The Rats, the Flea and the Weather

Although the human flea can transmit Y. pestis, this flea is not the normal vector of this disease in humans. The most common vector is a flea that infests rats and this flea normally prefers rats to any other host. This means that the flea does not usually feed on a human host. So the environmental conditions that can lead to an epidemic of the bubonic plague in humans must also include some reason that forces the rat flea to bite humans. That condition is an increased death rate death in the population of rats. The flea only moves to a non-rat host when the population of rats decreases drastically.

One thing that can kill large numbers of rats is the bubonic plague itself. Rats can tolerate a modest population of the pathogen in their blood stream, but if it invades the lungs or the brain of the rat, this disease becomes lethal to rats (it also kills many domestic animals). Thus an epidemic of the bubonic plague among the rat population of a city can lead to epidemic among the human population of the city and their domestic animals.

Other circumstances can also cause massive die off of rats. For example, in 1994 an outbreak of the plague in Surat India was preceded by massive flooding. The floods drowned many of the city’s rats.

In addition, the climate can influence the severity of the disease. The likelihood of a flea’s bite transmitting the pathogen increases when the temperature is between 20 and 25 degrees C. At this temperature the bacilli multiply in the flea’s stomach in numbers large enough to cause a blockage and threaten the flea with starvation. This causes the flea to try to clear the blockage by regurgitation. If the temperature rises above 27 degrees C, the blockage in the flea’s gut dissolves. Also the larvae of the flea will die if the humidity is too low. Thus a cool, moist climate is the optimum for both the survival of the flea and transmission of the disease. And this was exacerbated by the Fusarium toxins in the food the people of Europe were eating during the Middle Ages.

Today, in the age of vaccines and informed physicians, we lack experience with epidemic diseases and both the general public and modern historians tend to underestimate the full force a new infection can have on a population. Thus we all overlook the role diseases have played in the course of history. We are even less aware of how plant diseases can influence the affairs of humans. Yet both have and will continue to significantly influence human health. And both are influenced by the weather, which, as I am trying to get across, is influenced by the global climate of the time!

“Biology and medicine prove to be crucial driving forces in human history…” Jared Diamond

Next Post: Other Casualties of the Black Death

And There is Even More to it Than That!

If the change in global temperature brings more rain to an area than it is used to, as happened in Western Europe during the Middle Ages, then it also means plant disease can increase and that in turn can increase the devastation caused by human disease. For example, during the Late Middle Ages, a postharvest disease caused by a fungus called Fusarium is believed to have increased the deaths caused by the bubonic plague in areas with increased rain.

Generally this fungus contaminates the seeds either before they are harvested or at the time of harvest. This fungus then grows within the seed during storage. For this fungus to continue to grow it requires a high moisture content in the seeds. Today most grain is stored at a moisture content of 12-14% which is too low for the fungi to grow and the fungi die after a few months in storage and do not infect other seeds. However during the Late Middle Ages, the people had neither the technology nor the knowledge to store grain at this moisture content. During the 13 and 1400’s the moisture content of harvested grain was at the mercy of the weather. Because the weather was moist during this time the moisture content in the seeds must have been high. The fungi in contaminated seed would have continued to grow under these conditions and would have infected other seeds.

As the fungus grows within a seed it not only causes decay of the seed but it also produces substances called mycotoxins. The ingestion of moldy grain containing these toxins can lead to a disease whose symptoms include necrosis of the skin, hemorrhage, liver and kidney damage, and death. Fusarium molds produce a number of mycotoxins. These toxins in both lethal and sublethal doses not only cause the above symptoms but they can also cause an immune deficiency. The toxins attack the lymphoid cells critical for the body’s defense against infection.

According to Mary Kilbourne Matossian in her book Poisons of the Past, the highest moralities of the plague during the late Middle Ages occurred in areas where surplus grain was stored (thus there would also be a surplus of rats) and with the incidence of high humidity, rain, and flooding.

“For two years prior to the pandemic of 1348 in Europe the weather was extraordinary rainy and humid and crops were poor. The summer of 1348 was exceptionally wet in England, where the plague began its ravage; on the other hand it was not so wet in Scotland that year and the plague did not spread widely there until the wet summer of 1350.

