Researchers have long claimed that the nutritional benefits of chickpeas could be one of the reasons for the rise of civilization in the fertile crescent of Mesopotamia, now a team of Israeli scientists believe they have discovered the reason why.
Zohar Kerem and Shahar Abbo from the Hebrew University of Jerusalem have found that cultivated chickpeas contain three times as much amino acid tryptophan, a precursor of the neurotransmitter serotin, as wild chickpeas.
Tryptophan is responsible for brain serotonin synthesis, which in turn affects certain brain functions and human behaviour. Increased amounts in the diet are thought to improve performance under stress, promote ovulation, improve infant development, accelerate growth, induce satiety, promote investigative behaviour, lower aggression, encourage self-confidence and act as an anti-depressant.
"Tryptophan is a natural amino acid and it is essential that we ingest some in our diet, but once you go beyond that essential level, tryptophan provides us with many other natural health benefits. It modulates our behaviour and emotions, and in many ways works like Prozac," explains Kerem.
Kerem and his team, which includes scientists from the University of Haifa, and Tel Aviv University, came to their present conclusions after comparing wild chickpeas from Eastern Turkey (cice reticulatum), and comparing their nutritional value to cultivated varieties.
The team began studying chickpeas five years ago because unlike the other founder crops – wheat, lentils, barley, flax and peas, which prehistoric people began farming in the Near East 11,000 years ago, chickpeas are rare and extremely difficult to cultivate.
Wild chickpeas can only be found in several locations in southeast Turkey, unlike the wild progenitors of the other founder crops which can be found throughout Asia.
To grow the chickpea successfully, Neolithic farmers had to transform it from a winter crop into a summer one, to enable them to avoid Ascochyta blight, a serious winter disease caused by fungus, which can wipe out an entire crop.
"This is a major agricultural adventure," says Kerem, a lecturer in the faculty of Agriculture, Food and Environmental Quality Sciences. "It is extremely difficult to modify a plant's growing season, but the Neolithic farmers managed to alter the growing season by several months. Wild chickpeas fruit in early March, domesticated ones give fruit in the summer.
"To make this kind of major agronomical effort when there were so many wild species to choose from there needed to be a reason," continues Kerem. "The other founder crops were picked because of their availability, ease of cultivation, and huge yields. Chickpeas were rare, needed more effort, and had lower yields. What we asked ourselves is what was so unique about the chickpea that these prehistoric farmers were willing to make the effort?"
Kerem and his team believe that prehistoric humans knew instinctively that chickpeas offered something valuable and unique in their diet. "Ancient man was not just looking at the field, he was using his senses," says Kerem. "We believe they could distinguish the higher level of trytophan in the chickpeas and knew that it was good for them."
While it is impossible to replicate the diet that humans ate during this era and test it on modern humans as our diet is too rich, Kerem cites a recent experiment carried out in the US, where pigs were given the choice of eating an ordinary diet, or one rich in tryptophan.
"Pigs are very like humans in many ways, they eat meat and vegetables, and their gastro intestinal system and immune system is like ours," explains Kerem. "Within five minutes of being offered the two meals they switched troughs to eat the food high in tryptophans. They knew instinctively which food was better for them."
"Every animal has a preference for food that is more nutritionally valuable to them," adds Abbo, a plant breeder.
The move to farming was an extremely significant period in human development. It marked the end of a nomadic existence, and the start of a stable and increasingly complex social structure. In this environment, social behaviour and the ability to adapt to change was more important than ever.
"We know that higher tryptophan levels allow better functioning under stress, and changing demographics like the crowding associated with living in communities, is inevitably associated with stress," says Abbo. "In this situation, higher availability of tryptophan becomes an advantage, as it also does in times of human expansion. It is clear that Neolithic humans made a special effort to overcome the difficulties involved in growing chickpeas because they realised that it gave them a unique addition to their diet."
The research appeared in the Journal of Archaeological Science. Kerem points out that this is the first time that scientists have tried to connect changing diet with changing social structures. The team now plans to turn their attention to another founder crop - peas.
Reproduced with permission: Bicom