Channel 4, 1998


It is one of the central myths of the Old Testament. It provides the basis for the most important date in the Jewish calendar. Its intertwining themes of God's power to smite his enemies and to redeem his chosen people, their escape from slavery and their departure for the promised land, recur throughout the bible. The story of the ten plagues of Egypt and the Israelite exodus under the leadership of Moses is told in the Book of Exodus itself, in Psalms and in the Wisdom of Solomon; it is referred to in numerous places throughout the Old and New Testaments; and it stages a reprise in freshly terrifying form in the "seven last plagues" of the Book of Revelation. Children grow up learning the story; Hollywood film epics celebrate it; it has given succour and hope to people living under the yoke of slavery or oppression throughout history. It is one of the great fables of the Judaeo-Christian tradition -- and, indeed, more widely than that.

But what historic truths lie behind the biblical story of the ten plagues of ancient Egypt? And what scientific explanations for such plagues might accord with the biblical account? This booklet looks afresh at one of the most potent sagas in the canon of religious literature. It examines the evidence for what might have happened in pharaonic Egypt more than three millenia ago. In particular, it tells the story of the attempt by two scientists to get beyond the biblical account and the limitations of previous explanations of the ten plagues by way of a new investigation based on modern epidemiological and other scientific principles.

Dr John S Marr, for many years the chief epidemiologist at the New York City Department of Health, and Curtis Malloy, a research specialist on epidemiology and infectious diseases, did not set out to "prove" or "disprove" the bible story. Rather, they were seeking a rational explanation, based upon what they knew about health and disease in modern-day human populations, for mysterious events that may have occurred in the distant past. That explanation, if it could be achieved, would neither confirm nor refute the central biblical theme of divine agency. For believers in the Old Testament record, it would merely demonstrate the mechanism through which God's will was done. For non-believers, it would show how events described in the bible might relate to actual "plagues" or catastrophes in the ancient world around that time.


There is virtually no historical evidence to support the biblical story of the ten plagues and the Israelite escape from slavery in Egypt. Indeed, there is virtually no historical evidence that there were ever large numbers of Israelites in Egypt at all. Certainly, the biblical description of 600,000 Israelite men (plus women and children) leaving Egypt and wandering in the desert under the leadership of Moses -- as well as defying non-divine considerations of how they might have survived in one of the most inhospitable regions on earth -- seems to have escaped the attentions of ancient record-makers altogether.

The first reference to such a people in Egyptian records occurs in the so-called "Israel Stele" (inscribed monumental stone) or "victory stele of Merenptah", which dates from the fifth year of Merenptah's reign and describes a people called "Israel" who were by then already in Canaan: "Their chiefs prostrate themselves and beg for peace, Canaan is devastated . . . Israel is laid waste, its seed exists no more." Since Merenptah ruled from about 1213-1203 BCE, this is generally taken to mean that the events referred to in Exodus, if they did take place, must have occurred before this date.

There are two principal candidates for the pharaoh who would have been ruler in Egypt if the biblical account were true: Rameses II (the Great), who ruled from about 1279-1213 BCE, and has the distinction of featuring in Cecil B Demille's film epic of the period, The Ten Commandments; and Tuthmosis III, who ruled two centuries earlier, from about 1479-1425 BCE. Biblical scholars and Egyptologists have been unable to resolve the issue, but the Australian scientist, H M Duncan Hoyte, whose research published in 1993 provided an important basis for John Marr and Curtis Malloy's subsequent work, settled on Tuthmosis III. He also proposed that the plagues took place over a ten- or eleven-month period, beginning in July or August and continuing into April or May the following year.

In the absence of any historical record, such attempted chronologies or dating of the Israelite sojourn in Egypt and the ten plagues leading up to their exodus are inevitably speculative. There is, however, one Egyptian document that has been claimed to lend some support to the view that a series of catastrophic events may have taken place in the region during a period compatible with the biblical story. This is an ancient papyrus, the Admonitions of Ipuwer, translated in 1909 by the Egyptologist, Sir Alan Gardiner, and currently held in a museum in Holland. The Dutch physician, Greta Hort, whose 1957 work comprised one of the first attempts at a complete analysis of the possible causes of the ten plagues, used this in support of her contention that the plagues really did occur. Likewise, the Russian author, Immanuel Velikovsky, whose books Worlds in Collision and Ages of Chaos, propose a cometary collision with earth as the underlying cause of the ten plagues, also cited it in support of his theories.

Although written 1,000 years after the plagues would have taken place, the Ipuwer papyrus is an authentic Egyptian document -- and it does describe a series of events that bear a marked resemblance to the biblical plagues: "Lo, the river is blood. As one drinks of it one shrinks from the people. And thirsts for water . . . Lo, all beasts, their hearts shall weep. Cattle bemoan the state of the land . . . Plague is throughout the land. Blood is everywhere . . . Trees are destroyed. No fruit nore herbs are found . . . Lo, the desert claims the land . . . Those who shelter are in the dark of the storm."

The similarity to the biblical plagues could be mere coincidence. Indeed, many similar catastrophes are described in a range of ancient sources from throughout the Middle East. The Ipuwer references could have been derived from the earlier biblical texts -- or from the same original sources as the bible. There can be no definitive conclusions. For John Marr and Curtis Malloy, the question to be answered was: if the ten plagues of ancient Egypt did take place, what scientific explanation might be found for them?


"And the Lord spake unto Moses, Say unto Aaron, Take thy rod, and stretch out thine hand upon the waters of Egypt, upon their streams, upon their rivers, and upon their ponds, and upon all their pools of water, that they may become blood; and that there may be blood throughout all the land of Egypt, both in vessels of wood, and in vessels of stone.
And Moses and Aaron did so, as the Lord commanded; and he lifted up the rod and smote the waters that were in the river, in the sight of Pharaoh, and in the sight of his servants; and all the waters that were in the river were turned to blood.
And the fish that was in the river died; and the river stank, and the Egyptians could not drink of the water of the river; and there was blood throughout all the land of Egypt."
(Exodus 7.19-21)

The Greek historian, Herodotus, called Egypt "the gift of the Nile" because without it the great ancient civilisations that grew up along its banks could not have existed. Today, as in the past, the vast majority of the population -- more than 95 per cent of all Egyptians -- live on the narrow, fertile strip of land on either side of the river or in its delta to the north. The annual ebb and flood of its waters and the rich alluvial deposits which they bring support some of the world's most productive agriculture; the Nile's fish and associated wildlife provide important supplements to the basic diet of the Egyptian people; and the surface of the river remains a vital highway, linking the country over its great length from north to south.