The coldest and driest regions were untouched by plaque during the pandemic. Iceland, northern Norway and Sweden, Finland and large areas of Russia and the Balkans escaped the blight. So did the mountainous and desert areas of the Near East.”

Mary K. Matossian

Knowing that toxin producing fungi like Fusarium flourish in moist conditions, Matossian speculates that the ingestion of moldy grain by the rats markedly increased the mortality of rats thus increasing the likelihood that the rat flea would move to other animals including humans. (The mortality of horses, cattle, sheep and goats was exceptionally high during the wet period between 1345 and 1350). In addition, the humans were eating bread made with the moldy toxin-infested grain. The ingestion of mycotoxins would have compromised their immune system making them more likely to die when exposed to the plague pathogen. Thus, the increased mortality rates in some places most likely can be explained by a combination of the virulence of Yersinia pesti, the bacteria that causes disease known as the Black Death, and immune deficiencies caused by mycotoxin food-poisoning in both rats and humans

“Man does not live by bread alone - but he must have bread. And he must have bread that is truly the staff of life, not a scepter of death.”

Mary K. Matossian

Next Post: The Rats, the Flea and the Weather

After the Fall of Rome

The first civilizations (Sumeria, Eygpt, Myceanea etc.) were more or less isolated from each other. With the second rise of civilization in Europe and Asia (i.e. the Roman Empire and the Han Dynasty in China) things get a bit more complicated. This was because the world’s population centers were no longer isolated from each other. That meant something new – the movement of human diseases.

Routine travel by sailing ships and by caravan across the length and breadth of the Old World began to reach its peak organization between 100 and 200 CE. During this time thousands of people began to travel the trade routes established between the four centers of civilization, from China through India and the Middle East to the Mediterranean and back. And with them came disease, human disease.

According to William McNeil in his book Plagues and Peoples, between 150 and 600 AD, “new” infectious diseases attacked the people of both China and Rome. These diseases killed millions of people and the social impact of this heavy death toll was devastating. One of those diseases was Bubonic Plague. This disease is believed to have been a part of the demise of the Roman Empire but in the 1300’s it hit Europe with a vengeance.

Let’s take another look at the climate over the last 6000 years (graph above). Look at the temperatures after Rome declines. There is a small dip in the global temperature. That was enough to bring down Rome and plunge the European world into a second Dark Age, or the Early Middle Ages.

The temperature rises again to where it was before Rome declined. This is time period historians call the High Middle Ages. It is also called the Medieval Warm Period. This was a good time in Europe. During this period populations increased in Europe and wheat grew well all the way north into Scandinavia.

Then the global temperature falls again during a time called the Late Middle Ages. This is the beginning of what scientists call The Little Ice Age.

“Around 1300, centuries of European prosperity and growth came to a halt. A series of famines and plagues, such as the Great Famine of 1315–1317 and the Black Death, reduced the population by as much as half according to some estimates. Along with depopulation came social unrest and endemic warfare.”

The Little Ice Age Temperature Graph

The temperature rises slightly again (see graph above) and we have the Renaissance, another good time in Western Europe and then Europe gets hit again with cold temperatures, the coldest period of the time called the Little Ice Age.

In his book, "The Little Ice Age: How Climate Made History, 1300–1850", anthropology professor Brian Fagan of the University of California at Santa Barbara, tells of the plight of European peasants during the 1300 to 1850 chill: famines, hypothermia, bread riots, and the rise of despotic leaders brutalizing an increasingly dispirited peasantry. "In the late 17th century," writes Fagan, "agriculture had dropped off so dramatically that Alpine villagers lived on bread made from ground nutshells mixed with barley and oat flour. Finland lost perhaps a third of its population to starvation and disease.”

Can you see a pattern here? When the weather is good for farming, populations grow and prosper. When weather for is bad for farming, populations decrease because of starvation, disease, and warfare.

Next Post: And There is Even More to it Than That!

What Causes the Jet Stream to Change its Course?

Usually changes in “normal” weather patterns reflected in the movement of the jet stream are short lived. However, sometimes the jet stream moves north or south for more extended periods of time. So what can make the path of the jet streams change?

Remember that it is the sun's heating of the earth, of its land, and its water that drives the weather. To change the weather then, it is necessary to change the absorption and distribution of the sun's energy.

There are two basic ways to do this:

1) Change the amount of solar radiation that reaches the earth or

2) Change the amount of sun's energy that radiates back into space.

