02. An Introduction to the Total Work on Salt, Saltpeter and Sal Ammoniac – Salt before the Agriculture Revolution

An Introduction to the Total Work on Salt, Saltpeter and Sal Ammoniac – Salt before the Agriculture Revolution
by: Eben van Tonder
June 2018

klipgate cave
Looking out of Klipgate cave on the southern African coast.  It was occasionally occupied since 80 000 years ago.

INTRODUCTION

As a meat curing professional, my trade revolves around salt, spices, wood smoking, and drying and its application to meat in order to create exceptional dishes.  Despite not being a trained historian or archeologist, the question intrigues me how humans came to use it to preserve food and use it in foods as a condiment.

The story of salt is one of the most fascinating tales of food science.  Having studied sodium chloride, the various nitrate, and ammonia salts for many years, I intend putting it all together in more or less chronological fashion to set out for myself An Introduction to the Total Work on Salt, Saltpeter and Sal Ammoniac.  Here, I begin the work by looking at Salt before the Agriculture Revolution.

I am fortunate to have many friends from around the world who are well known and respected scientists related to various disciplines I touch on in these articles and I invite them to share their insights and make corrections in the many places where this will be necessary.

THE EARLIEST SALTING OF MEAT

The first experience of humans with cooked meat probably came when they scavenged meat that was burned by wildfires.  This would have been before we discovered how to make fire.  Such meat would have been salted by the ashes and the charcoal would have added an interesting flavour.  By eating these burned carcasses, the first experience of humans with roasted and cooked meat would have included salting which takes the earliest inclusion of salt in meat, even though not deliberately done, to a time before language even developed.  There is evidence that cooking or roasting food did not become the universal way that humans consumed meat, even long after fire was invented, (see How did Ancient Humans Preserve Food?) nor did adding extra salt to meat become a universal practice till very recently.

It is estimated that in the “5–7 million-year period since the evolutionary emergence of hominins (bipedal primates within the taxonomic tribe hominini; note that the newer term hominin supplants the previous term, hominid) ≥20 species may have existed. Similar to historically studied hunter-gatherers, there would have been no single universal diet consumed by all extinct hominin species. Rather, diets would have varied by geographic locale, climate, and specific ecologic niche.” (Cordain, L., et al.; 2005)

How likely was salt to have played a large part in their diets?  What conditions could have sparked the use of salt as a preservative and as a condiment?  Let’s see how far we can unravel the mystery.

SALT IS REQUIRED FOR SURVIVAL

Looking into the prehistoric past to try and unravel the mystery behind our use of salt, we consider our biological need for salt.  Meat, blood, and milk contain far more salt than many plants.  Nomads who subsisted on their flocks and herds or hunters who regularly ate meat did not need additional sources of salt.  Agriculturalists or nomads who for any number of reasons did not eat meat required supplementary sources of salt.

Lack of sodium is life-threatening.  “Sodium is critical for determining membrane potentials in excitable cells and participates in various metabolic reactions in the body. An adequate intake of sodium is required for optimal growth. Rats maintained on low sodium diets exhibit decreased bone and muscle weights, and required a daily intake of 300 μEq Na+ for normal growth of fat, bone, and muscle tissues. In a study conducted by Bursey and Watson “sodium restriction during gestation in rats increased the number of stillborn pups, led to smaller brain size and amount of protein per unit of wet brain tissue, and decreased total brain RNA.” Severe sodium restriction may negatively affect glucose metabolism and disturb normal blood viscosity. Distribution of intracellular and extracellular fluid volumes are dictated by sodium, and either a deficit or excess of sodium will alter overall fluid balance and distribution. Under normal circumstances, deviations from optimal body fluid homeostasis are corrected primarily by the kidneys, and proper renal handling of sodium is necessary for normal cardiovascular function.  We can say that “survival and normal mammalian development are dependent on adequate sodium intake and retention”  (Morris, M. J., et al., 2008)

“The minimum sodium requirement for humans is arguable, but it is clear that the average daily intake in developed countries far exceeds what is needed for survival. The worldwide average salt intake per individual is approximately 10 g/day, which is greater than the FDA recommended intake by about 4 g, and may exceed what is actually necessary by more than 8g.”   (Morris, M. J., et al., 2008)  A lack of sodium intake causes the onset of hyponatremia, a condition associated with sodium levels not being adequate in blood.  It is too low due to either too much water or not enough sodium intake.  This condition is characterized by nausea and vomiting, headaches, confusion, loss of energy, fatigue, restlessness, irritability and muscle weakness, spasms or cramps.