Any threat to the vitality of the Nile, therefore, then as now, was a threat to Egypt itself. It is easy to imagine the devastating effect that the first biblical plague -- the waters of the Nile turning to blood -- would have had on the agrarian society of 3,000 years ago.

So what might this plague have been? Why did the river turn red? And what could have killed all of its fish?

The most common scientific explanation for such a phenomenon has been that it was a product of algae or silt in the river. Alternatively, it has been suggested that volcanoes in Ethiopia -- which would have been active in biblical times -- deposited huge quantities of sulphurous lava and ash into the river, turning its waters red, and making them undrinkable and killing the fish. The Russian writer, Immanuel Velikovsky, has also proposed that red dust from a cometary impact was responsible.

As John Marr and Curtis Malloy were carrying out their investigations into the ancient plagues of Egypt, however, in the spring of 1997 a new environmental disaster was hitting the headlines in the south-eastern United States. Millions of fish were dying in the waterways of North Carolina, their flesh afflicted by deep, open sores. Reports told of the rivers of the region turning red as the disaster unfolded.

So-called "red tides" brought on by algal blooms in sea water are relatively well-known; the algae responsible contain red pigment, which accounts for the water changing colour. Some of these algae are also extremely harmful and toxic to fish, and might result in mass exterminations such as the bible says occurred in the Nile. But until now, Marr and Malloy had come across no references to such blooms in fresh water, which had led them to doubt whether the first plague could be attributed to algae. The news from North Carolina changed all that.

A marine biologist, Dr JoAnn Burkholder, had identified an algae called Pfiesteria, a dinoflagellate, as the organism responsible for the mass fish deaths in the south-eastern United States. She and her team discovered that Pfiesteria secretes neuro-toxins which stun the fish and eat away at their still-living flesh. So far, they have identified a suite of five water-soluble or fairly tissue-soluble toxins that Pfiesteria -- uniquely among dinoflagellates, which don't usually attack fish -- produce to narcotise and kill fish.

If Pfiesteria, or a similar freshwater dinoflagellate, had bloomed in the waterways of ancient Egypt, the combination of the blood from the dying fish and the red pigment that occurs in some strains of the organism, would account for the Nile turning red. And the water, like that in North Carolina, would have become so toxic as to be undrinkable. The North Carolina blooms followed a period of unusually warm weather, linked with the El Nino phenomenon. Environmental conditions had tipped a delicately-poised eco-system into catastrophic imbalance; Marr and Malloy were persuaded that something similar might have happened in ancient Egypt.


"It looks like a biblical plague," said the newspaper report (The Independent, 14 April 1998). "The waters around Hong Kong have succumbed to a scourge known as the red tide, which is gobbling up marine life. This lethal build-up of toxic microscopic organisms has occurred before but never with the vengeance with which it has hit Hong Kong in recent weeks. Sham Cun-hung, assistant director of agriculture and fisheries, said yesterday that it had wiped out 150,000 tons of fish, half of Hong Kong's fish stock, in just four weeks. It is still spreading fast."

So-called "red tides", such as the one that hit Hong Kong with such devastating effect in the spring of 1998, are relatively well-known phemonena. A number of other examples have occurred recently in the Mediterranean and other seas and river estuaries throughout the world. Caused by algae that soak up oxygen and release fish-killing toxins, they are usually short-lived, appearing suddenly in warm, still water but subsiding within two or three days. The combination of excessive sewage discharges, producing nutrient-rich waters, and unusually warm conditions brought about by the El Nino weather phenomenon, however, prolonged this particular red tide, with the resulting devastating impact on marine life.

This was the second biblical-style "plague" affecting a major food source that Hong Kong had suffered in a matter of months -- a reminder that such calamities are not confined to the distant past. The previous December had seen the government order the slaughter of all 1.4 million chickens in the region to contain a still-unexplained outbreak of bird flu.


"And the Lord spake unto Moses, Go unto Pharaoh, and say unto him, Thus saith the Lord, Let my people go, that they may serve me.
And if thou refuse to let them go, behold, I will smite all thy borders with frogs:
And the river shall bring forth frogs abundantly, which shall go up and come into thine house, and into thy bedchamber, and upon thy bed, and into the house of thy servants, and upon thy people, and into thine ovens and into thy kneadingtroughs:
And the frogs shall come up both on thee, and upon thy people, and upon all thy servants.
And the Lord spake unto Moses, Say unto Aaron, Stretch forth thine hand with thy rods over the streams, over the rivers, and over the ponds, and cause frogs to come upon the land of Egypt.
And Aaron stretched out his hand over the waters of Egypt; and the frogs came up, and covered the land of Egypt."
(Exodus 8.1-7)

In seeking a scientific explanation for the ten plagues of ancient Egypt, John Marr and Curtis Malloy believed that they needed to view them as an interrelated series of events. They tried, therefore, to identify a link between the different plagues; and as a first step this involved determining whether, and in what way, a dinoflagellate bloom of Pfiesteria might have caused or created the conditions necessary to bring about the second plague -- of frogs.

At first sight, the link between the first and second plagues seemed straightforward. A mass death of fish would have freed the frogs' spawn from its most important predator, so that unusually large numbers of frogs would have developed into maturity. In turn, these would have been forced away from the toxic waters of the Nile, migrating in great numbers to the land, where they would have died and decomposed. But even in such circumstances, Marr and Malloy questioned whether the frog population could have exploded to the extent described in the bible. They turned to Professor Richard Wassersug, of the University of Halifax in Nova Scotia, for specialist assistance. One of the world's leading experts on amphibians, he had developed his own ideas about the biblical plague of frogs.

"Tsefardea", the word used in the bible to describe the second plague, is a catch-all description for all kinds of frogs and toads. The same word could be used to describe all creatures of this type or it could be used in reference to a specific single species. Wasserug believed that the behaviour of the "tsefardea" as described in the bible best fitted that of toads -- and toads of the genus Bufo, in particular.

Toads of this genus are common throughout the world; and unlike the generally less prolific frog species, they produce huge numbers of eggs -- hundreds of thousands from a single individual. This means that populations of Bufo toads can soar from being relatively rare to numbering many millions. Bufo toads are also drawn towards sources of light and warmth in search of the insects that they rely on for food. The biblical description of how the tsefardea "came upon the land of Egypt", into the houses and bedchambers, the ovens and kneedingtroughs, fits the behaviour of the Bufo toad perfectly. Marr and Malloy were convinced that this was the most likely candidate for the second plague, which came about as a direct consequence of the first.