Clouds, for example, block the sun’s rays from reaching the ground by reflecting the sunlight back into space. We all have experienced the cooling effects of clouds on a warm summer day. Clouds also prevent the heat radiating back from the earth from reaching outer space. As any farmer knows, cloud cover can prevent a very cold winters night from reaching freezing temperatures. Because cloud cover has both a cooling and a warming effect the net effect on the overall climate is nil.

Dust in the upper atmosphere also reflects sunlight back into space but unlike clouds its net effect is anything but nil. Dust tends to cool the high latitudes more that those at the equator. Remember that the path of the sunlight that reaches the poles is longer than that at the equator. If the atmosphere is dusty, the sunlight has a longer path through the dust and more of the sunlight is reflected back. This of course increases the temperature differentials at the boundary between Arctic and equatorial air and therefore increases the force of the winds and the strength of the storms. One of the most important sources of atmospheric dust is violent volcanic explosions. These explosions can throw tremendous amounts of debris high into the atmosphere which then circulate around the globe for years and are believed to affect the climate all over the globe.

The correlation of volcanic eruptions and climate has been made relatively recently although the consequences of such eruptions have been recorded, albeit unwittingly, throughout history. For example, Roman poets tell us of the eruption of Mt. Etna in Sicily in 42 BC and at the same time an historian in China writes of a "veiled and indistinct" sun and crop failures. More recently, Benjamin Franklin wrote in May 1784 of a constant fog over all Europe during the summer months of 1783 and the most severe winter in Europe for many years. He knew about volcanic eruptions in Iceland about that time and speculated that there might be a connection but he did not know of the eruption in Japan in the 1783. There were crop failures and poor harvests in France during this time that are believed to have contributed to the social unrest preceding the French Revolution in 1789. In June 1991 the dust from the eruption of Mt. Pinatubo in the Philippines more than doubled the normal amount of dust in the air. The dust cooled the climate, brought spectacular sunsets to Hawaii, caused ash induced damage to jet plane engines, and some believe, disturbed weather patterns in southern Africa. In 1992 and 1993 Mozambique, Zimbabwe, and South Africa suffered a drought which withered crops and caused a food shortage throughout the region.

In his book Catastrophe, D. Keys believes there is strong evidence that in 535 AD there was a major volcanic eruption that devastated the climate all over the world. Its location was mostly likely in Indonesia between the islands of Sumatra and Java where the notorious volcano of Krakatoa is located. The climate disruption from this massive eruption lasted for 20-30 years and affected every know civilization of the time. If this is true, and it probably is, this was the final blow to the Roman Empire.

For many places in the world, recovery did not come until 800 AD or later. But this recovery was short lived as the global temperature fell again with devastating effects throughout the world.

Ice cap studies together with historical records and tree ring growth data showed that there was a long time of increased volcanic activity from 1250-1500. This was exactly at the time of the Bubonic Plaque in Europe, the end of the Mississippi culture (the Mound Builders) in North America, and demise of the Viking colonies in Greenland and Iceland. It was the beginning of another period of global cooling that became what scientists call the Little Ice Age.

Next Post: After the Fall of Rome

Different Weather for Different Places

Let’s summarize what we know about the connection between the world’s climate and the rise and fall of human civilizations so far.

When the Last Ice Age of the Pleistocene ended around 10,000 BC, the world’s average temperature rose slowly, then between 6000 and 3000 BC average temperature increased at a slightly faster rate. By 3000 BC, global temperature was about 2 degrees C above the temperature of 6000 BC. Then from 3000 BC to around 1000 BC, the global climate began to cool. By 1000 BC, the global average temperature was about the same as it had been in 6000 BC. After 1000 BC, the average global temperature began to become warmer again.

It appears that the warming climate after the last ice age and an increasing human population precipitated a change from food gathering to food production in many regions of the world. By 3000 BC, people all over the world had domesticated plants and many began to settle in permanent farming villages. The cooling temperatures after 3000 BC, however, had different effects depending on where these farmers were located.

The cooling weather weakened the jet stream and in some places that meant the rainfall became more inconsistent. In the Near East, state governments formed to conserve water and grow more food to feed their growing population. During this time, the changing climate had little effect on the social organization in China. Society remained one of small villages and chiefdoms. By 2200 BC however, the wanderings of the weakened jet stream brought increased droughts, fewer monsoons, and the “east wind” to the Near East. It also brought increasing rains to Northern China.

