Part 1 of 3

Brad Sparks

Naturalistic theories of the Ten Plagues attempt to account for the miraculous events of Moses and the Exodus of the Israelites from Egypt using natural phenomena in an exotic biological chain reaction of red algae, anthrax and various other epidemic pathogens and insects, plus flood water, red river mud, and/or wind. These Plague theories have been widely and uncritically accepted among Biblical scholars, and believed quite mistakenly to be scientifically established, but they are virtually unknown and undocumented in the scientific community. Such theories have escaped serious scientific scrutiny until now. The leading “natural phenomena’” theories of the Plagues are reviewed in-depth here for the first time and found to be fatally flawed, the main one so lacking in scientific merit that it has the appearance of an elaborate hoax even though most likely proposed with the utmost sincerity (Hort 1957, 1958).

Why are naturalistic theories so popular? For some, they avoid complete skepticism of the Bible on the one hand and complete supernaturalism by Divine miracle on the other. This middle ground asserts that the Bible is correct that these events really did occur, but as natural occurrences under unusual conditions, not as miracles. Such a theory is attractive to those who presume that it actually provides a kind of stunning scientific proof of the Biblical account of the Ten Plagues. According to many conservatives the miracle involved is one of soft subject data of timing and severity, or of otherwise scientifically acceptable “natural” phenomena. Part of the problem may be linguistic. Disease epidemic theories rely to some degree on a misnomer. The Biblical word “plague” in English suggests only infectious disease when the actual Hebrew word and variants translated from Exodus chaps. 9–12 (nega’, negeph, magephah) refer more broadly to “sharp blows” and “calamity,” not just disease (Brown, Driver, Briggs 1979:550a, 619a–620a-620a).

Hort’s Red Algae-Anthrax Theory

The most popular naturalistic theory of the Plagues of Egypt began in 1957 with Greta Hort, a scholar of medieval English literature and religion, who published a theory explaining the Plagues as an interconnected series of catastrophic natural events. This “ecological domino” effect (van Biema 1998:4) started with a Plague of Blood consisting mainly of a massive “red tide” of algae in the Nile River plus red mud (Sailhamer 1992:254; Kitchen 1962; Cole 1973:90; Elwell 1988; Humphreys 2003:114–18, 125, 144). Then anthrax bacteria in the river infected animals and humans. Every succeeding Plague is seemingly accounted for by Hort. Hort’s theory has become highly respected and is “widely cited” (Huddlestun 1992:1109) in numerous encyclopedias, commentaries and Biblical reference works though never subjected to any independent scientific review until now. As it turns out, her complex scheme is wracked with insuperable scientific, historical and factual difficulties. Her theorized algae cannot survive and do not naturally occur in the Nile or Egypt, are the wrong color, are utterly harmless not toxic, and anthrax does not infect rivers, just to list a few of the many scientific blunders made by Hort.

Hort claims that this biological chain reaction began with one of two species of red algae in a Nile source, Luke Tana in East Africa. But this claim is complexly wrong, mistakenly documented only with a passing remark in a two-volume microbiology work about the algae occurring in Europe—not Africa (Hort 1957:94, fn. 19, citing Gessner 1955:412–13; Beegle 1972:101). Hort’s algae, Haematococcus pluvialis and Euglena sanguinea, are not even red or bloody in color but are green in flowing water, thus could not possibly have caused a red plague of “Blood” (they turn red only when dry or desiccating which is an absurdity in the Nile). Scientists have never seen any sign of Hort’s algae “naturally occurring” in the Nile or East Africa, not even in microscopic trace amounts.1 Yet the beauty of Hort’s theory is thought to be in its purported ability to explain how a normal “natural” phenomenon (algae) can cause a catastrophe such as the Plagues under certain natural conditions.

Hort’s culprit algae species are so far from being the cause of a deadly “‘plague” that they are actually used today as human and animal food supplements worldwide, one species of which the present author has personally tested as safe. Neither species is toxic or even a water pollutant rendering water undrinkable or unfit for consumption, as will be detailed below (Palmer 1980:66, table 19).

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Haematococcus pluvialis is green not red, contrary to Hort. It will turn red only when drying out.

The attractiveness of Hort’s theory lies in its attempt to interlink nine if not all ten of the Plagues in a “scientific” cause-and-effect chain of natural events, each of which causes or contributes to the next or a succeeding Plague with only a few out-of-order exceptions.2 Hort believes she has proved that each Plague arose as a direct or indirect consequence of just “one specific natural phenomenon”—the abnormally high rise of the annual Nile flood (Hort 1957:85, 1958:58). One set in motion by the severe rains and the purported melting snow (an old myth: Lloyd 1976:92–93, 101–102) at the sources of the Nile, Hort says each Plague followed their inevitable natural sequence and geographic coverage in her catastrophic domino theory, a unified series of about eight to nine months’ duration. They fit exactly the natural phenomena of Egypt in exactly the correct order, Hort claims. These natural events also supposedly account for the pattern of some Plagues seeming to affect all of Egypt, some seeming to avoid the Israelites’ land of Goshen, some that halted abruptly and some that apparently tapered off.