EXAMPLES OF HYPONATREMIA FROM PRIMITIVE SOCIETY

David Livingston describes that he often saw conditions in the early 1800’s on his travels in Africa, where poor people were forced to live on a vegetarian diet alone and as a result of this developed indigestion.  His comment came in the context of a reference to the Bakwains, part of the Bechuana people, who allowed rich and poor to eat from the meat hunted.  He mentions that the doctors knew what the cause of the indignation was and that it was related to a lack of salt intake. (Hyde, A., et al.; 1876: 150)

It is fascinating that Livingston describes that at two occasions later in his life, he was himself deprived of salt for months and yet, he did not have any cravings for it (Hyde, A., et al.; 1876: 150).  Interestingly enough, he reported cravings for meat and milk which he knew had enough salt to cure the onset of symptoms associated with a low salt diet.

DO WE NATURALLY CRAVE SALT IF SODIUM LEVELS ARE TOO LOW?

We have seen that we need salt, but do we know that we need it?  Do we feel “sodium deprived” and intuitively seek out salt?  We have four or possibly five taste sensors in our mouths.  Off the five, one is wholly dedicated to tasting the sodium ion, the charged atom responsible for the love of salt.  Vegetarian/ herbivore and omnivore animals are similarly equipped.  Interestingly enough, in a study on rats, it was shown that some of them naturally recognize salt deficiency as the cause for their hyponatremia.  Others had to be taught through experience.  Studies have shown and described how long-term changes in the brain as a result of hyponatremia may be behind an increased appetite for salt in animals. There is in other words, a biological reason for animals to be “directed” to salt. (De Luca Jr, L. A., Menani, J. V., Johnson, A. K. (Editors), 2014: 4)  They either crave salt when in a sodium deficient condition naturally and in some cases, it is clear that they developed the craving.

If we naturally craved salt, it would explain our love for salt and the fact that it is so dominant in our diets.  People would have naturally sought out salt deposits to amend their diets.  The facts, however, is that the salt appetite of humans does not fit the biological model.  There are great similarities between humans and other animals in how we handle sodium, but also very important differences.  The sodium ion is essential for both humans and animals and we both have special sensors dedicated to its detection.  Humans and animals share the same physiological systems that regulate it in the body, both ingest far too much of it and both show that a lack of sodium immediately following birth enhances the love of it.  But unlike animals, people do not enjoy pure salt.  Humans don’t like it in water while it has been shown that some rats prefer it.  Importantly, humans do not respond to sodium deficiency by craving for it and it never becomes a learned craving after an incident of hyponatremia.  (De Luca Jr, L. A., Menani, J. V., Johnson, A. K. (Editors), 2014: 5)

Animals who have been deprived of salt increase their salt intake robustly.  Studies in rats showed that if they have been deprived of it once, they permanently increase consumption of it but not so in humans. The dedicated sodium receptors in humans do not direct us to it when there is a deficiency in our bodies.  There are records of humans dying from hyponatremia with salt around them.  There have been many studies in humans to try and prove the opposite, but in every case, results are inconclusive at best.  The evidence is clear that unlike animals, humans will seek sodium to satisfy our pallet but not to save our lives.  (De Luca Jr, L. A., Menani, J. V., Johnson, A. K. (Editors), 2014: 5)

In humans, there is no satisfactory current explanation for the prominence of our sodium taste receptors or “for the powerful influence it exerts on our predilection for salt as the prime condiment and food additive that gives taste and tang to our food and is of no nutritional necessity.”  (De Luca Jr, L. A., Menani, J. V., Johnson, A. K. (Editors), 2014: 5)  The question comes up, why not?  There must obviously have been a time in our pre-history where we did not need this or when having it, would have been a disadvantage.