Around 2200 BC a state society evolved in China to control the flooding caused by the increased rain. As we learned earlier, while agriculture failed in the Near East, it grew in China. As the influence of the Zhou increased southward, rice became important to the Chinese economy along with millet and their carrying capacity rose. In the Americas, the changing weather must have allowed for the growing of surplus food and farming villages of the Olmec and the Chavín grew into state societies. While in the Mediterranean, civilizations fell apart during the time period between 1200 and 700 BCE.

Then around 750 BCE, the global temperature began to rise again. As the global climate warmed, the path of the jet stream and its patterns of rainfall would have changed again. During this same time period China, the Chavín and the Olmec fell into crisis and by 200 BC the civilizations of the Chavín and the Olmec were a memory. Between 700 and 200 BC the state government of China could no longer maintain control and the country became segmented and ruled by warlords.

Civilization along the Mediterranean however, began to recover. Around 200 BC Rome emerged as the “greatest power the West had ever known” but by 450AD, the glory of Rome was over. Between 200 and 600 AD the global climate was cooling. This means that the paths of the Jet Stream were unstable yet again.

Next Post: What Causes the Jet Steam to Change Its Course?

Rust Again

In 700 BCE, when Rome was only a few farming villages along the Tiber River, the Roman farmers knew well of this rusting sickness that made their wheat useless for food or for seed. To stop this plague the priests of primitive Rome began to placate a new god. His name was Robigus, the god of rust. The ceremony that evolved to calm the anger of Robigus was held during the Spring Festival in the third week in April and included the sacrificing of a red dog, the pouring of red wine, and the following prayers:

Spare our crops, O Robigus.
Is it not enough that thou couldst harm them?
Accept, O mighty god our sacrifice.
Take it, O Robigus, and not our wheat!
Drink the red wine O god!
As we stand humble before thee

Spare us from the baleful glare of Sirius the dog star.
Still the blasting winds from the eastern sky.
Grant us our crops, the labors of our hands,
And we in holy gratitude
Will honor thee forever more.

Quoted from Famine in the Wind by G. L. Carefoot and E. R.Sprott

Did you catch it??? Still the blasting winds from the eastern sky.

In addition it must be remembered that the territory of the Roman Empire by 117 CE included all the land surrounding the Mediterranean Sea, north and south, including Egypt (see map below). And by 200 CE most of Rome’s food was being shipped from North Africa.

The soil of Africa has been given over by nature entirely to Ceres [goddess of agriculture and especially grains]; the oil and the vine have almost been refused; all the glory of the country is in its [wheat] harvest.

Pliny the Elder, a Roman scholar.

During the time of the Roman Empire, as in the time of the New Kingdom in Egypt, grain harvests in the Mediterranean were vulnerable to the whims of the region’s temperamental weather. These whims include winter floods that inundated newly-sown fields, scorching dust-laden winds that blew from the South (siroccos) that could cause the wheat kernels to shrivel before attaining maturity, clear skies too early in the spring that portended severe frost damage, and the east wind. As before, the east wind meant moisture. An east wind during the growing season meant wheat plants soaked with water, which enabled the spores of the wheat rust fungus to germinate and infect their hosts. Although many farmers knew there was some connection between wet weather and bad rust years, there was not much they could do about it except pray to Robigus.

Historical records and studies of growth rings of the old trees on both the African and European shores of the Mediterranean indicate that from 100-300 CE the climate was unusually wet. We can only conclude that the crops of the Roman Empire must have been ravaged by rust during the later part of the Empire. The three components for an epidemic were present, the plant (wheat), the pathogen (the rust fungus), and wet weather. The destruction of the food supply caused by rust probably contributed to the “Crisis of the Third Century”.

Like all other civilizations before and after, the economy of the Roman Empire, the defense of the Roman Empire, and therefore the survival of the Roman Empire were tied to agriculture. And if you are dependent on agriculture you are dependent on the weather - too dry and you lose your food source to drought - too wet and you lose it to flooding or disease.