Hort’s discussion would lead an unsuspecting reader to believe that her algae are well known to scientists and are a major constituent of the Nile flora. But the shocker is that her algae are actually nonexistent entities in Egyptian and East African biology. Exhaustive scientific studies have cataloged more than 400 species of algae in the Nile, and some 1,000 species in East Africa including Hort’s alleged Lake Tana source, yet scientists have never found these two algae species there (Brook 1954; Talling and Rzóska 1967:644; Brunelli and Cannicci 1940; Rzóska 1976:210, 229, 266, 268; Talling 1967b: 387–88, 390, 392; Hammerton 1972:187–88; Grönblad, Prowse and Scott 1958; 1–82; Grönblad 1962:3–19; Mshigeni 1983; Institut Royal 1952, 1954, 1955). Hort does not bother to discuss the actual dominant natural algae of the Nile, which are not red but green (Anabaena flos-aquae and Microcystis flos-aquae) and/or colorless (Melosira granulata), and there is no mention or even an allusion to them in Hort’s 32-page paper, which had a year in between publication of its two parts to catch any egregious errors or omissions. No biologist has ever reported a red bloom of any kind of algae in the Nile or its headwaters, let alone of Hort’s algae (Rzóska 1976; Palmer 1980). No photographs of a Red Nile appear in scientific texts, Bible reference works, or travel guides despite the popular interest they would generate if a “Blood” Nile were truly a natural occurrence. Hort’s algae do not naturally occur in the Nile or East Africa. In fact, these harmless algae are never known to cause a Harmful Algal Bloom (HAB) or water pollution anywhere in the world in the relatively few places they do occur (see below on UNESCO database) (Palmer 1980).

The reason why Hort’s algae do not occur in the Nile or in East Africa is simple: Hort’s algae are rare and fragile ice water species that belong in sub arctic cold climates, are used as “industrial indicators” of snow and ice water temperatures, and can barely survive even in their own ideal environment (Pringsheim 1966:1–2, 5; Palmer 1980:72, table 23). It is a biological impossibility for these algae to survive, let alone thrive, in the Nile, a tropical habitat that is actually deadly to algae of all kinds for a number of reasons, including the universal algae-killing effect of silt. Instead, Hort maintains the fiction that the algae “would appear only at a time when the Nile was at its highest” (Hort 1957:94, emphasis added). Hort never tells the reader the well-known fact, known for centuries and confirmed microscopically by biologists, that the silt-laden Nile at its flood time high is completely clear of all algae of every species (Bryant 1810:79:84; Brook 1954; Hammerton 1972:195, fig. 7).

Surely the most scientifically discrediting of the long list of Hort’s scientific errors arises from the well-known elementary fact that plants need sunlight for photosynthesis (Palmer 1980:18; Round 1981:27 and fn.). Algae are plants. Yet her theory requires massive loads of intensely dark silt that would black out the sun in the water—as it later does in the air, when dry, to create the Plague of Darkness claimed by Hort. Such a silt blackout would kill her plant algae. This algae-killing effect is well known to scientists studying the Nile, and will be discussed in detail in Part 3. It is also common knowledge even to laypersons that algae grow in stagnant ponds, and red tides are found in the ocean, environments very unlike the Nile.3 Anthrax is soil-based and not found in the Nile either. Nor is anthrax red in color.

According to Hort’s theory, each Plague recounted in the book of Exodus occurs in the correct “natural” sequence, all triggered by one underlying cause—a single and extraordinarily severe occurrence of the annual Nile flood in July. This torrent allegedly washed down a massive load of “red” mud along with the main reddening agent, the red algae, which discolored and contaminated the water in a red tide (or HAB as biologists now prefer to call it). The supposedly red mud-red algae combination together created an even more red Plague of Blood. Red algae are crucial to Hort to make the water “truly blood-red” (Hort 1957:87, 94, passim.)

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Then followed the deadly chain reaction of successive Plagues, says Hort. The algae killed the fish. Dead fish developed anthrax, sickening the frogs and driving them ashore. Dead frogs contaminated the soil, infecting and killing livestock animals with invested internal anthrax. Biting flies proliferated in the decaying plains left by the heavy flooding, then carried the especially virulent skin anthrax from dead cattle to the live cattle and humans, causing the Plague of “boils.” The severe weather that had caused the unusual torrent then brought hail and locusts. The excessive load of mud from the high Nile flood dried into an unusually heavy covering of powdered silt. A violent dust storm lofted the silt into the air, creating an extraordinary darkness. The first fruits of crops were destroyed—rather than firstborn children—in the final Plague according to Hort, claiming an error in the translation of the Biblical account. Some of the Plagues may have missed the Israelites due to a natural sheltering effect of the Wadi Tumilat valley, east of the Nile Delta, in which they supposedly dwelt. Hort suggests the Israelites left Egypt because they had food the Egyptians wanted and would have taken from them, so if they stayed they would “die either by violence or starvation.”