Is it that our diets in prehistoric times were varied enough and contained enough meat that we did not need to “crave” salt.  What did human nutrition look like during the stone age and in particular, 100 000 years ago when we had clear evidence of cognitive, cultured humans in southern Africa.  We can push the date even further back.  Ben Panko, writing for smithsonian.com reported on June 8, 2017, about the work of  Jean-Jacques Hublin, an anthropologist at the Max Planck Institute for Evolutionary Anthropology who studied a fossil from a cave in central Morocco. The results of their analysis of the bones revealed that humans had lived there roughly 300,000 years ago,” a 100 000 years earlier than we previously thought.  Hublin “suggest that, by 300,000 years ago, modern humans had already spread across Africa.”  (Smithsonianmag)

What did those early humans look like and what changed over the 300 000 years?

“Using advanced imaging technology to 3D scan and measure the recovered skulls, the researchers were able to create full facial reconstructions, showing a striking similarity to the appearance of humans today.  “Their face is the face of people you could meet in the street now,” Hublin told the Financial Times. “Wearing a hat they would be indistinguishable to us.”  The hat would be necessary because the major noticeable difference between these Homo sapiens and us is a differently shaped head, caused by a brain that was as large as ours, but longer and less round. Rounder brains are a major feature of modern humans, though scientists still can’t say exactly how it changed the way we think. “The story of our species in the last 300,000 years is mostly the evolution of our brain,” Hublin says.  (Smithsonianmag)

This is very important because nothing seriously could have changed over the last 10 000 years since animals have been domesticated and we began practicing agriculture, but over the last 300 000 years, a lot changed related to our brains.  Evolutionary adaptations could not have taken place since agriculture was invented to compensate for the modern food we eat but since the emergence of homo sapiens, much has changed in our make-up.

WHAT WAS THE STONE AGE DIET?

There are several ways that we can look back into our ancient past and try and unravel what our food looked like.

John D. Speth (2017) makes a compelling case for the earliest meat humans ate to have been putrid and fermented.  Another method of identifying what we are in the stone age is suggested by Cordain et al (2005) with their concept of evolutionary discordance theory.   According to them, contemporary chronic diseases and health issues are partially, if not largely, due to an evolutionary “clashing” with new patterns introduced in our modern world after the agricultural revolution approximately 10 000 years ago when agriculture and animal husbandry was developed.

Cordain, et al, explains it as follows.  They say that “contemporary humans are genetically adapted to the environment of their ancestors—that is, to the environment that their ancestors survived in and that consequently conditioned their genetic makeup. There is growing awareness that the profound environmental changes (eg, in diet and other lifestyle conditions) that began with the introduction of agriculture and animal husbandry ≈10 000 y ago occurred too recently on an evolutionary time-scale for the human genome to adapt. In conjunction with this discordance between our ancient, genetically determined biology and the nutritional, cultural, and activity patterns in contemporary Western populations, many of the so-called diseases of civilization have emerged.

An example is Cordain et al’s case is that refined sugar consumption increased since 500 BC and high-fructose corn syrup since the 1970s which may have caused discordance. “Lacking evidence directly associated with hominin diets, it is left unknown how simple sugars may have actually shaped evolution of hominins.

The data, however, on ape diets suggests a fruitarian ancestry governed by plants. Although the sugars of these fruits are evidenced to have been accompanied by diverse dietary fiber sources, nutritional variations may have occurred not unlike refined sugars and large amounts of fructose. It is also unclear why fructose, heavily associated with diabetes, should be prevalent in the main foods of a hominin ancestral diet.

Science must ultimately make up perceptions on a factual matter regarding nutrition and medicine where historical and archeological evidence fall short and can only present clues.

Double-blind, randomized cross-over designed trials on each discordance—cereals, refined sugars, refined vegetable oils, alcohol, salt, fatty domestic meats, etc.—and how differing amounts affect health must be researched for proper nutritional determinations.