Next Post: Different Weather for Different Places

Rome and More

In the Mediterranean, the time period between 1200 and 700 BCE is known as the Greek Dark Ages. Basically civilization there fell apart. Then around 750 BCE, civilization along the Mediterranean began to recover. Notice on the climate graph that the global temperature was rising.

First Mesopotamia evolved into the Persian Empire (612-330 BCE), then Greece recovered (750-146 BCE) and final the Roman Empire took over the entire Mediterranean (264 BCE-235 AD). By 450AD however, the glory of Rome was over. What happened?

Today, most historians would concede that no single factor can be blamed for the decline of this great civilization. As with all “extinctions” many things contributed to its fall. But perhaps one of the most interesting things about this period is that Rome was not the only empire to decline during this time.

Rome was not alone in its plight. In the years between 200 and 600 AD, empires were under siege all across the broad civilized belt that stretched from Rome in the west to China in the east.

Empires Besieged by the Editors of Time-Life Books

The world has grown old and lost its former vigor ... the mountains are gutted and give less marble, the mines are exhausted and give less silver and gold ... the fields lack farmers, the sea sailors, the encampments soldiers ... there is no longer any justice in judgments, competence in trades, discipline in daily life ... the Day of Judgment is at hand.

Cyprian, Bishop of Carthage, c. 250 AD

In China, the Han Dynasty, which had taken control of China sometime after the Warring States period and who had ruled successfully for nearly 400 years, fell apart and Chinese society was again plunged into a series of vicious civil wars. The political instability and conflict lasted from 189-589 AD. Nomads from the north (the Mongols and the Huns) took advantage of this turmoil, moved in, and took over.

By 500 AD the Gupta Empire in India (which included Indus) and New Persian Empire (which included Mesopotamia) were also toppled by the pressure of barbarian invasions. Like the time between 1200-1000 BC, there seemed to be a “general crisis of the civilized world”. This time the crisis also included China and again the “uncivilized” people from the Eurasian Steppes and the deserts of Arabia and North Africa were on the move. The previous crisis of 1200 BC was correlated with a changing global climate. Was there a climate change this time as well?

If you look back at our climate graph, you will see that indeed there was a climate change from 200-600 AD. For the first 200 years of Imperial Rome the climate was stable, then around 200 AD, the temperature began to drop. You will notice that the magnitude of the drop is not nearly as dramatic as that when the Near East Civilizations declined. Yet the average global temperature around 400 AD is about the same as it was around 2200 BC, the beginning of the 300 year drought in Mesopotamia. This probably means that the northern jet stream had moved enough to cause the same general effects that it had before.

The first people that would have felt the effects of these climate changes would have been the “uncivilized” nomads of the North and the South, Rome’s, India’s, Persia’s, and China’s “barbarians”. These people lived in very fragile ecosystems with minimal carrying capacity. In addition, there were a lot more people in both the civilized and uncivilized worlds in 200 AD than there were in 2000 BC. In 2000 BC the world population was only about 25 million people. In 200 AD there were over 200 million people. In both the civilized and uncivilized worlds, the populations were at or were approaching the carrying capacity of their respective environments. Even a relatively small decrease in the global climate would have lowered that carrying capacity enough to send the nomads in search of greener pastures, literally. The nomads that took over China, for example, turned farmland into pastures for their livestock. For the “civilized” farmers, the decreasing temperature would have meant decreasing yields and for the farmers of the Roman Empire, it must have meant rust epidemics.

Next Post: Rust Again

Wheat Rust

Of all the diseases of wheat, and there are many, rust is by far the worst. All plant rusts are caused by the infection of a plant by a Basidiomycete fungus. Most Basidiomycetes are fleshy fungi that produce mushrooms, conks, and puffballs and are either saprophytes or wood decaying organisms. But the Basisiomycetes also included two destructive groups of plant pathogenic fungi, the rusts being one of them. Wheat plants are susceptible to three different rusts, stem rust (Puccinia graminis), leaf rust (Puccinia recondita), and stripe rust (Puccinia striiformis). Of these, the most serious one is stem rust. Stem rust affects wheat where ever it is grown, decreasing yields and in bad years even killing the plants. Bad rust years in North America, for example, can cause losses of tens to hundreds of million metric tons of wheat.