Hort’s theory is seemingly quite convincing—but only on the surface. Overlooked by a generation of scholars is the passing admission by Hort that the algae connection itself, the central core of her entire theory, is a total “supposition” (Hort’s term) in the first place (Hort 1957:94). The impressive-looking recital of formal Latin binomial species names of the alleged “blood plague” algae, and the recounting of numerous alleged facts of biology and geology have all worked together to make her case seem to the unwary to be established scientific fact. But Hort’s case is not the summation of some vast body of biological evidence or the accumulated wisdom of many lifetimes of dedicated scientific study. It is based on one single microbiology reference she has completely misinterpreted or misrepresented. Her case for these two algae strains, Haematococcus pluvialis and Euglena sanguinea, is built on that one passing reference, which, as already mentioned, does not even document these algae occurring in the Nile, but in Europe.4

It is thus all the more disturbing to read that Hort’s key to solving the problem of the Plagues, which she insists is absolutely essential to her theory, is her admitted mere supposition that one or two of the allegedly “red” algae species actually came down from Lake Tana along with masses of “red” mud. Hort asserts we can only

suppose that the waters of the Blue Nile…had brought them [the two species of “red” algae] into the Nile from Lake Tana (Hort 1957:94, emphasis added).

In other words Hort has no scientific or historical evidence that these algae did enter the Nile from Lake Tana; she can only “suppose” they did. There are no citations of scientific or historical literature here, no evidence whatsoever. A generation of scholarship assuming a natural origin for the Plagues rises or falls on this half-sentence guesswork that is contradicted by all scientific surveys of the continent, including the Italian expedition to Lake Tana in the 1930’s (Brunelli and Cannicci 1940), of whose findings Hort should have been aware. The ensuing events in the alleged chain reaction also strain our credulity. Hort claims that a heavy bloom of algae caused anoxia, supposedly consuming and cutting off the oxygen in the flood-stage Nile and thus killing masses of fish that normally feed on frogspawn. This led to a population explosion of frogs invading the land, they dying mysteriously from anthrax, she asserts. But anthrax is a soil contaminant, not a river pollutant. Algae usually generate a net increase in oxygen and thus cleanse the water (Palmer 1980:3–4, 21). And it is a physical impossibility for algae to remove all oxygen from the Nile’s well-aerated turbulent waters at flood time (see Part 3) (Talling 1976a: 371–74; North Carolina State University 2003).5

Anthrax cannot infect dead fish or live frogs, contrary to Hort’s claims (Marr and Malloy 1996:12–13; this theory of the Plagues goes back to 1890 [Blanc]). Anthrax only infects mammals, typically grazing herbivores such as sheep, cattle and goats, and does not infect frogs, amphibians, reptiles or fish (Marr and Malloy 1996:15; USDA 2001; AVMA 2001; Cunha 2001; UN FAO 2001). Anthrax is soil-based and is not contracted from large bodies of water such as rivers. Biting stable flies have never been medically or epidemiologically documented to spread anthrax to cattle or humans, nor do they feed on dead animals—they feed on live animals. According to Hort these biting stable flies bred and spread disease in the Plague of Boils in early January. But these flies actually hibernate in winter in the pupa stage and do not mature until warm weather.6 Most problematic, if anthrax was all over the land of Egypt as Hort’s theory requires, and anthrax bacilli typically attack the blood of sheep and humans, then the Passover ritual involving widespread exposure to lamb’s blood would have spread an anthrax epidemic throughout the Israelite population—which of course did not happen.

Euglena sanguinea is green, not red, contrary to Hort. It has a tiny red so-called “eyespot,” but is overwhelmed by the 20 times greater area of green color.

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Hort’s Influence on Biblical Scholarship

Hort’s articles have had enormous influence on scholarly thinking on the Exodus, despite a disturbing and total lack of any independent scientific review in the literature. Hort’s “facts” of microbiology and geology “have not been challenged,” as the noted Exodus scholar Nahum Sarna has said,7 and it will become evident that this is due to the lack of proper scientific review that would have caught the devastating flaws. Otto Eissfeldt and Johannes Hempel, who edited the German journal of Old Testament studies that published Hort’s 1957–58 paper, stated that certain unnamed scientific authorities assured them Hort’s work was correct in its microbiology and geology. But these authorities were never identified and no substantive scientific comments were ever actually published8 so that the science could be subjected to independent review and testing.