"And the Lord said unto Moses, Say unto Aaron, Stretch out thy rod, and smite the dust of the land, that it may become lice throughout all the land of Egypt.
And they did so; for Aaron stretched out his hand with his rod, and smote the dust of the earth, and it became lice in man, and in beast; all the dust of the land became lice throughout all the land of Egypt."
(Exodus 8.16-17)

The huge explosion in the frog or toad population was unsustainable. As the bible states, they "died out of the houses, out of the villages, and out of the fields. And they gathered them together upon heaps: and the land stank." Egypt was experiencing the classic symptoms of a suden imbalance in a delicate eco-system triggering off a series of interrelated surges and collapses in the populations of different species. The dinoflagellate bloom killed off the fish; the death of the fish produced a huge increase in the frog and toad population; this was followed by a population collapse, which in turn led to an upsurge in the insect population, which was free to breed unhindered in the absence of an important natural constraint.

But what kind of insects might have produced the third and fourth biblical plagues? For an answer to this question, John Marr and Curtis Malloy again looked towards possible causal links between earlier and later plagues. Might the "lice" and "flies" referred to in the third and fourth plagues be the cause of the cattle murrain of the fifth plague and the boils and blains of the sixth? Many biblical analysts believe that the fourth plague -- of flies -- in the bible story is merely a variant on the third plague -- of lice -- and that they became separated into two different plagues when different accounts were interwoven in the Book of Exodus. Marr and Malloy, however, decided to treat them as separate entities, and they turned to Richard L Brown, known to his friends as the "Mothman", for expert guidance.

Brown, the curator of the Mississippi Entomological Museum and an international expert on insects, pointed out that the taxonomy of insects that we know and use today did not come about until the time of Aristotle's classification of insects, almost 1,000 years after the biblical plagues. He told Marr and Malloy that the original Hebraic word for "lice" (chinnim), as used in the bible to describe the third plague, could refer to any one of about 100 species of insect alive at the time in Egypt. It could also cover arachnids such as spiders, scorpions, ticks and mites. It almost certainly did not mean lice as we understand the term today, however. For a start, the bible referred to them as afflicting both men and beasts, whereas the only lice we know of that afflict human beings do not afflict other animals. A number of possible culprits were considered:

Scabies Originally proposed by J Korzets in a letter to The Lancet, the microscopic scabies mite was rejected by Marr and Malloy as a likely candidate because the term for "lice" used in the bible implies a visible infestation. They noted, however, the suggestion of David J Spencer, former director of the US Centers for Disease Control and Prevention, that the chronic allergic sequela of mite infestation might provide an alternative explanation.

Ticks or maggots Although either of these would have fitted the circumstances pertaining in Egypt at the time, they are too large to merit the usual useage of the term chinnim. They are also unable to fly, a capability implied by the biblical report.

Black flies There are a number of species of black flies capable of transmitting onchocerciasis or "river blindness" in the upper Nile region, which result in dermatosis characterised by intense itching. Again, they are too large to merit the description chinnim and the adverse reactions to their bites take months or even years to appear.

Mosquitoes More than 40 species of disease-transmitting mosquitoes have been catalogued in Egypt; and the Australian physician H M Duncan Hoyte has noted that sciniphes, the Greek alternative to the Hebraic chinnim, translates as mosquitoes or gnats. Once again, though, mosquitoes are relatively large and easily recognised, and would not normally have been described as chinnim.

Midges (also known as gnats or, in US slang, "no-see-ums") and sand flies These tiny flying creatures are bloodsucking flies that fulfill the requirements for the use of the term chinnim. Eight species of midges (Culicoides) and seven species of sand flies (Phlebotomus) have been catalogued in Egypt. Midge larvae, moreover, feed on micro-organisms in decaying organic material (such as dead fish or frogs), and their emergence in huge numbers might indeed be seen as a plague arising from the dust of the land.

Marr and Malloy felt sure that Culicoides canithorax, the biting midge, was the most likely culprit for the third plague. Until recently, though, midges had been considered merely to be irritants (as suggested by the name of one species, Culicoides vexans), rather than the carriers of infectious diseases. Increasingly, however, they have been associated with both human and animal viral diseases. When Marr and Malloy came to research the fifth plague in detail, they came upon evidence that the biting midge was responsible -- confirming them in their judgement that it was the creature referred to in the biblical account of the third plague (see page xx).


"And the Lord said unto Moses, Rise up early in the morning, and stand before Pharaoh; lo, he cometh forth to the water; and say unto him, Thus saith the Lord, Let my people go, that they may serve me.
Else, if thou wilt not let my people go, behold, I will send swarms of flies upon thee, and upon thy servants, and upon thy people, and into thy houses: and the houses of the Egyptians shall be full of swarms of flies, and also the ground whereon they are . . .
. . . And the Lord did so; and there came a grievous swarm of flies into the house of Pharaoh, and into his servants' houses, and into all the land of Egypt: the land was corrupted by reason of the swarm of flies."
(Exodus 8.20-21, 24)

It is hardly surprising that the putrefaction of the river Nile and the mass deaths of fish and amphibians, during that time of the year when the Nile's flood waters would have been receding anyway and leaving behind pools of stagnant water, should be followed by plagues of "lice" and flies. The question was what kind of fly did the biblical account of the fourth plague refer to? John Marr contacted his old professor at the Harvard School of Public Health, the leading entomologist, Andrew Spielman, to narrow down the many possibilities into a shortlist.

There were five viable candidates that might fit both the biblical account and the scientific search for causal links between the different plagues: the horse fly (Tabanus), the house fly (Musca), the black fly (Simulium), the tsetse fly (Glossina) and the stable fly (Stomoxydinae). Black flies were ruled out because they would not be expected to swarm; nor do their populations increase rapidly. House flies and horse flies were also eliminated. House flies might show a sudden, massive increase in numbers in the right conditions, but they would not bite (in the biblical context, the reference to a "grievous" swarm means that they would have caused harm or pain). Horse flies have a very painful bite, but are not usually associated with extraordinary increases in numbers.

This left tsetse flies and stable flies. The bites of both flies often leave open puncture wounds, exposing the victim to secondary infections. Both, therefore, were prime candidates for the fourth plague -- and possible causes of the ensuing fifth and sixth plagues. The tsetse fly, however, is most commonly found in tropical areas of high rainfall, not the dry, arid conditions of northern Africa. As Marr and Malloy began their investigations of what diseases lay behind the fifth and sixth plagues, the most likely vector for these diseases -- and hence the most probable candidate for the fourth plague -- seemed to be the stable fly.