For example, two interventions over a year’s time could be performed in which one group could be given wild-caught salmon and deer meat and the placebo group would receive farmed salmon and deer meat. Blood lipids and abdominal fat stores can be measured throughout the year.

Because of possible interplay from each discordance that should not be discounted, double-blind randomized cross-over trials should also include versions of whole, supposed Paleolithic diets.

Each study performed, in turn, may also offer revelations into evolutionary past. And perhaps, to make things more interesting, the studies should also be performed on bonobos and chimpanzees.”  (David Despain.  Evolvinghealthscience)

What we can say for sure from the work of Speth (2017) and Cordain et al. (2005), is that before the development of agriculture and animal husbandry, hominin dietary choices would have been necessarily limited to minimally processed, wild plant and animal foods.  If the meat was not fresh, it would have been putrid and fermented and minimally cooked or warmed.  Salt could have played a role in hominin and more particularly, early homo sapien diets if we too had a natural craving for salt like other animals which we lost.  If this was the case, however, one would expect to see evidence of salt mining around the time when we know for sure that cognitive, cultured humans existed.  Such a time and location is 100 000 years ago in southern Africa.  Despite vast natural salt resources in salt pans and salt springs in the region, there is no evidence that any of this was ever mined or that communities sprang up around the salt resources to exploit it till well into the 1800’s.

Cordain et al. (2005) state it as follows. “It is likely that Paleolithic (the old stone age which began 2.6 million years ago and ended 10 000–12 000 y ago) or Holocene (10 000 y ago to the present) hunter-gatherers living in coastal areas may have dipped food in seawater or used dried seawater salt in a manner similar to nearly all Polynesian societies at the time of European contact. However, the inland living Maori of New Zealand lost the salt habit, and the most recently studied inland hunter-gatherers add no or little salt to their food on a daily basis. Furthermore, there is no evidence that Paleolithic people undertook salt extraction or took interest in inland salt deposits. Collectively, this evidence suggests that the high salt consumption (≈10 g/d) in Western societies has minimal or no evolutionary precedent in hominin species before the Neolithic period.” (Cordain, L. et al; 2005)

BUILDING UP A SUBSTANTIAL BODY OF KNOWLEDGE ABOUT SALT FROM VERY EARLY

Humans would not have naturally gravitated towards additional sodium intake besides what is found as a constituent of our food and the remedy to hyponatremia.  What possible scenarios could have existed that lead to humans “discovering” its nutritional value and as that it acts as a preservative.  It is easy to imagine how early humans would have seen animals licking salt and how they would have mimicked the behaviour even in the absence of a natural craving for sodium.  The fact that salt cures hyponatremia and its link to an exclusively vegetarian diet is also something that early humans would have discovered.  One can then imagine how vegetarians would have developed it and people who eat meat did not.  It would have been clear.  It is also easy to see how salt could have been ingested by some of the people who only relied on a plant-based diet and the symptoms would have disappeared.

I focus on what happened 100 000 years ago in Africa since it is here where we find the oldest evidence of cognitive and cultured human beings dating to this time in southern Africa.  Whether the link with salt was made 100 000 years ago did not depend on the cognitive ability for people to recognize it, but the question should be that by what date would one encounter people with a vegetable diet only; where in the world was it most likely to find such societies and how likely would it have been for them to have access to salt and to have discovered that salt resolves hyponatremia.  This relates to the nutritional aspect of salt.

On the other hand is the questions “when” and “where” was it most likely to have discovered the preserving power of salt in meat and by extension, the power of sal ammoniac and saltpeter salt in meat preservation.  What conditions would favour these discoveries which will help us identify the “where” and “when”.   I venture some guesses.  There can be little doubt that putrified meat and fermentation predates salt preservation.  (How did Ancient Humans Preserve Food?)  Ancients would have noticed the preserving power of simply submerging the carcass in water and storing it there for future consumption.  They would have observed this from animals which drowned in bodies of water.  There is little doubt that such carcasses, retrieved from salt water would have been different in terms of taste and preservation.