Many commentators have unknowingly echoed this misplaced assurance that the Hort thesis was “geologically and microbiologically accurate,”9 and her “climatological, geographical, and microbiological facts” are cited uncritically in various places such as the International Standard Bible Encyclopedia and even the Encyclopœdia Britannica. Pervasive high praise of Hort runs across the spectrum of scholarship from conservative to liberal, including secular and evangelical Egyptologists, Old Testament scholars, Catholic “liberation” theologians, and Jewish seminarians.

Hort’s work has been called “excellent,” “painstaking,” “accurate,” “attractive,” “important,” “compelling,” “logical,” “sophisticated,” “thorough,” “ingenious,” “learned,” “impressive” and “significant” (Kitchen 1982; Harrison 1982:228; Elwell 1988; Hyatt 1980:339; LaSor, Hubbard and Bush 1982:138, fn. 20; Zevit 1990:42, n. 6; Lesko 2000; Hoffmeier 1992:375, 1997:149; Beegle 1972:96; de Vaux 1978:360; Childs 1974:162; Salkeld 1995; see Pfeiffer 1973:156–57; Kaiser 1998:97–99; Sarna 1986:73; 1991:38ff; Pixley 1987:42; Bush 1986:880; Encycloœdia Britannica 2000; Marr and Mallory 1996:22; Dever 2003:18). However, this first ever in-depth scientific analysis shows that Hort’s theory is riddled with numerous fundamental errors of scientific reasoning, logical flaws, misstatements of fact, and even long-exploded ancient myths about the “snow fed” sources of the Nile misreported as modern-day scientific discoveries. (Unlike Hort’s paper, the analysis here has undergone critical review by leading specialists in the fields of microbiology and Egyptology prior to publications.)

The Nile River at Thebes, with the Luxor Temple visible on the east shore.

It has not been possible to salvage the basic thesis of Hort, or her unacknowledged predecessors, by suitably modifying it, because there are so many errors across so many scientific and historical disciplines that a correction would amount to a complete reversal or negation of Hort’s theory. For example, an algae bloom would need to be at the Nile’s yearly low (not high) level, to consist of green (not red) algae that are actually toxic and not harmless, to involve the algae originating not in a distant East African plateau but in the Nile Delta, and to be generated by the water-pollution eutrophication effect of sewage runoff from the large Israelite slave population—instead of the Israelites being exempt from the alleged algae Plague, etc. (More on this in Part 2.) Thus this salvaging “correction” of Hort’s theory results in a Green Algae Plague that impacts mainly the Israelites, not the Egyptians!

Continued uncritical recital of Hort’s theory is an unfortunate result of the rush to admire the cleverness of her seemingly novel thesis and, at least for some, the misguided desire to find a naturalistic “scientific proof” of the Bible that charts a middle ground between skepticism and supernaturalism. Credit should not go to Hort anyway for the domino-effect interlinking of the Plagues from natural causes, but instead belongs to her unacknowledged predecessors, including the 1874 Lange commentary (1876, at Ex 7:25), the well-known 1902 Hastings Dictionary of the Bible (Macalister 1902:892) and the 1911 book by renowned archaeologist Flinders Petrie (35–36; see also Huntington 1926:194–209). Hort was not the first to suggest allegedly red algae and red silt combining into a Blood Plague (various 19th century Bible commentators preceded her), nor the first to suggest anthrax carried by flies (Blanc 1890). Hort’s unique contribution has been to name two particular species of algae that are nonexistent in Egypt and the Nile.

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The first plague. “He (Aaron) raised his staff in the presence of Pharoah and his officials and struck the water of the Nile, and all the water was changed to blood. The fish in the Nile died, and the river smelled so bad that the Egyptians could not drink its water. Blood was everywhere in Egypt (Ex 7:20–21)

Natural phenomena must naturally occur. Incredibly, neither Hort nor her one microbiology reference (Hort 1957:95 and fn. 19; Gessner 1955:412–13) cite any data showing that the two species of algae she has specifically implicated are actually found “naturally occurring” at Lake Tana in Ethiopia or anywhere in the Nile or East Africa. Since Hort’s supposedly red algae are green (Pringsheim 1966:1, 4–5, citing Wollenweber 1908 and Reichenow 1909; Hagen 2000; Aquasearch 2000:1–3; Graduate University 2001) and the red Nile silt is actually brown (Rzóska 1976:76, 159, 263, 269, 339, 349, also citing Petherick 1861; Talling and Rzóska 1967:640, 650; Morris, Largen, Yalden 1976:236; Entz 1976:285, 288; De Vries 1975:1349; Fairservis 1962:39), they cannot possibly have reddened the Nile.10 Egyptologist Carl De Vries of the University of Chicago Oriental Institute flatly denies Hort’s claims, stating, “the color of the Nile during flood is brown rather than red and can hardly be described as like blood in appearance” (De Vries 1975:1349). Thus the so-called “natural phenomenon” (Hort 1957:85; 1958:58) of red algae and red mud does not naturally occur (Sarna 1986:75; De Vries 1975:1349–1350; Salkeld 1995). Reports of an annual “red” Nile are mistaken according to biologists and probably motivated by a desire to evoke Biblical imagery for storytelling purposes. Additionally, aside from one text that actually substantiates mirrors the Biblical Plagues, there is a total lack of any naturally-recurring plagues in Egyptian history, even as partial occurrence (an occasional localized attack of locusts does not count as a national-scale Plague of Locusts and it is not followed or preceded by other “plagues”).11