"Then the Lord said unto Moses, Go in unto Pharaoh, and tell him, Thus saith the Lord God of the Hebrews, Let my people go, that they may serve me.
For if thou refuse to let them go, and wilt hold them still,
Behold, the hand of the Lord is upon thy cattle which is in the field, upon the horses, upon the asses, upon the camels, upon the oxen, and upon the sheep: there shall be a very grievous murrain . . .
. . . And the Lord did that thing on the morrow, and all the cattle of Egypt died: but of the cattle of the children of Israel died not one."
(Exodus 9.1-3, 6)

There have been six principal candidate diseases proposed for the fifth biblical plague, which is probably the first-ever written account of an epizootic outbreak -- that is, a disease affecting animals but not human beings. This exclusivity, according to Marr and Malloy, is of crucial significance in determining which disease was responsible for the "murrain", as too is the fact that it appears from the biblical account only to have afflicted certain hoofed mammals. In particular, domestic pets, wild carnivores, birds, amphibians, reptiles -- and goats and pigs, common in Egypt at the time -- all appear to have been spared.

The six major previous candidates for the disease, and Marr and Malloy's reasons for rejecting them, were:

Anthrax A severe bacterial infection that can be spread by biting flies, anthrax would, however, have affected a wider range of animals than those listed in the bible. It would also be expected to have resulted in widespread human fatalities, but that was not recorded in the bible.

Babesiosis A malaria-like disease spread by ticks, babesiosis can afflict all the animals listed in the bible, but different ticks afflict different animals, making it unlikely that a plague would arise afflicting all the different species at the same time. The ticks are also large and easily recognisable, so would have been likely to have been referred to in the biblical account.

Surra A protozoan disease (like the related trypanosomiasis, sleeping sickness, which affects human beings), surra is spread by the bites of both the tsetse fly and the stable fly. The tsetse fly is rarely found in Egypt, however, and surra has not been found that far north in modern times.

Rift Valley fever A viral disease spread by mosquitoes, Rift Valley fever does not affect horses, which are specifically mentioned in the biblical account. It also causes illness in human beings.

Rinderpest and Foot-and-Mouth disease These are airborne viral affections, and Foot-and-Mouth disease in particular is one of the most virulent diseases known. But again neither of them affect horses, and the characteristic features of animals infected with Foot-and-Mouth disease -- that they froth at the mouth and become lame -- would surely have been noted in the bible.

Marr and Malloy were presented with two other possible candidates when they consulted Dr Roger Breeze, director of the US Department of Agriculture Animal Research Centre at Plum Island, off the Connecticut coast. Plum Island, which used to be run by the US military, is a centre for research into some of the most dangerous viral diseases on earth. Breeze, a top animal virologist, first pointed them in the direction of African Horse Sickness. This is a viral disease that affects horses, mules and asses, multiplying in the cells that line blood vessels, allowing blood fluids to get into the lungs and causing the animals literally to drown in their own fluids within a matter of hours. African Horse Sickness does not affect ruminants, but Breeze referred Marr and Malloy to a second, closely-related virus called Bluetongue, which affects cattle, sheep and goats in a similar way.

He also offered an explanation why two such viruses might have been spread so quickly at the same time in ancient Egypt. Both viruses are spread by the Culicoides midge, which Marr and Malloy had already identified as the most likely candidate for the third plague -- of lice. This also offered a possible explanation why animals belonging to the Israelites could have been spared the fifth plague. Culicoides are very weak fliers, and herds and flocks outside their normal distribution range (such as in the Land of Goshen, where the Israelites resided, in northern Egypt) would have been spared their depredations.


"And the Lord said unto Moses and unto Aaron, Take to you handfuls of ashes of the furnace, and let Moses sprinkle it toward the heaven in the sight of Pharaoh.
And it shall become small dust in all the land of Egypt, and shall be a boil breaking forth with blains upon man, and upon beast, throughout all the land of Egypt.
And they took ashes of the furnace, and stood before Pharaoh; and Moses sprinkled it up toward heaven; and it became a boil breaking forth with blains upon man and upon beast."
(Exodus 9.8-10)

Unlike the fifth plague, the sixth -- of boils and blains -- affected both animals and human beings. Previous scientific explanations have included anthrax and a combined staphylococcal/streptococcal bacterial infection. Both of these diseases can be transmitted by flies, direct contact and contaminated food or drink, and both result in the sort of severe skin infections described in the bible. Other theories include babesiosis (but as discussed previously -- page xx -- the variety of different ticks required to carry this disease to different species makes this unlikely) and a general immuno-suppression caused by unidentified mycotoxins, resulting in various opportunistic bacterial skin infections which manifested themselves in blains and boils.

Marr and Malloy proposed a new possibility: Pseudomonas mallei, the bacterium responsible for glanders, a highly contagious infection which can be spread in the air, by direct contact or through fly bites. Used as a biological warfare agent in the first world war and first described by Aristotle in 330 BC, it is known as the "forgotten disease". But in fact it is still found today throughout the Middle East and Africa, affecting both animals and human beings. It spreads via the lymphatic system, causing the lymph nodes to swell and suppurate -- hence the name, glanders -- and fits the description of a plague of boils and blains extremely well. Its most likely carrier would have been the stable fly.


"And the Lord said unto Moses, Stretch forth thine hand towards heaven, that there may be hail in all the land of Egypt, upon man, and upon beast, and upon every herb of the field, throughout the land of Egypt.
And Moses stretched forth his rod toward heaven: and the Lord sent thunder and hail, and the fire ran along the dround; and the Lord rained hail upon the land of Egypt.
So there was hail, and fire mingled with the hail, very grievous, such as there was none like it in all the land of Egypt since it became a nation.
And the hail smote throughout all the land of Egypt all that was in the field, both man and beast; and the hail smote every herb of the field, and brake every tree of the field.
Only in the land of Goshen, where the children of Israel were, was there no hail."
(Exodus 9.22-26)

Even the most violent hailstorm -- albeit one leaving the Israelites unaffected in the land of Goshen -- might not have merited the description of a "plague" had it not followed the six previous, devastating plagues that had hit ancient Egypt in quick succession. But for the disease-stricken Egyptians, with their ruined crops and their dead and ailing livestock, the effect would have been disastrous.