The stem rust fungus attacks the stem, the leaves, and the tissue around the seed heads of the wheat plant. It causes blisters that eventually rupture the epidermis, exposing a powdery mass of rusty red-colored spores, hence the name. These spores, called uredospores, can reinfect the same wheat plant or infect other wheat plants. The uredospores are easily picked up by wind currents and blown hundreds of miles away from their original source. If a uredospore lands on wheat plant, it will germinate in the presence of moisture and send a hyphal strand, called a germ tube, into a stomata. The fungal hyphae ramify through the plant tissue, penetrating mesophyll cells and draining them of their soluble foods. Within 8-10 days after infection, the fungus makes spore-producing structures that rupture the epidermis and produce more uredospores.

The importance of the East Wind to the rust fungi in Ancient Egypt was two-fold. First the winds pick up the fungal spores from infected plants and deposit them in the wheat fields of Egypt. Second the winds are followed by heavy rain clouds that sweep over the coast into the Eastern Mediterranean providing rain and thus the moisture for spore germination. Wheat rust is always much worse in moist or wet weather because more spores germinate and infect the wheat plants. The pharaoh did not stand a chance. With little understanding of the causes of disease, there was nothing he could do to preserve maat in the face of “blasting” East Wind.

Next Post: Rome and More...

A Bible Story

During the time Egypt was ruled by the Hyksos, Jacob and his twelve sons were living in the Levant, in Palestine. As the story goes Jacob loved one son, Joseph, “best of all his sons” and Jacob gave Joseph a special long tunic. His brothers were jealous of Joseph and his new tunic so one day, when they were tending their flocks, they striped Joseph of his tunic and sold Joseph as a slave to a passing caravan of traders on their way to Egypt. The bothers then tore the tunic, stained it with blood, and told their father a wild beast had devoured Joseph. Joseph’s father “mourned his son for many days”.

When the traders reached Egypt, Joseph was sold again to the Pharaoh’s chief steward. Joseph served his master well and soon was put in charge of his master’s affairs. Then one day he was falsely accused of molesting this master’s wife and thrown in to jail. In time, the chief jailer put Joseph in charge of all the prisoners including two prisoners that had been in the service of the Pharaoh. One night while in prison, the Pharaoh’s servants each had a dream. The next morning Joseph interpreted their dreams. He told them that in three days one of them would be hanged and the other would be released to again serve the Pharaoh. As it turned out, the third day was the Pharaoh’s birthday and the dreams came true. One was reinstated and the other was impaled.

Two years later the Pharaoh had two disturbing dreams. The next morning he summoned his “magicians and sages” to interpret his dreams but they could not. Then the servant that had been in jail remembered Joseph and told the Pharaoh about him. The Pharaoh summoned Joseph from the dungeon and asked him to interpret the dreams, telling him:

In my dream, I was standing on the bank of the Nile, when up from the Nile came seven cows, fat and well-formed; they grazed in the reed grass. Behind them came seven other cows, scrawny, most ill-formed and gaunt. Never have I seen such ugly specimens as these in all the land of Egypt! The gaunt, ugly cows ate up the first seven cows. But when they had consumed them, no one could tell that they had done so, because they looked as ugly as before. Then I woke up.

In another dream, I saw seven ears of grain, fat and healthy, growing on a single stalk. Behind them sprouted seven ears of grain, shriveled and thin and blasted by the east wind; and the seven thin ears swallowed up the seven healthy ears.

Genesis 41 17-24

Joseph told the Pharaoh that the dreams meant that there would be seven years of great agricultural abundance in Egypt followed by seven years of famine. He recommended that the Pharaoh appoint someone to collect and store grain during the seven good years to protect against the famine in the seven bad years. The Pharaoh was so impressed, he put Joseph “in charge of the whole land of Egypt” to do just that.

Now the importance of this story is not its happy ending for Joseph, but the words “grain...blasted by the east wind.” or in the German translation of the Hebrew word “yeraqon”, “yellowed by the east wind”. According to the authors of Famine on the Wind (G.L Carefoot and E.R Spout, 1967), the east wind refers to a weather pattern that brings cyclonic storms over the Mediterranean that bring rain and moisture to the East Coast of the Mediterranean during the winter and early spring months. This is during the time of Late Emergence and Early Drought, when the grain of Egypt would be growing and most susceptible to disease. And the disease that probably blasted or yellowed the grain was wheat rust.

Next Post: Wheat Rust?

What Happened?