The way Hort describes her purportedly blood-red algae one would think these species, Haematococcus pluvialis and Euglena sanguinea, are prominent in the biology of the Nile, well-known to scientists of that river, and easily found in the scientific literature on that region. In reading the actual literature one is surprised then to find her two so-called “red” species completely unmentioned. Instead, the scientific literature on the Nile is dominated every where by the names of two other unrelated species, a colorless diatom called Melosira granulata and a blue-green algae called Anabaena flos-aquae. Hort never discussed or even mentions these actual top two Nile algae, nor any of the other five principal species (four blue-greens again and another colorless diatom; Hammerton 1976:243–44). It is difficult to understand how an ostensibly scientific theory about algae in the Nile can fail to discuss or at least mention any of the actual algae in the Nile.

One would also think from Hort’s discussion that her algae are well known to be harmful. In fact, the two algae species are so harmless that one of them, H. Pluvialis, is actually sold worldwide as a human food supplement after passing human and animal tests for safety, as its strong antioxidant properties are considered anticarcinogenic and even helpful in extending athletic endurance (brands include AstaFactor, BioAstin, astaZANTHIN, Astaxin).12 The U.S. Food and Drug Administration (FDA) has had H. pluvialis-based products under study for many years and has always found them safe, with no evidence of any harmful effects found in human and animal testing or in the scientific or medical literature. The FDA issued its first ruling approving an H. pluvialis product on April 13, 1995 (FDA 1995). The other species, E. Sanguinea, may also be useable as a human food supplement, and Euglena species are in wide use as fish food.13 Neither species is toxic or considered a water pollutant or appears in catalogs of the more than 170 known algae causing Harmful Algal Blooms.14

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The scientific details of Hort’s theory will be discussed further in Parts 2 and 3, in subsequent issues of Bible and Spade.

Marr’s “Cell From Hell” Theory

Former New York City chief epidemiologist John S. Marr has proposed another red tide theory of the Plagues. But just as with Hort, there are so many scientific as well as Biblical objections to such a naturalistic theory of the Egyptian Plagues that the scheme collapses.

In Marr’s theory a different set of organisms are identified in the events of the Ten Plagues, based on his experience in the science of epidemiology, but still in a ten-month July-to-May timetable clearly based in part on Hort’s “impressive” theory, a “significant, original, and unique contribution” (Marr and Malloy 1996:9, 18, 19, 22). He attributes the Blood Plague to Pfiesteria piscicida or the infamous “cell from hell” that killed millions of fish in North Carolina in the late 1980s and 1990s. This bizarre algae-like microorganism with its 50 different life cycles includes a deadly flesh-eating piranha-like stage that leaves fish bloody messes in the water—a “Blood Plague” of sorts, with actual blood not red algae (though Marr wrongly claims the organism itself was directly “responsible for the change in the color of the Nile” to “red-colored waters”, when in fact it is basically colorless).15 Marr believes the toxic stages of the organism killed so many fish that normally feed on frogspawn that frogs then were able to proliferate in unprecedented numbers in the Nile. Thus the Plague of Frogs.

Plague number two. “So Aaron stretched out his hand over the waters of Egypt, and the frogs came up and covered the land” (Ex 8:6).

Because of the Pfiesteria toxins and the supposedly “anoxic…putrefying” waters, the frogs were forced onto land to escape, says Marr, but they quickly died because of those toxins. Without frogs to eat insects now insects had a population explosion, resulting in Plagues of Lice and Flies that brought the diseases in the next two Plagues. Livestock were then killed by a number of deadly viruses and bacteria carried by this excess number of insects, which included a type of lice (instead of Hort’s mosquitoes) plus Hort’s biting stable flies. The flies carried a bacterial disease called glanders, which “most probably” caused the Plague of Boils afflicting both animals and humans. The Plagues of Hail and Locusts occurred when they did because of bad timing, not due to a causal interlinking or domino effect, in Marr’s theory.