Hail can occur almost anywhere in the world, although storms of such ferocity tend to be associated with hotter regions. The hail stones are ice balls created by updrafts of air which carry water droplets to the top of storm clouds, where they freeze and then fall back down towards earth. They may then be carried upwards again in a succession of updrafts, collecting further water droplets en route and growing in volume each time that they do so. The diameter of the hail stones may range from one or two milimetres to 13 or more centimetres. Even the smallest stones can cause great damage to crops and vegetation; showers of the larger ones can kill or seriously injure animals or human beings caught out in the open.

One such violent hailstorm took place in Israel and Jordan in October 1997. Some 60 people were injured, buildings and vehicles were damaged, and the hail lay more than a metre deep on the ground. In ancient Egypt, a storm of this kind would have caused severe damage to the mudbrick buildings of the Egyptian peasantry, as well as injuring or killing people and livestock who were unable to take shelter. Most devastating of all, it would also have resulted in immense damage to the growing crops at a time when, because of the previous plagues, this agrarian society was even more dependent upon the success of its harvest than usual.


"And the Lord said unto Moses, Stretch out thine hand over the land of Egypt for the locusts, that they may come upon the land of Egypt, and eat eery herb of the land, even all that the hail hath left.
And Moses stretched forth his rod over the land of Egypt, and the Lord brought an east wind upon the land all that day, and all that night; and when it was morning, the east wind brough the locusts.
And the locusts went up over all the land of Egypt, and rested in all the coasts of Egypt; very grievous were they; before them there were no such locusts as they, neither after them shall be such.
For they covered the face of the whole earth, so that the land was darkened; and they did eat every herb of the land, and all the fruit of the trees which the hail had left; and there remained not any green thing in the trees, or in the herbs of the field, throughout all the land of Egypt."
(Exodus 10.12-15)

The most probable culprit for the biblical plague of locusts is Schistocerca gregaria, the desert locust. One of at least nine members of the family Acrididae known to cause serious damage to crops and other vegetation when it swarms, it is found in a belt across northern Africa and the Middle East through to the Punjab. It was clearly well known in ancient Egypt since it appears on various friezes predating the time of the plagues.

The desert locust is far less predictable than other members of the family Acrididae, making it a particularly serious agricultural pest in the areas where it occurs. Relatively harmless in its "solitary phase", when its population density is low, like other locusts it becomes highly destructive in its "gregarious phase", when it swarms in huge numbers. These swarms fly by day in warm weather, descending in vast hordes to consume all living vegetation in the areas they afflict.

Marr and Malloy pointed out that for the ancient Egyptians, a plague of locusts -- coming so soon after the plague of hail, which would have caused great damage to crops and fruit trees already -- would have resulted in a desperate urgency to save whatever they could of their diminished harvest. Partially-damaged crops would have been hastily carried to sheltered granaries and underground storage facilities. These crops would have been dampened and damaged by hail, with no time to dry or sort them before storing. They would also have been contaminated by locust faeces, rich in bacterial and fungal organisms, all of which would have significant implications for the tenth and final plague.


"And the Lord said unto Moses, Stretch out thine hand toward heaven, that there may be darkness over the land of Egypt, even darkness which may be felt.
And Moses stretched forth his hand toward heaven; and there was a thick darkness in all the land of Egypt three days:
They saw not one another, neither rose any from his place for three days: but all the children of Israel had light in their dwellings."
(Exodus 10.21-23)

Before the final plague, which more than any other was to bequeath its mark on future religious beliefs and social practices, the ancient Egyptians were to experience a penultimate "preternatural state of night", in the words of the 19th-century commentator on the biblical plagues, Jacob Bryant. Some analysts have suggested that the darkness was an accompanying feature of the plague of locusts; and certainly modern-day swarms of locusts can be so dense as to farm dark clouds as they fly and plunge the areas onto which they descend into an intense gloom. The Russian author Immanuel Velikovsky's cometary-collision theory for the biblical plagues, meanwhile, proposes "gravel" and dust from the comet's impact as the cause of the darkness. Similarly, the theory that a volcanic eruption may have lain behind the ten plagues would also account for it.

Marr and Malloy, however, preferred Greta Hort's suggestion that the darkness was produced a khamsin, a hot southerly wind sweeping in from the Sahara. This wind can produce fierce sandstorms during the khamsin-season (from March to May). Typically lasting for two or three days, such as one that struck Cairo in the spring of 1997 while Marr and Malloy were conducting their research, these storms have been known to bury entire buildings and large monuments in fine sand, blotting out the sun in a dark, dusty haze. The massive sand drifts that can accumulate in the lee of buildings in such storms would have blocked entrances, preventing the inhabitants from entering or leaving until the storm subsided, as described in the biblical account. Past storms of this nature are one of the reasons for the preservation of ancient tombs and other monuments that in some cases have remained buried for several thousand years in Egypt before their discovery by modern archaeologists.

The likelihood that the plague of darkness was the product of a khamsin sandstorm was given added weight by the fact that the biblical timetable required the ninth plague to have taken place in March. Marr and Malloy noted that the first of the khamsin storms each year, taking place around this time, would also have been the worst, picking up all the accumulated fine sand from the previous year.


"And the Lord said unto Moses, Yet will I bring one plague more upon Pharaoh, and upon Egypt; afterwards he will let you go hence . . .
. . . And Moses said, Thus saith the Lord, About midnight will I go out into the midst of Egypt:
And all the firstborn in the land of Egypt shall die, from the firstborn of Pharaoh that sitteth upon his throne, even unto the firstborn of the maidservant that is behind the mill; and all the firstborn of beasts.
And there shall be a great cry throughout all the land of Egypt, such as there was none like it, nor shall be like it any more."
(Exodus 11.1, 4-6)

The tenth and final plague, as well as being the most shocking and the one that would leave the biggest mark on future social and religious beliefs and practices, also poses the biggest mystery scientifically. What kind of scientific explanation might account for something that affected only the firstborn -- both of animals and human beings? Was it possible to square the biblical story with modern-day scientific knowledge?

The bible provides surprisingly scant details of this, the most terrible of all the plagues, focusing its attention more on the measures that the Israelites were required to take to avoid being affected by it themselves. This is almost certainly a result of the importance attached by the Priestly (author "P") account of the plagues in Exodus to establishing some of the fundamental principles and rituals of the Judaic faith (see page xx). It has also led many commentators to focus upon explaining the tenth plague as a consequence of the cumulative effect of the previous nine plagues, rather than as a separate "plague" in itself.

