and also freeing up pasture for milk-producing female cattle, boosting dairy yields as a result. It would also have reduced the quantities of winter fodder required. A year-round supply of salt-preserved meat would also have removed the necessity to slaughter many milk-producing female cattle – and that would have further increased milk supplies and any yoghurt, cheese and butter production.

“Without salt, it would have been virtually impossible for these early agriculturalists to properly preserve their beef in the damp British climate,” said James Swift, a leading authority on traditional meat preservation technologies, who runs one of the UK’s longest-established traditional meat-curing operations, Trealy Farm Charcuterie, in Monmouthshire.

What’s more, salt was easy to trade and transport. The discovery that Neolithic Britons were able to mass-produce salt therefore has substantial implications for the expansion of trade – and the ability of inland peoples to also acquire salt and, in turn, preserve their meat stocks.

The newly discovered Yorkshire salt-making kilns were built in about 3,750 BC – approximately 750 metres from the top of a 200-metre high cliff overlooking the North Sea.

The location of the salt works was probably determined by the availability of timber that could be burned to heat the kilns – and by the water-evaporation-inducing wind speeds (sometimes more than 70mph) near the cliff edge. The site is arguably one of the most ideal locations in Britain for salt production because the coastal topography at that point (known as Boulby Cliffs, part of the North York Moors National Park) is higher and windier than anywhere else along England’s east and south coasts; indeed, they are almost twice as high as the white cliffs of Dover.

It is conceivable that the first stage in production (turning seawater into brine) was carried out near the seashore – but the sea was a one and a half mile walk away, down a winding valley path. It is perhaps more likely therefore that ropes and animal-skin bags were used to lift large quantities of seawater to the clifftop, where the higher wind strengths would have dramatically accelerated any salt-pan evaporation process needed to turn the seawater into a denser briny liquid, suitable for final drying in the kilns.

Today the cliff edge is 200 metres nearer the kilns than it would have been in Neolithic times; in that area, an average of seven metres (about 125,000 cubic metres of rock per 100 metres of cliff) is being eroded by the North Sea every century.

The dating of the newly discovered Neolithic salt works was carried out by the Scottish Universities Environmental Research Centre, an institution administered by Glasgow University, while the scientific analysis of the salt residues on the ceramic containers used in the kilns, or hearths, was carried out by the University of Sheffield. The discoveries at the site are being published today in the UK-based archaeology journal Antiquity. Not only is the site the oldest salt-making complex in Britain, but it is also the oldest known in western Europe by several hundred years.