But Pfiesteria does not naturally occur in the Nile any more than Hort’s algae do. With its freshwater ecology the Nile evidently would be fatal even to the “cell from hell,” which is a saltwater estuary species. Marr suffers under Hort’s strange misconception that “all” red tide algae blooms “deoxygenate water” when in fact essentially the reverse is the case. Like algae generally, they oxygenate and purify water, and it is their toxins that cause problems (extremely rare hypoxic conditions require a stagnant water column and are of short duration and limited area: Palmer 1980:3–4, 21; North Carolina State University 2003; contra Marr and Malloy 1996:10a). Marr admits that glanders does not affect cattle, “cattle are resistant” he says, and biting stable flies have never been reported to carry glanders, so it could hardly have caused the Plague of Boils16 (Gilbert 1998).

Biblical scholars may have some difficultly with Marr’s proposal that the Plague of Darkness was actually a Plague of Blindness, caused, he says, by the Rift Valley Fever that supposedly produces temporary blindness (Marr’s original paper denied the involvement of Rift Valley Fever in the earlier Plagues, and endorsed Hort’s Nile dust Plague of Darkness theory).17 Actually, Rift Valley Fever causes permanent blindness and impairment of vision by damage to the retina (retinitis) about one-to-four weeks after exposure, not temporary blindness, and affects about one-to-ten percent of the cases (CDC 2002; WHO 2000; Harper 2000; Mebus 1998).

Still more difficult may be Marr’s claim that the final Plague on the Firstborn was caused by a poisonous mold growing on the tops of the grain supplies, mold which had been brought by the locusts. He thinks the firstborn were killed because they received extra portions of the food right off the top due to their privileged status and did not realize it was contaminated with fast-acting deadly mycotoxins. Objections have been raised that there would not have been any food left to contaminate after the previous Plagues. Any grain stores would have been continuously raided during the hail-and-locust induced mass famine, so that “tops” of the grain heaps would never have been left around long enough to develop mold. Why would the privileged elite eat the grain that was obviously moldy anyway, instead of the grain that was not moldy? Nor does Marr’s ingenious theory explain such things as the origin of the Passover ritual of protection from the “angel of death” by spreading lamb’s blood on doorframes (certainly widespread exposure to animal blood risks the spread of an epidemic if so many diseases were as rampant as Marr and others allege, and in this case afflicting Israelites not Egyptians, contrary to the Biblical account).18 While the spread of mold may have been accelerated by the excess moisture theorized by Hort for the early part of the series of Plagues, the food supplies with any such mold would have been consumed or destroyed in the mass famine months before the final Plague. Also, Hort’s intense drying phase that supposedly created a dust-borne Plague of Darkness would have inhibited mold formation.

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As with Hort’s theory, Marr’s theory is clever and convincing only at first glance, and does not withstand any kind of sustained scrutiny. It is well known that algae—even the strange Pfiesteria—grow in stagnant bodies of water and estuaries, not in free-flowing rivers.19 Red tides occur in slower-moving or becalmed saltwater oceans and estuaries rather than in freshwater rivers (e.g., not one of the 1,109 worldwide Harmful Algae Events in the UNESCO database occurred in a river: UNESCO 2000).

‘Red tides’ are a coastal marine phenomenon…The algae involved are species of Dinophyta [dinoflagellates] usually of the genera Gymnodinium or Gonyaulax which, having red pigments…impart a reddish tinge to the sea (Round 1981:307; see UNESCO 2000).

The eighth plague. “So Moses stretched out his staff over Egypt, and the Lord made an east wind blow across the land all that day and all that night. By morning the wind had brought the locusts; they invaded all Egypt and settled down in every area of the country in great numbers. Never before had there been such a plague of locusts, nor will there ever be again. They covered all the ground until it was black. They devoured all that was left after the hail—everything growing in the fields and the fruit on the trees. Nothing green remained on tree or plant in all the land of Egypt (Ex 10:13–15).

These environments are very unlike the massive freshwater Nile, the second largest river in the world and clearly not a stagnant pond.

Attack of the “UFO” Blister Beetles—Norton and Lyons

A novel explanation for the Ten Plagues centers on the “blister beetle” and was published in 2002 in the respected medical journal, The Lancet, but it too is based ullltimately on Hort (Norton and Lyons 2002). Subsequently, news reports out of India have claimed that certain alleged “UFO” encounters that proved injurious or fatal to humans and animals were actually caused by flying blister beetles (AP 2002).

Army dermatologist Lt. Col. Scott A. Norton at Water Reed Hospital and university medical doctor Christina Lyons invoke a sequence of events that are causally linked a feature multiple plagues of blister-inducing rove beetles (Paederus alfierii). Their scenario depends on Marr’s version of the earlier widely endorsed theory of Hort, with its crucial initiating event, the massive bloom of red algae in the Nile, and hence is likewise fatally flawed. Without a red algae plague to trigger a biological chain reaction, both theories fail. Natural phenomena must naturally occur. But as previously noted, the history of biology never records a bloom of identifiable red algae in the Nile, not even in microscopic quantities, and neither Marr’s or Hort’s algae are red.