Greta Hort, for example, saw it as no more than a famine brought about by the destruction of the Egyptian's crops (wheat, barley, emmer, spelt and fruit) and meat and fish supplies. This was exacerbated, in her view, by the deaths of beasts of burden and the coverage of arable land by the khamsin-induced sandstorm, which severely curtailed their ability to till the land and grow replacement crops. Hort also suggested that the biblical reference to the death of the "firstborn" might better be translated as the death of the "first fruits" -- that is, the fresh sprouts of crops that had emerged following the earlier plagues -- presumably as a result of the sandstorm.

Other explanations for the tenth plague included Velikovsky's suggestion of an earthquake brought about by a cometary collision, the after-effects of a volcanic eruption, and the spread of anthrax or other diseases. Hoyte, in particular, suggested that contaminated foodstuffs at a time of general shortage could have resulted in widespread poisoning. Specifically, he argued that typhoid fever (Salmonella typhi) and salmonellosis (Salmonella typhimurium) were likely candidates. The former affects only human beings, but the latter affects animals as well.

Marr and Malloy remained unconvinced, however. Both of these infections can cause death, but only after many days or weeks of illness -- certainly not with the sort of immediacy described in the biblical account. Nor did any of the previous theories about the tenth plague explain why it would have had a differential impact on the firstborn. The two men continued their search for an explanation that would fit in as closely as possible with what was described in the bible. In this instance, the very absence of detail in the biblical account persuaded them against a natural disaster (such as an earthquake) that would have merited separate description in its own right or a non-immediately acting infectious disease (such as typhoid, salmonellosis, babesiosis or anthrax). They turned again to their view of the ten plagues as an interrelated, causative process. What, among the cumulative consequences of the preceding nine plagues, might have led to the tenth?

The two scientists conducted a review of the preceding plagues and their consequences. This was what they had to work with:


  • The first plague makes the Nile and the associated water supplies of ancient Egypt undrinkable.
  • Stocks of fish, an important supply of protein in the local diet, are wiped out, and even months later, like the water, are considered suspect.
  • Frogs -- or toads -- after an initial population explosion, also die, polluting the water and land with their corpses, and allowing insect populations to increase unhindered.
  • Explanation: A dinoflagellate bloom that deoxygenates the waters and produces noxious toxins.

  • The availability of animal protein from cattle, sheep, goats and swine is greatly reduced (or that which was available is made suspect) through illness and disease.
  • Beasts of burden, such as horses, donkeys and oxen, are afflicted, harvests left untended and fields left untilled.
  • Explanation: African horse sickness and bluetongue, viral diseases transmitted by the Culicoides midge, and glanders (Pseudomonas mallei), transmitted by Stomoxys calcitrans, the stable fly.

  • Field crops are destroyed by hail and water, left to rot, or picked in haste.
  • Locusts consume the remaining vegetation, particularly young shoots that might have offered hope of new crops.
  • A sandstorm covers all obvious remaining sources of food supplies, and provide a blanket of warmth, humidity and darkness for water-soaked foodstuffs beneath the sand to rot.
  • Explanation: Hail, locusts and a sandstorm induced by a khamsin, a hot southerly wind coming from the Sahara.

  • The 2.5 million people of ancient Egypt are starving after ten months of misfortune.
  • A mysterious illness then kills the eldest Egyptian in each family and the eldest of animals in a sudden catastrophe, without any apparent cause other than God's will.
  • Explanation?


It was Curtis Malloy who hit upon what the two scientists hoped might prove the key to explaining the tenth plague -- the locusts' faeces, which would have contaminated what remained of the Egyptians' crops as they rushed to save what they could. What organisms might the locusts have introduced that would thrive in the damp, foetid conditions of the Egyptians' stores?

The answer was mycotoxins. Mycotoxins are chemical compounds produced by fungi while growing on organic substances, such as corn and other crops. The fungi themselves are not harmful, but the mycotoxins they produce as by-products can be extremely so.

Around the time that Marr and Malloy were carrying out their research, they became aware of a series of mysterious child deaths in the Cleveland area of Tennessee. Eduardo Montana, of the Atlanta Center for Disease Control, had been called in to investigate. When he began his investigation, an eight-week-old boy had just become the 33rd Cleveland baby in four years to be diagnosed with Pulmonary haemosclerosis, a rare lung disease that is believed to be caused by a toxic black mould or fungus found in water-saturated wood and paper materials. Montana and his colleagues conducted surveys of the babies' homes; in each case, they found significant water penetration in the basements and, associated with it, a black, slimy mould.

It wasn't the mould itself, Stachybotris atra, that was responsible for the babies' illness, but a mycotoxin carried on the fungal spores. It is thought that this airborn poison enters the bloodstream of its victims through the lungs, where it causes capillary bleeding. The mycotoxin released by the mould, although known to cause disease in animals, had not been associated with human ailments before. But since its identification by Montana in the Cleveland cases, it has been linked to a number of other mysterious human illnesses in places where the same sort of conditions -- damp, decaying buildings in poor, often inner-city areas -- occur.

In ancient Egypt, there would not have been fungal growths in damp, poorly-ventilated basements, but there would have been moulds growing on hastily-gathered, damp grain in unventilated, sand-covered stores. The conditions most favourable for the growth of some of the major mycotoxin-producing fungi were all present in those stores. Recent research in the southern US, for example, has found that one of the most important mycotoxin-producing fungi grows best in a temperature range of 80-110 degrees Fahrenheit, a relative humidity of 62-99 per cent and a kernel moisture content of 13-20 per cent -- all of which are likely to have been found in the ancient Egyptians' grain stores.

The US scientist, R Schoental, had been the first to suggest that mycotoxins in contaminated foodstuffs might explain the sudden deaths of ancient Egyptians and their animals in her essay, Mycotoxins and the Bible, in 1984. She also proposed a possible reason for its preferential impact on the firstborn -- that the most dominant animals and human beings would have had first access to the stored food supplies, and so they would have been most affected by the fatal toxins.

Marr and Malloy took Schoental's speculation further, however, by looking at the specific nature of those food supplies, the specific mycotoxins that might infect them and the specific cause of death in those who came into contact with the toxins. More than 100 toxigenic fungi have been identified since the first mycotoxin was discovered in 1961 (after 100,000 turkeys died in Britain when they were fed mouldy peanut meal), and several dozen mycotoxins have been found to be responsible for illness in animals and human beings. Only a small number, however, are linked to moulds that grow on the sort of crops that would have been in the ancient Egyptians' stores. The most toxic among these include the mycotoxins, macrocylic tricothecenes, produced by Stachybotrys atra -- the mould identified as responsible for the babies' deaths in Cleveland.

