From "St. Anthony's Fire" to cultivation in saline-alkali land, how did wheat change humanity?

The author of the winning work of the 2023 "China Science Popularization Star Creation Competition": Quasimodo by the River

It was an ordinary day in the 16th century. In Isenheim, a small town in northeastern France, farmers were eating bread made from low-quality wheat and rye as usual. After a while, one person suddenly screamed and then suddenly fell to the ground. Another person felt pain in his limbs, as if he had been burned by fire. Several people had hallucinations and began to become restless and ran screaming. The horrific scene terrified a painter who passed by here. He witnessed these people being sent to a nearby monastery, which specializes in receiving patients with similar symptoms. But the painter found that these people's condition did not improve after entering the monastery, but became more serious. Their muscles began to fester and peel off, and their limbs gradually lost consciousness, then necrotized and fell off, and finally they were greeted with death. A priest shook his head and said to him: "We tried our best, but we really don't know what happened to them. Maybe this is God's punishment for them."

This sudden disease was not uncommon in medieval Europe. For hundreds of years, Europeans could encounter this horrific symptom almost at any time. But what is very strange is that almost all the people who were sick at that time were poor, while the rich rarely got sick. Since the cause of the disease could not be found, the Europeans at that time could only call this disease "St. Anthony's Fire", which means God's punishment for these people. It's just that this time the disease was special, because the painter painted the miserable condition of the patients he saw, and then this group of paintings called "Isenheim Altar" has been preserved to this day, allowing future generations to review what kind of tragedy happened in this small town at that time.

Detail from the Isenheim Altar: The above is actually the pain that humans experience after eating cereals containing ergot.

Image source: Wikimedia Commons

This mystery was finally solved hundreds of years later. It turned out that the culprit of this strange disease was related to the food that the farmers ate at that time. The bread they ate was made from wheat and rye flour, and it was these crops that were contaminated by a fungus called ergot. When wheat grains sprouted, the ergot content in the grains would increase significantly, so these people would become ill.

In 1938, a Swiss chemist extracted a component called ergodiethylamine from the fungus and proved that it was the cause of hallucinations at the time. This substance is also known as LSD, which is a soft drug that can often be heard in the news in today's society. Although this mystery has been solved, there is still a question that has not been answered, that is, why only poor people are prone to diseases, while the rich are much less likely to get sick. To figure out this problem, we need to start with a plant that we can encounter almost every day, that is wheat .

Grains infected with ergot. Image source: Wikimedia Commons

Wheat is one of the most common crops today. More than one-third of the world's population relies on wheat as their staple food. It is also the most widely planted plant in the world. In 2014, the emergence of a best-selling book made the relationship between "humans and wheat" an interesting topic. This is "Sapiens: A Brief History of Humankind" written by Israeli historian Yuval Noah Harari. In this book, Harari uses a very unique perspective to review the history of our ancestors from birth to modern society. In particular, he broke through the boundaries of history before and after the invention of human writing. Before the invention of writing, it was the expertise of biologists and archaeologists; after the invention of writing, it was the expertise of historians, political scientists and economists. Harari happened to have some knowledge of archaeology and history, so this book is both interesting and easy to understand.

In this book, the author puts forward a very interesting point, which is that "humans think they have domesticated plants, but in fact, plants have domesticated Homo sapiens." In order to support his point of view, the author specifically uses wheat as an example. He writes in the book:

"If we look at the agricultural revolution from the perspective of wheat, 10,000 years ago wheat was just one of many weeds that grew in a small region in the Middle East. But within 1,000 years wheat was suddenly all over the world. Survival and reproduction are the most basic evolutionary criteria, and by that standard wheat is the most successful plant in the history of the Earth... The secret of wheat was to manipulate Homo sapiens and use it for its own benefit."

The Gleaners, a famous work by the famous French painter Millet: Wheat provides food for humans, but humans are also bound to the land by wheat

Image source: Wikimedia Commons

This view may sound shocking at first, but it does make sense if you think about it carefully. It seems that wheat is the ultimate winner compared to humans. So is it really wheat that domesticated humans? This requires us to go back to the origin of history and see how wheat appeared in the human vision.