Norton and Lyons follow the next several key steps of Hort’s disproven and impossible scenario, seemingly unaware of its scientific contradictions—the lethal rather than growth-promoting effect of the flood Nile on all such red tide algae, and the algae somehow removing (instead of adding) oxygen from the well oxygenated flood Nile, so fish die and frogs multiply. They hypothesize that the mass of frog carcasses provided carrion fodder for a “population explosion” of scavenger insects such as the blister beetle, which then caused the Plagues of Gnats and Flies (actually Beetles and Beetles). Supposedly the beetles are “focal,” which purportedly “may explain why the insects plagued the Egyptian community but spared the neighbouring Israelites.” But this is a circular argument that does not explain why the beetles had a “focal” concentration on the Egyptian locales instead of the Israelites in the first place, since both populations lived on close proximity in the “humid Nile delta.” Then Norton and Lyons say the blister beetles caused the Plague of Boils with the release of their toxin paederin, inducing painful necrotic blisters one-to-four days after exposure.

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But if the blister beetles caused the third and the sixth Plagues, and Norton and Lyons have adopted the eight-to-ten-month Hort-Marr timetable, then two Plagues and at least a month must have passed in between, not a mere one-to-four days, which is an impossibly short time interval. In addition, blister beetles cannot penetrate the tough hides of cattle or woolly sheep and goats and thus could not afflict these animals in a Plague. Large beetles are not like the “fine dust” of Exodus 9:9 in any case. Norton and Lyons have no “novel explanation” for the remaining Plagues and must de facto endorse Marr (and thus Hort) whom they mainly rely upon, and thus their theory is as equally unfounded.

Humphreys’ “Natural” Miracles

The latest naturalistic theory of the Ten Plagues comes from Cambridge materials science professor Colin J. Humphreys, who published the book The Miracles of Exodus: A Scientist’s Discovery of the Extraordinary Natural Causes of the Biblical Stories in April 2003. He uses “modern science to explain every miracle in the Exodus story” (Humphreys 2003:339). Humphreys admits that his findings on the Plagues merely “build upon, and in some cases correct, the work of Hort and also Marr and Malloy” (114). He claims that by careful scientific “detective” work paying the closest attention to “minor…details” he has proven that the Ten Plagues and other events of the Exodus were a “connected scientific sequence” of “escalating” natural events of “ever-increasing severity” that were “remarkably accurate” as recorded in the Bible (6, 9, 17, 127, 129). He has a “natural explanation” for “all of the events” of the Exodus and the only thing miraculous is the “timing” (4–5). However, Humphrey’s contribution suffers from the same fundamental scientific errors of Hort and Marr, to which he actually adds new errors and internal contradictions. Rather than proving the scientific accuracy of the smallest details of the Biblical account, Humphreys selects details that support his theory (and those of Hort and Marr) and ignores details that conflict which his theory (e.g., those showing the Bible does not depict any simplistic “escalation” in severity from one Plague to the Next—this is pure Hollywood melodrama—as the least damaging gnats plague should have been the first plague instead of the third, if the plagues were truly “escalating,” etc.).

Humphreys begins with Hort’s and Marr’s attack of nonexistent “red tide” algae and “red earth” silt in the Nile as the cause of the Blood Plague, though quibbling only over the exact algae species—which he never bothers to document as ever having “naturally” occurred in the Nile and even denies that anyone has ever investigated algae in the Nile (115–18). He is oblivious to the more than 100 years of scientific algae research in the Nile which has been cited extensively here, cataloging more than 400 species in the Nile and about 1,000 in East Africa. Humphreys boldly asserts he has “scientifically verifiable phenomenon for the first Plagues,” but contradicts himself in admitting “it is impossible now to identify the particular species of algae responsible” (118). How is it “scientifically verifiable” if the algae cannot be scientifically identified? The refutations of Hort et al. (above and Parts 2 and 3) apply with equal force to Humphreys and will not be repeated here.

Humphreys rightly recognizes that,

Although red tides in saltwater seas are relatively well known, they are unknown in flowing freshwater rivers, although they can occur in static freshwater lakes and ponds (115).