Stachybotrys atra grows on cellulose -- where it was soaked paper or wood in the Cleveland basements, it might have been grain and cereal crops in ancient Egypt. The macrocylic tricothecenes it produces have been linked to animal deaths in many countries worldwide and to the deaths of thousands of people as well as animals in the USSR during the second world war. As Marr and Malloy now knew from the Cleveland cases, the toxins could be carried on airborn fungal spores as well as being ingested directly. They also noted that ruminant cattle are particularly attracted to damp straw, on which the fungus grows especially well. Very small quantities of these toxins are known to cause illness and death; larger amounts can very quickly lead to massive internal bleeding in the lungs or gastrointestinal tract, causing sudden death. The need of the ancient Egyptians to use improperly-stored, mouldy grain to avert the threat of starvation might well have precipitated widespread illness and death from mycotoxin poisoning.

But even if these mycotoxins were responsible for the tenth and final plague, what might explain the differential impact on the firstborn? Here Marr and Malloy further developed Schoental's speculative suggestion.

They surmised that the first people to have had access to the contaminated stores of grain and foodstuffs would be have been older, more responsible or more powerful individuals in Egyptian society. They would also have been the first to eat bread produced from the mouldy wheat; indeed, there is a strong ancient tradition, mentioned in the bible, whereby the firstborn should not just be fed first but receive double rations of what food is available. Similarly, the first animals to feed would be the most dominant ones -- typically the eldest. Mycotoxin poisoning could have occurred by breathing in the unventilated air from the grain stores or by eating the food prepared with the contaminated grain. Symptoms of the poisoning would have been quickly noticeable, which might have alerted other people to the dangers from the contaminated grain. In addition, deeper stores of grain and foodstuffs may not have been so affected by the surface-growing mould, sparing humans and animals who fed off it later. The grain stores themselves, moreover, would have been ventilated by this stage, removing the threat of exposure to airborn toxins.

The Israelites could have escaped the worst effects of mycotoxin poisoning, firstly, because the Land of Goshen, where they lived, escaped some of the earlier plagues that exacerbated the food shortages and famine in the rest of Egypt. And secondly, it may be that the tradition of the Passsover meal (see page xx), in common with other dietary injunctions found in the bible, bears some relation to ancient understanding of food hygiene and safety. The key elements of that meal -- new-born lamb, herbs and unleavened bread -- are all safe from mycotoxin contamination. Is it possible that this was a means of reinforcing by religious myth some basic principles of good dietary practice?

The bible also contains detailed injunctions on how to deal with the presence of certain kinds of mould in dwellings. And a recently decoded fragment from the Dead Sea Scrolls, Cryptic B, apparently passed down from Moses's teachings, contains an instruction for Jews to destroy any dwelling in which mildew was found. The ancient peoples of biblical times would not have know what mycotoxins were -- but was it possible that they knew of their effects, and as part of their religious practices counselled methods of avoiding them?


In seeking a rational and historical basis for one of the great sagas of ancient times, as it is described in the bible, we do not necessarily cast doubt upon the underlying message of faith in an all-powerful God. Nor is this only some kind of long-distance detective work to unravel an ancient mystery. Roger Breeze, of the US Department of Agriculture Research Service, when he looked at the explanation put forward by John Marr and Curtis Malloy for the ten plagues of Egypt, told Channel Four's Equinox programme-makers that:

"What strikes me is that it's not just a series of unrelated events, but a related series of environmental plant and animal catastrophes that culminate in a very, very serious human health problem that affects society as a whole. People like myself, who work in the USDA and other government organisations, are well are that these diseases are with us today. We need to be eternally vigilant to make sure that we protect our societies against these epidemics because the systems that are in place around the world to provide disease surveillance and control are very fragile and they are under incredible pressure from old threats and new problems."

Perhaps the most significant outcome of John Marr and Curtis Malloy's research into the ten plagues of ancient Egypt is not what it tells us about the past, but the lessons it holds for the present and our future.

Table: Summary of different explanations suggested for the ten plagues of Egypt


Currently the medical director of a large health maintenance organisation in Connecticut, John Marr was previously a major in the US Army, and for many years the principal epidemiologist for the New York City Department of Health. He has published more than 50 papers on various infectious disease topics and lectured on communicable diseases throughout the US. In 1977, he wrote The Black Death, a novel about an outbreak of pneumonic plague in New York. Recently, he co-authored The Eleventh Plague, a medical bioterrorist thriller based on his research into the scientific causes of the ten plagues of ancient Egypt.

Marr's interest in the Egyptian plagues went back many years, and for him it meant more than just unravelled a biblical enigma. In a world facing new "plagues" all the time, he was seeking fresh insights from old stories into how diseases arise and spread. Previous investigations had tried to account for individual plagues in the biblical story. But no one had tried to analyse the ten plagues as an interrelated whole -- an approach that was central to his work in public health. He wanted to bring together the historical and religious record with the whole range of modern scientific disciplines -- epidemiology and epizootiology (the study of the occurrence of disease in human and animal populations), entomology (the study of insects), microbiology (the study of microbes), toxicology, marine biology, and so on.

He chose as a partner for this project Curtis Malloy, a research associate with the Medical and Health Research Association of New York City. With a brilliant Master of Public Health degree from Columbia University and a taste for the offbeat and bizarre, Malloy was an ideal choice. An accomplished juggler in his spare time, he was to have no problem in juggling the various scientific disciplines that the research called upon. His own specialisms, which include international health, epidemiology, infectious diseases and entomology, were also precisely what was required for Marr's project.

In 1996, the two men founded plaguescape.com, an internet version of the academic paper they co-authored detailing their researches into the possible causes of the ten plagues of ancient Egypt. Plaguescape was awarded the highest ranking of web sites by the Encyclopaedia Britannia. The web site has been continually updated as their research has progressed, and in 1998 they collaborated in the production of the Channel Four Equinox programme, The Ten Plagues of Egypt, which this booklet was produced to accompany. John Marr's latest project, meanwhile, has involved him in exploring a novel new hypothesis to explain the cause of the 1576-81 epidemic that essentially destroyed the Aztec civilisation.