About 2.5 million years ago, an inconspicuous grass plant began to appear on the earth. This is the most primitive wheat. After about 1.5 million years, this plant differentiated into two new species with reproductive isolation, namely one grain wheat (T. monococcum) and Urartu wheat (T. urartu). Although differentiated, the two wheats are still very similar in appearance, and they are both normal diploid organisms, just like us humans. After about 1 million years, Urartu wheat and another plant of the grass family, Aegilops speltoides, a plant of the genus Aegilops, hybridized. If it was an animal hybridization, such a cross-species reproductive product would be like a mule, and it would be impossible to produce offspring. But plants are so magical. This new offspring is not a diploid plant like its father and mother. It did not undergo meiosis, which formed a new tetraploid species, which is two grain wheat.

The domestication process of wheat. Image from the Internet

This is not too strange in the plant world, because polyploidy often occurs in plants. Bananas and strawberries commonly seen on the market today are all products of polyploidy. In this way, a few species of wheat lived on Earth for more than one million years. Some of them began to appear in the Mesopotamian region near the Tigris and Euphrates rivers. This region is also called the "Fertile Crescent". There, wheat plants unexpectedly met another creature, which changed their ordinary fate. This creature is human beings.

According to current archaeological evidence, humans began to settle in the Fertile Crescent more than 10,000 years ago. This is the birthplace of the Eurasian civilization and one of the earliest regions in human history where agriculture appeared. Humans planted barley, peas, lentils, beans and figs here. Of course, humans also set their sights on wheat.

Schematic diagram of the Fertile Crescent: The Fertile Crescent is the first region where agriculture appeared and where wheat and barley were domesticated

Image source: Wikimedia Commons

At this time, wheat has adapted to the environment of the Fertile Crescent. The climate of this area is different from that of most parts of the world, because the climate here is characterized by mild and rainy winters and very hot and long summers. Climatologists call this climate the Mediterranean climate. Such a climate has gradually evolved wheat into a unique living habit: before the arrival of winter, wheat seeds begin to germinate and grow into seedlings, and after winter, they grow rapidly and bloom and bear fruit. In order to survive, wheat, like other grass plants, does not choose to rely on insects for pollination. Its petals gradually shrink and the structure becomes very simple, called lodicules; inside the lodicules are two scale-like structures, called "palea" and "lemma", which is the calyx structure of wheat flowers; between the inner and outer palea are the stamens and pistils of wheat flowers.

Once the lodicules come into contact with water, they will swell rapidly, and then the stamens and pistils will be exposed and pollinated by the wind. Of course, for grasses, such cross-pollination is somewhat redundant, because more often than not, pollination is completed before their lodicules swell, which ensures that the species can survive in such a special environment as much as possible. When the long summer comes, wheat has completed the task of nurturing the next generation, and the original mother will die and will not compete with its offspring for food. At this time, all the nutrients in the wheat are concentrated in the seeds. After these seeds mature, they will scatter around their mothers, quietly waiting for the winter to pass, and then start a new cycle of life.

Schematic diagram of wheat flowers Source: daviddarling.info

It is precisely because of this characteristic that it is possible for humans to use wheat. It is also because of this that humans began to adjust their work cycles according to the growth laws of wheat. This is what Harari said about wheat domesticating humans.

But the word domestication contains two meanings. The first is the contact between two organisms, and one of them changes the original living conditions of the other. From this perspective, whether it is wheat domesticating humans or humans domesticating wheat, it seems reasonable; but another meaning of domestication is that one organism can only survive by relying on another organism. For example, after wolves were domesticated by humans, some members became dogs, and dogs are the product of human domestication. For most dogs, once they lose humans, they will hardly have the ability to survive. Only a small number of them will recover their wildness and become wild dogs. If we look at it from this perspective, if humans lose wheat, there are other crops to use, such as rice, barley or corn, but today's wheat, if it loses humans, has lost most of its ability to survive. If we look at it from this perspective, we can only say that humans domesticated wheat in the end, not wheat domesticated humans.

Combine harvester is harvesting wheat. Image source: Tuchong Creative

This means that wheat has undergone at least three major changes since it encountered humans. It is precisely because of these three major changes that wheat has become completely dependent on humans for survival. This is the essence of domestication: domestication is not only a change in an organism, but also the direction of this change is completely controlled by another organism.