Perhaps he gained this insight from reading the present author’s summary on the ABR website (Sparks 2002) in one of his Internet searches (347). Yet he does not reconcile this correct statement of scientific fact with his own contradictory claim that such a red tide supposedly occurred in the admittedly non-static “freshwater river” Nile at the height of the annual flood—to create the Blood Plague (115, italics in original). He simply moves on to other criteria for algae bloom growth (sunlight, warm temperature, nutrients,) completely forgetting about the need for “static” bodies of water and thus how this means algae red tides are “unknown in flowing freshwater rivers.” He is oblivious to how the “large quantities” of silt suspended in the water (115–17) would block out that crucial sunlight. Humphreys claims previous investigators of the Plagues “have not fully appreciated the subtleties of the science” involved here, yet his own science is flawed with his claim that Hort’s algae “are indeed red” and his failure to grasp the “subtlety” of Hort’s argument that the algae killed the fish by oxygen starvation not by toxins. He even repeats Hort’s mythical melted “melted snow” source for the Nile (116)!

His only partial attempt to reconcile this fatal discrepancy is to declare without a shred of scientific documentation that the Nile Delta is just one huge saltwater “estuary,” and thus capable of supporting saltwater red tides (118)—an error of geology and microbiology as great as any by Hort. If, as Humphreys seems to think, the Delta as a whole (instead of just the coastal regions next to the ocean) has been overflowed with saltwater from the Mediterranean every year for thousands of years, its agricultural production would have been utterly destroyed long ago, as few crops can tolerate high salinity from such repetitive seawater incursions. The Nile washes over the Delta with freshwater not saltwater every year (in the pre-Aswan Dam days before 1970) making it the ancient “breadbasket of Egypt” and also making the Delta inhospitable to algae growth and red tides during the floods (Butzer 1976:17, 94–96, passim).

Though Humphreys mildly disagrees with Hort’s attribution of anthrax of the fifth Plague, he does buy into her anthrax theory of the Plagues of Boils, at least as one major possibility, along with Marr’s glanders disease suggestion, with disease transmission by Hort’s biting stable flies and Marr’s midges (124–27). He is unmindful of the scientific impossibilities discussed earlier—e.g., biting flies cannot bite into tough cattle hides or sheep wool and never have been shown to successfully transmit anthrax—and he again provides no scientific documentation. His seven-month timetable of the Ten Plagues (121, 144–45) is similar to Hort’s and Marr’s eight-to-ten-month chronologies, but he shifts the dates enough so that he avoids the winter cold that would put stable flies into hibernation (he has them breed in November instead of January), a fatal flaw in the Hort and Marr theories.

Humphreys adopts Hort’s theory that the first khamsin sandstorm of the year, in March, with maximum duration two-to-three days, astoundingly dried out all the exceptionally wet soil she postulates had spawned earlier plagues (frogs, flies, and locusts)—even though he also agrees with Hort’s idea that the rain with the Hail Plague added even more moisture to the ground for the locusts to breed in (133–39). Yet neither he or Hort can explain how the khamsin could have dried out all this massive water saturation of the alleged “red” silt so it would turn into dust in only the first few hours, so that a full three days of a Plague of Darkness could ensue—a Biblical “tiny detail” his detective work missed.

BSpade 16:3 (Summer 2003) p. 74

Lastly, Humphreys endorses Marr’s theory of mycotoxins in alleged moldy grain causing the Plague of the Firstborn (138–43)—again ignoring the small Biblical “detail” that there was no such food left by this time, or the logic that, since the grain was devoured continuously in the famine leading up to this time, no mold would have had a chance to grow in it, or that the Egyptian rulers would not eat the grain that was moldy. He adds a two-fold speculation that deaths of animal firstborn could be explained by a special Egyptian privileged status for firstborn animals for sacrifice, and that these would be fed first (from the moldy grain again for some inexplicable reasons). But he admits he cannot find documentation for this. “I have searched ancient Egyptian literature and can find no indication of whether or not firstborn livestock were special to the Egyptians” he writes (140).


My thanks to the following who kindly reviewed this manuscript in draft form and provided third critiques and invaluable assistance, though the final product of course is my responsibility alone: Antonio Loprieno, Chair of Egyptology, University of Basel; David Livingston, Associates for Biblical Research; Bernard Brandstater, Loma Linda University Medical Center; Donald M. Anderson, Director of U.S. National Office for Marine Biotoxins and HAB’s, Woods Hole Oceanographic Institution; Tim Wyatt, Editor, UNESCO-IOC Harmful Algae News; Ian Jenkinson, Editor, Journal of Plankton Research; the late Glenn Carnagey, Austin Seminary. My thanks to the following for their gracious assistance and/or informed comment during the past 12 years of research into the “algae plague” theories: Paul Giem, Burke Cunha, Meryl Nass, Larry Geraty, John Bloom, Gleason Archer, Lambert Dolphin, Bill Sardi, Paul Ray, Gary Byers, Rick Lanser, Doug McKittrick, Steve Williams. And my heartfelt thanks to Bryant Wood for courageously deciding to publish this work in full, sooner rather than later.


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