The story of the rise and fall of Egyptian civilization is one of many ups and downs. Egyptian scholars have suggested “that the ups and downs of Egyptian civilization can be traced to successful or unsuccessful adaptations to fluctuating ecological conditions along the Nile and the management of agricultural and labor surpluses in face of those conditions” (from First Cities by A. P. Andrews). Clearly one of those ecological conditions was one the Egyptians had little control over despite their faith in their religious rituals, the weather.

Egyptian life revolved around the rise and fall of the Nile’s waters and the growing and harvesting of crops. The Egyptian year began in the middle of July when the water from summer rains in the African tropics flowed over and inundated the flood plains of the Nile. This time of the year was called the time of Innundation. The next season, from September to January, was the time of Emergence as the land reappeared from under the flood water and it was tilled and planted. The third season was the Drought. It started in February and was the time the crops were harvested and the state collected surplus grain (taxes). This surplus fed the pharaoh, his household, the households of all the government officials, and anyone else in favor with the king. It also fed the army and the monument builders. When the annual flood did not come, neither did the surpluses.

Generally the cyclical pattern of the Egyptian seasons was dependable and predictable, a phenomenon the ancient Egyptians believed was due to the activity of their gods. The Egyptians called this godly power maat , a term that roughly encompasses our concepts of justice, truth, and order (cosmic and social). When the power of maat failed, as it did at several times in early Egyptian history, social order broke down and the prestige of the pharaoh, who was charged with the administration of maat, was undermined. But the fault was not always due to the pharaoh’s incompetence. It has been suggested that one of the reasons for maat ‘s failure might have been the phenomenon we know today as El Niño. Scientists believe that there have been major El Niño events for at least the last 5000 years and recent El Niño’s have been linked to a decrease in the flow of the Nile. When an El Niño event ends there are usually very heavy rains and floods. More likely, however, the drop in global temperature which started around 3000 BC was to blame.

Soon after 3000 BC actual records of the time show that the level of annual floods of the Nile dropped, and after 2200 they came at roughly 200-year interval. There were some sequences of years when the level was so low as to cause starvation in Upper Egypt. The worst of all these times may have been 1200 BC, when it is suspected that widespread aridity provoked migrations of peoples throughout the Near East.
H. H. Lamb

But there may be more to it than that….

Next Post: A Bible Story

Egypt: The History

Historians divide the history of Egypt into four periods: the Pre- and Early Dynastic period (3150-2700 BC), the Old Kingdom (2770-2200 BC), the Middle Kingdom (2050-1786 BC), and the New Kingdom (1560-1087 BC). Notice the dates. Egypt was in flux from 2200-1087. Then go back to our climate graph…. This is the same time that Sumer and Mycenae faltered – when the climate was getting cooler.

Good weather for farming: the Pre- and Early Dynastic period (3150-2700 BC)

During the first period, Egyptian society moved from an egalitarian society to chiefdoms and then to a state. By the end of the Pre-dynastic period several regional chiefs from the larger towns had gained administrative control over other settlements and the surrounding countryside. Their power came from their ability to manage food production and distribute food in times of shortages. Grave goods found in burial sites excavated from this era indicate there as an increasing social stratification and the emergence of an elite.

Sometime around 3050 BC, Upper and Lower Egypt were united under a single leader and the Egyptian State was born. Cities grew larger and the power of the ruling “chief“, now called a pharaoh, grew stronger. An elaborate religious institution formed, a standing army was created, and an administrative bureaucracy of scribes, tax collectors, census takers, and irrigation managers emerged. Controlling this bureaucracy was the grand vizer, second only to the pharaoh. Along with the bureaucracy came the development of the Egyptian’s hieroglyphic writing and major innovations in the arts.

By 2650 the power of the pharaoh was absolute and the pharaoh became a “God King”. He (or she - there was one she) controlled the Nile “through the magical powers of his godliness” as well as through the irrigation projects he authorized. As high priest, the pharaoh presided over rituals to assure the cooperation of the Nile and the fertility of the soil. As the powers of the king increased, so did the preparations for his burial. It was during the time of the Old Kingdom that the famous pyramids and the Great Sphinx of Giza were built.