From a human perspective, there are natural reasons for the shift from hunting to agricultural life. Before humans domesticated wheat, they had just experienced a warm period. As the temperature rose, the number of organisms in nature also increased, which led to a peak in human population. Unfortunately, just as humans settled in the Fertile Crescent, the temperature began to turn from warm to cold. This is the "Younger Dryas Period" mentioned in our previous program. Hunting wild animals is no longer enough to satisfy the pressure brought by the population, so the shift of humans to agriculture is also an inevitable process, but in this process, wheat was finally chosen.

So what three changes did wheat go through before it was domesticated by humans? The first change was that wheat seeds became larger and larger, and the carbohydrate content of the seeds, that is, the starch content, became higher and higher. This is a very natural process, because when our ancestors planted wheat, they would naturally choose to pass on the offspring with higher yields and fuller seeds. The increase in grain size is naturally related to genetic changes, but environmental factors are also important, because crops are planted in reclaimed land, and wheat does not have to compete with its weed relatives, and can get enough water and nutrients. The nutrients in wheat are mainly stored in the endosperm part of the seed, which is responsible for improving the nutrition of the embryo like the yolk of an egg. As the wheat grains gradually become larger, the main part that increases is the endosperm, so the nutrition contained in the wheat seeds becomes higher and higher.

Comparison between Teosinte and Corn: All the food crops we see today have gone through the same process as corn, from having few and shriveled seeds to becoming plump and full.

Image credit: Nicolle Rager Fuller, National Science Foundation

Of course, this step alone is not enough to make humans prefer wheat, because any crop will produce similar results after a long period of screening. At this time, wheat underwent a second transformation, which was originally very unfavorable for wheat plants, but was very beneficial to humans. That is, the stems of wheat, or leaf axes, began to become stronger. Why is this unfavorable to wheat? It turns out that under natural conditions, the brittleness of the leaf axis changes along with the maturity of wheat seeds. Once the wheat seeds begin to mature, the leaf axis begins to become brittle, so that it does not take a lot of wind to blow off the leaf axis, and the wheat seeds will be scattered all over the ground. At this time, the wheat has completed the seed propagation; and once the leaf axis becomes firm, the wind can't easily blow away these mature seeds, which is very unfavorable for the spread of wheat seeds. If it is in the wild environment, other weeds can easily occupy the territory that originally belonged to wheat, and wheat will face the risk of extinction. But it is also this characteristic that is very friendly to humans. The wheat planted in this way can be harvested all at once, without picking seeds one by one on the ground, and the production efficiency is greatly improved. As for the wheat of the second year, it was the result of humans sowing again. Humans replaced wheat to complete the last step of reproduction.

As a result, wheat quickly became the main food crop in ancient West Asia and even Eurasia. At the latest in the Shang Dynasty, wheat was introduced to my country from West Asia along with bronze manufacturing technology, and became one of the five grains in ancient my country. By the way, there is controversy about which five crops are the five grains, but no matter which statement is true, wheat, sorghum (also known as millet), millet (also known as millet or millet), and soybeans (also known as beans) are all included. Today, of these four crops, only wheat has become the main food crop, and together with rice and corn, it constitutes the main source of carbohydrates for us humans. As for sorghum and millet, they have completely become supporting roles. So what happened in this process?

There are different opinions on what the five grains are. According to Mencius, they are "rice, millet, millet, wheat, and beans".

Image source: Tuchong Creative

This brings us to the third transformation of wheat. As we mentioned earlier, before humans encountered wheat, there were already diploid Einkorn and Urartu wheat, as well as tetraploid Emmer wheat that had undergone a genetic mutation. After wheat encountered humans, its genes continued to change. About 8,000 years ago, Emmer wheat accidentally hybridized with a distant relative of its own, the wild goat grass plant Aegilops tauschii (also known as rough goat grass), forming common wheat, which is the most commonly consumed wheat variety today. Common wheat once again underwent a genetic change, changing from a tetraploid plant to a hexaploid plant.

The product of this hybridization is not only the expansion of the genome, but also the change in the shape of wheat. The ears of previous wheat varieties were flat, which we can understand as a two-dimensional structure, while the ears of ordinary wheat became square, that is, a three-dimensional structure. This change has at least doubled the yield of wheat and made the wheat seeds more swollen. It is this change that has gradually made wheat stand out among the five grains and become the most important food crop in northern my country.