One man dominates the Old Testament books of Exodus, Leviticus, Numbers and Deuteronomy -- Moses. So much so, indeed, that the traditional belief was that he had written these four books -- and the preceding one, Genesis -- himself. The Book of Exodus starts with the story of how the Israelite descendants of Jacob, who had settled in Egypt and become more prosperous than the Egyptians themselves, were put into slavery by their jealous Egyptian overlords. When this fails to slow the growth in the Israelite numbers, the Pharaoh, the Egyptian ruler, orders the killing of all sons born to them. Moses (the word is actually Egyptian for "son", a shortened version of names such as Thutmosis) is saved when he is hidden in a basket of bulrushes among the reeds on the banks of the Nile. Here he is found by Pharaoh's daughter, who agrees to an offer by Moses's sister, Miriam, to find a Hebrew nurse for him. The nurse Miriam provides is Moses's mother, who thus brings up her own son.

Moses grows up in the Pharaoh's household, but as a young adult he kills an Egyptian for beating a Hebrew. He flees to Midian, on the east of the Gulf of Aqaba, where one day, on Mount Horeb modern-day Mount Sinai), God appears to him in the form of a burning bush. God reveals his name to Moses as Yahweh and orders him and his brother Aaron to lead the Israelites out of slavery in Egypt and into the "promised land" of Canaan. Yahweh tells Moses to go to Pharaoh and demand that he "Let my people go".

The first time Moses and Aaron go to Pharaoh he is unimpressed and merely increases the burden of the Israelite slaves. On the second occasion, Aaron turns his staff into a serpent in front of Pharaoh; Pharaoh's magicians do likewise with their staffs; and then Aaron's staff swallows up theirs. But Yahweh had "hardened Pharaoh's heart, that he hearkened not unto them"; he refused to set the Israelites free. And so began the sequence of the ten plagues of Egypt, following each of which Pharaoh either refused to relent and let the Israelites go or he appeared to do so for a while and then "hardened his heart" once again.

First came the turning of the Nile's water to blood. Then, in succession, the land of ancient Egypt was beset by plagues of frogs, lice, flies, a murrain of cattle, boils and blains, hail, locusts, darkness and, finally, the death of the firstborn. Only at the last did Pharaoh finally relent and let the Israelites go. Even then, he changed his mind soon afterwards and sent his soldiers in pursuit; the Israelites made their escape through the miracle of the parting of the waters of the Sea of Reeds.


"For I will pass through the land of Egypt this night, and will smite all the firstborn in the land of Egypt, both man and beast; and against all the gods of Egypt I will execute judgement . . . And the blood shall be to you for a token upon the houses where ye are: and when I see the blood, I will pass over you, and the plague shall not be upon you . . . "

Passover, or the feast of unleavened bread, is the central event in the Jewish calendar. In the biblical account of the tenth plague and the exodus from Egypt, Moses was commanded by God that, on the evening of the 14th day of the month of Nisan (in March or April), each Israelite family should slaughter a male lamb and smear its blood on the lintel and posts of the doors to their houses. This was to be a sign to the angel of death to pass over the homes of God's chosen people when the tenth plague, the killing of the firstborn, struck. The biblical injunction was that the lamb should be roasted and eaten whole with bitter herbs and unleavened bread. "And thus shall ye eat it," the instruction continued. "With your loins girded, your shoes on your feet, and your staff in your hand; and ye shall eat it in haste: it is the Lord's passover."

Although only the most devout Jews may follow these, and other, biblical instructions relating to the occasion to the letter today, Passover is still commemorated every year in Jewish homes. The occasion is marked by a ceremony called the Seder, at which the slaughter of the lamb is symbolised by the display of its shank bone. The bitter tears of the Israelite slaves in Egypt are represented by a bowl of salt water. A fruit paste represents the mortar they were compelled to mix in their work as slaves on Pharaoh's monumental building projects. And the escape from slavery is symbolised by the baking of matzot, unleavened bread, which would have been taken with them as sustenance during their flight from Egypt.


In common with a great deal of the bible, the Old Testament Book of Exodus, which contains the principal account of the ten plagues and the Israelite escape from slavery in Egypt, is not a single narrative by one author but several different accounts brought together into one. The story of the plagues themselves (Exodus chapters 7-12) consists of three intertwined versions, probably separated in their date of final composition by as much as seven centuries from the events they are purportedly reporting. The Yahwistic (J) and Elohistic (E) sources -- so named after the linguistic preference of their authors for referring to God as "Yahweh" or "Elohim" -- comprise the earlier accounts, possibly originally written close to the time of the reported events, onto which has been added later Priestly (P) material. The Book of Exodus -- together with the other first five books of the Old Testament -- was almost certainly put together when the Priestly material was added. The majority of biblical scholars now believe that this was most likely to have taken place around the time of the Israelite captivity in Babylon (592-539 BCE).

Interestingly, none of these sources include all ten of the plagues. J lists eight, leaving out the third (lice, or gnats) and the sixth (boils). E mentions the first (the Nile turning red) and then jumps to the seventh (hail). And the Priestly account refers to the first three, the sixth and the tenth.

It is also noteable that only some of the plagues are described as affecting exclusively Egyptians. While the biblical account refers specifically to the Israelites as being spared the fourth, fifth, sixth, seventh and ninth plagues, Egypt as a whole (presumably including the land of Goshen, where the Israelites resided) was said to be afflicted by the first, second, third and eighth plagues.


Maps, as we understand them today, did not generally exist in ancient times. Indeed, there is only one known surviving map from almost 3,000 years of pharaonic Egypt. This is a fragment of a sketch map, now in the Museo Egizio, Turin, which probably shows the location of quarries and gold mines in the Wadi Hammamat. Given the absence of any hard historical evidence for the Israelites having been in Egypt at all (see page xx), moreover, locating the likely position of any settlements is at best the subject of some debate.

We do know that the ancient city of Memphis, just south of modern Cairo, was the main residence of the pharaohs and centre of the Egyptian state during the period when the ten plagues would have happened. And most biblical scholars agree that the Land of Goshen, where the bible says the Israelites resided, was somewhere northeast of this, near ancient Heliopolis. This would fit in with the generally accepted route of the Israelite exodus, as described in the bible and marked on the map, including the initial escape through the parted waters of the "Red Sea" (now accepted by most scholars as a mistranslation of "Reed Sea", describing a marshy extension of the modern-day Red Sea along the line of the Suez canal).

Although required to carry out slave labour for their Egyptian overlords, the Israelites lived separately from them, according to the bible. This georgaphical separation might provide a rational explanation why they were spared some -- though not all -- of the ten plagues.

Table: Summary of different explanations suggested for the ten plagues of Egypt