Bad weather for faming…Drought then Flooding

Then the power of the pharaoh to control the Nile failed. Sometime around 2200 BC, the monsoon rains that feed the Nile did not come, crops failed, and the Old Kingdom collapsed. The country descended into turmoil. For a period of about 100-200 years Egypt was ruled by local chiefs who fought among themselves for power.

Finally, around 2065, one of the more powerful chiefs managed to reunite Egypt. Over the next 150 years the successors of this powerful chief again gained total authority over Egypt. This was done partly by overseeing ambitious irrigation projects that were to protect Egypt from another failure of the Nile’s land nourishing floods (remember China?). A canal 300 feet wide was dug to natural depression in the landscape that served are a reservoir which could be filled during the flood season and the water used during the dry season. With food surpluses, Egypt flourished for over two hundred years (the Middle Kingdom) only to be betrayed by the Nile again. This time it was excessive floods. Egypt again descended into chaos. This time famine was aggregated by a challenge from without, migrants and warriors from the south, the west, and the north.

From about 3000 -1000 BC tribes from Arabia and North Africa (Semites) and from the Eurasian Steppes (Indo-Europeans) began to migrate toward the centers of civilization. The warm climate that had precipitated the move towards a state society in Mesopotamia and Egypt had also allowed for an increase in the population of tribal lands around the Near East. When the climate began to cool (carrying capacity fell), these people began to move. These migrations started slowly around 2500 BC and reached a crescendo between 2000-1000 BC. A group of Indo-Europeans moved into Greece and became the Myceneans. Several groups of Semites moved into the lands around Mesopotamia, including one group called the Hebrews who settled in a place called Palestine. Around 1650 BC, Egypt too was taken over by “rulers from foreign lands”, a group of Semite people history calls the Hyksos.

For the next 100 or so years, the Hyksos ruled Egypt from the Delta, extracting tributes from Upper Egypt and building resentments. They adopted the traditions of Egyptians and continued their tradition of divine rule even calling their rulers pharaohs.

Then around 1560 BC, a chief from Upper Egypt challenged the rule of the Hyksos. Using military techniques learned from the Hyksos (horse-drawn war chariots and bows), and some help from Myceane, he expelled the Hyksos and the time of New Kingdom began.

The rulers of the New Kingdom were militarily aggressive and managed to forge an empire far beyond the boundaries of the Old Kingdom including Nubia to the south and Palestine to the North. Egypt became rich extracting tributes from the conquered lands and again built huge monuments, like the Temples of Karnak and Abu Simbel .They buried their dead mummified pharaohs in the Valley of the Kings. In the North, they ran into another group of Semites, the Hittites who had forged an empire as large and as powerful as that of the New Kingdom of Egypt. For many years there was a stand-off at their respective borders. Then in 1200 BC (oops - there is that date again!) the Hittite Empire vanished, the Myceaneans were routed by migrating tribes, and Egypt was about to enter yet another time of turmoil and decline (1070-712 BC).

Next Post: What was going on here?

The Jet Streams

The paths of the Northern and Southern Hemisphere jet streams normally vary according to the season. In each hemisphere, the jet streams gravitate towards their respective poles in the summer and towards the equator in the winter, bringing precipitation as they move. This means that the cool temperate regions are moist in the summer and the warm temperate regions are moist in the winter. This is why both the cool temperate and the warm temperate regions in the Northern Hemisphere, where most of the rain falls on land, are good for agriculture and why most of the first civilizations in the Old World flourished in these climate zones.

The seasonally undulating paths of the northern and southern jet streams are normally consistent for many years. Occasionally, however, they change their course. When this happens, areas once receiving plentiful rainfall may suddenly and inexplicably suffer massive drought, with devastating consequences. In the summer of 1972, for example, the Northern Hemisphere jet stream did not move as far north as usual. The Sahel suffered a severe drought and parts of India had a 60% shortfall in harvest. While some regions receive less rain than usual other receive more and usually at a time they least need it.

Water in the form of rain or irrigation is essential for agriculture of course, but if it rains for too long at one time during the growing season it can be very deleterious especially when plant pathogens are involved. The spores of most plant pathogenic fungi require free-standing moisture to germinate and gain ingress into the host. If plants are not able to dry out between rain storms they are vulnerable to plant diseases. Serious crop losses and famine in ancient Egypt and Rome occurred in growing seasons experiencing unusually heavy rainfall during the growing season.

Next Post: Egypt: The History