It is precisely because of these three changes that wheat has become a creature that can only survive on humans, just like cows or domestic dogs. Humans domesticated wheat and quickly brought it to the world.

Of course, for crops like wheat that are enough to change the course of human development, domestication is no longer just a connection between these two organisms. While domesticating wheat, many other organisms have also been affected. With the cultivation of wheat, various other "wheat" species have also entered the human table because of wheat. The first is barley, which was also domesticated by humans more than 10,000 years ago and is also a product of the Younger Dryas event. However, compared with wheat, the yield of barley is much lower, so its influence is much smaller than that of wheat. The Qinghai-Tibet Plateau in my country is an important production area of ​​barley. Barley still has an important influence on the Qinghai-Tibet Plateau, but in this area barley has been renamed and is called Qingke. In the process of planting wheat, wheat's distant relatives and neighbors always come uninvited, and they will compete with wheat for nutrients, which is naturally not liked by farmers at the time.

The barley in the Tibetan valley is ripe. Barley is a subspecies of barley. Image source: Tuchong Creative

However, over a long period of time, some varieties of wheat were domesticated by humans, including oats and rye. They replaced the role of wheat in an environment that was not conducive to wheat growth: oats mature earlier than wheat, and oats can survive in a more humid environment, while rye is much more cold-resistant than wheat, so they all became substitutes for wheat. However, compared with wheat, they either taste bad or have a lower nutritional content than wheat, so they still cannot shake the position of wheat on a global scale. In particular, they have another problem, which is the ergot disease mentioned at the beginning of our article. Rye and oats are more susceptible to ergot infection than wheat, which also answers why the poor are more susceptible to the "St. Anthony's Fire", because high-quality wheat flour was a luxury on the table in the Middle Ages, and only the rich could enjoy it every day, so the risk of infection with ergot was much lower, and the poor were more likely to be satiated by rye, oats and inferior wheat, so they were more susceptible to the disease.

As for another plant called "wheat", it is buckwheat. It is also a weed that grows with wheat and was discovered by humans. However, although it is called wheat, it has nothing to do with the wheat plants mentioned above. Because it is a dicotyledonous Polygonaceae plant, it is not a grass plant at all. It is just that it is more tolerant to poor soil than wheat, so it has become a substitute in areas where wheat cannot be grown.

Buckwheat plants, whose beautiful flowers can distinguish them from other "wheat" Source: Wikimedia Commons

Today, we can basically figure out the origin of crops and their relationship with each other, and one scientist played a great role. He is the Soviet scientist Nikolai Ivanovich Vavilov. Vavilov devoted his life to crops. Under his research, humans basically figured out the origin of wheat, barley and corn. Later, he also served as the president of the All-Soviet Academy of Agricultural Sciences and undertook an important task: to collect seeds from all over the world as much as possible and store them in the world's largest plant seed bank. During World War II, Leningrad, where the seed bank was located, was surrounded by the German army. During the 28-month siege, plague and famine were rampant in the city. Hunger also threatened the scientists who guarded the seed bank. But despite this, these scientists never thought about eating seeds. One of Vavilov's assistants starved to death during the siege and fell in front of the seed bank he was guarding.

It can be said that it was almost by Vavilov's own efforts that the Soviet Union's agricultural technology reached the world's leading level. However, as agriculture began to take a detour after the Soviet Union, Vavilov failed to realize his lofty ambitions. In the end, a group represented by Lysenko occupied the mainstream position of Soviet academia. They completely denied genetic genetics based on facts. Eventually, the Soviet Union's scientific cause stagnated completely, especially the agricultural level regressed very seriously, and his bad influence has not completely dissipated to this day. This incident also gave scientists around the world a heavy warning: in the face of truth, scientists need to make a lot of efforts, and even their lives.