Interesting components are coming together in such a scenario which surely would have lead to the discovery of its preserving powers by simple observation namely salt water (brine), dead animals, noticing its state of decomposition relative to animals retrieved from freshwater and cognitive, cultured humans who were able to make these links from events separated by time and space.  We know that all these were present in southern Africa from at least as early as 100 000 years ago which means we can speculate that some knowledge of salts could have started to come into human culture by this time.  As individuals started to observe this, it was now up to the modes of dissemination and its speed by which it was related from group to group that would have become important.  It is interesting that there is no evidence of salt mining in southern Africa till much later.

Similar to animals drowning in water and carcasses deliberately being stored under water as one of the oldest forms of meat preservation, is the fact that animals which died in desert areas where the wind blew salt-sand onto the carcass must have equally been subjected to a different rate of decomposition compared to freshly killed animals, untreated by salt or water immersion.  It is this which I believed played a crucial role in discovering nitrate curing in the Turfan area where, by the early Bronze age, bodies were subjected to natural mummification, partly as a result of nitrate-rich sand blowing over them.  Thinking about it makes it clear that examples of natural salt preservation must have been all around early humans to observe.  The question is really, which hominin species was able to make the connection cognitively and in the case of southern Africa, why was it never developed any further.  It is safe to say that salt preservation never played any part in the indigenous cultures in southern Africa.

There must have been a considerable time between the discovery of the value of salt and when it became part of popular culture.  Ons of the big reasons for this was availability.  We can identify when this happened by identifying when mining of salt emerged.  Mining it would necessarily have been preceded by discovering its value which then created a demand and which, in turn, lead to its mining.

The next article will feature some stone-age chemistry as we look at the analytical techniques that were required to start separating out different kinds of salt.  We also look at the oldest salt mines on earth to start forming a picture of where cultures emerged, based on this unique mineral.

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References.

Brigand, R., Weller, O. (Editors).  2015.  Archeology of Salt.  Sidestone Press

Cordain, L., Eaton, S. B.,  Sebastian, A., Mann, N., Lindeberg, S., Watkins, B. A., O’Keefe, J. H., Brand-Miller, J.; Origins and evolution of the Western diet: health implications for the 21st century, The American Journal of Clinical Nutrition, Volume 81, Issue 2, 1 February 2005, Pages 341–354, https://doi.org/10.1093/ajcn.81.2.341

De Luca Jr, L. A., Menani, J. V., Johnson, A. K. (Editors).  2014.  Neurobiology of Body Fluid Homeostasis: Transduction and Integration.  CRC Press.

Engelbrecht, J. A..  1936.  The Korana.  Maskew Miller, Ltd..  Cape Town.

http://evolvinghealthscience.blogspot.com/2009/06/evolutionary-discordance.html

Iziko South African Museum (South African’s national museum located in Cape Town

Henshilwood, C.S. & Marean, C.W. 2003. The origin of modern human behaviour: A review and critique of models and test implications. Current Anthropology 44 (5): 627-651
Hyde, A., Bliss, F. C., Tyler, J..  1876.    The Life and Life-work of Dr. David Livingstone.  Columbian Book Company.

Mitchell, P., Lane, P. (Ed’s).  2013.  The Oxford Handbook of African Archaeology.  Oxford University Press.

Morris, M. J., Na, E. S., & Johnson, A. K. (2008). Salt craving: The psychobiology of pathogenic sodium intake. Physiology & Behavior94(5), 709–721. http://doi.org/10.1016/j.physbeh.2008.04.008

Needham, J.  1980. Science and Civilisation in China, Volume 5.  Chemistry and Chemical Technology.  Cambridge University Press.

Schlebusch CM, Malmström H, Günther T, Sjödin P, Coutinho A, Edlund H, Munters AR, Vicente M, Steyn M, Soodyall H, Lombard M, Jakobsson M.  2017.  Southern African ancient genomes estimate modern human divergence to 350,000 to 260,000 years ago.  Science. 2017 11 03358(6363):652-655

https://www.smithsonianmag.com/science-nature/humans-evolved-100000-years-earlier-we-thought-180963619/

Photo Credit:

Klipgat Cave – eben van tonder

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