In 1968, when Vavilov finally regained his honor, the seed bank he once guarded was named after him. This is the Vavilov Institute of Plant Production. To this day, this seed bank is also one of the largest plant genetic databases in the world. In 1977, the asteroid No. 2862 discovered by Soviet astronomer Nikolai Chernykh was also named after Vavilov. On the back of the moon, there is also a Vavilov crater, which was named in memory of him and his physicist brother. It is because of the unremitting efforts of this scientist that we can understand the story of wheat and find a direction for the transformation of wheat in the future. Due to the special structure of common wheat hexaploid, it is much more difficult to hybridize wheat to cultivate more advanced varieties than hybrid rice. So far, hybrid wheat technology has not been commercialized.

Vavilov Source: medium.com

However, scientists have not reached a dead end. With the advancement of genetic biology, we can use more advanced technology to improve wheat varieties and further domesticate wheat. One of the directions is that the scientific community is trying to make wheat more salt-tolerant, so that wheat can be grown even in saline-alkali land. At present, this technology has been successful in the laboratory and has begun field trials in saline-alkali land in my country. As of 2022, my country has achieved the feat of planting wheat on 2.4 million mu of saline-alkali land. These saline-alkali lands, which were regarded as "wasteland" and "harmful land", have become fertile land for grain production under the efforts of scientists. Not only can wheat be harvested, but the land can also be gradually managed. And this method is just a microcosm of the Chinese use of wheat. New wheat breeding technologies such as "two-line hybrid wheat", "three-line hybrid wheat" and "DH technology" have given wheat more potential and made the national strategy of "storing grain in technology" possible.

Major events in China's saline-alkali land wheat technology Source: People's Daily Online

It seems that the bond between humans and wheat will not end. Instead, as human wisdom progresses, wheat will continue to shape human civilization.

References:

[1]Bryda, Gregory (June 2018). "The Exuding Wood of the Cross at Isenheim." The Art Bulletin 100.2: 6–36.

[2]Poinar Jr., G.; Alderman, S.; Wunderlich, J. (2015). "One hundred million year old ergot: psychotropic compounds in the Cretaceous?"

[3]Agrios, GN 2005. Plant Pathology. 5th ed. Elsevier–Academic Press, Boston.

[4] Yuval Noah Harari (Israel). A Brief History of Humankind. Beijing: CITIC Press

[5]Hancock, James F. (2004) Plant Evolution and the Origin of Crop Species. CABI Publishing.

[6]Huang S, Sirikhachornkit A, Su X et al (2002) Genes encoding plastid acetyl-CoA carboxylase and 3-phosphoglycerate kinase of the Triticum/Aegilops complex and the evolutionary history of polyploidy wheat. Proceedings of the National Academy of Sciences 99:8133–8138.

[7] Wang Yuefu, Du Jinzhe, Liang Zuozheng. Comparative study on carbon assimilation, transportation and distribution of different wheat varieties[J]. Journal of Laiyang Agricultural College, 2006(02):30-34.

[8] Jin Guiyun (2007) Archaeological discovery and research of early wheat in China. Agricultural Archaeology (4): 11–20.

[9] Huang Lianzhen. Talking about Cereals and Grains[J]. Chinese Food and Nutrition, 2004(6):47-49.

[10]Faris JD. Wheat Domestication: Key to Agricultural Revolutions Past and Future[M]// Genomics of Plant Genetic Resources. Springer Netherlands, 2014.

[11] Alice Roberts, Domestication; translated by Li Wentao. Readers’ Publishing House, January 2019.

[12] Wang Yonggang. Exploring the origin and domestication of cultivated barley using gene resequencing and protein content[D]. Huazhong Agricultural University, 2019.

[13] Bandyopadhyay, R., Frederickson, DE, McLaren, NW, Odvody, GN, and Ryley, ML 1998. Ergot: A new disease threat to sorghum in the Americas and Australia. Plant Dis. 82:356-367.

[14] Guan Chengxue, Zhao Jiming (eds.); Zhao Lixing (ed.). Painful Lessons in the History of Science: The Story of Vavilov. Changchun: Jilin Science and Technology Press, October 2012.

[15] Munns R, James RA, Xu B, Athman A, Conn SJ, Jordans C, Byrt CS, Hare RA, Tyerman SD, Tester M, Plett D, Gilliham M. Wheat grain yield on saline soils is improved by an ancestral Na(+) transporter gene. Nat Biotechnol. 2012 Mar 11. doi: 10.1038/nbt.2120.