6 Biblical Plagues Explained by Science

In the biblical, Christian worldview—among those who accept biblical inspiration—extraordinary recorded events may be purely natural phenomena, wholly supernatural, or a combination. That’s the question to be pondered with regard to the plagues of Egypt. Here, I shall explore the notion that six of the ten plagues of Egypt may have a plausible natural explanation or cause.

Greta Hort (1903-1967), a brilliant Danish scholar, wrote an influential article about this, called “The Plagues of Egypt.” I don’t read German, so I will rely on the descriptions of archaeologist James Hoffmeier and scientific articles dealing with similar subject matter.

1. Plague of Blood

Moses and Aaron . . . lifted up the rod and struck the water that was in the Nile, and all the water that was in the Nile turned to blood. And the fish in the Nile died; and the Nile became foul, so that the Egyptians could not drink water from the Nile; and there was blood throughout all the land of Egypt (Exod. 7:20-21).

Hort tied this “plague” to the Nile’s annual rise in July through September, where it is usually reddish in appearance owing to the presence of Roterde, particles of soil, suspended in the water. Hort posits a scenario that could result in the four conditions of red color, death of fish, foul smell, and undrinkability: millions of organisms called flagellates (Euglena sanguinea and Haematoccus pluvalius), probably originating from Ethiopia, in the floodwaters. At night, flagellates require more oxygen, which would cause the death of fish.

An article in Live Science, entitled “The Science of the 10 Plagues,” opines similarly:

The sudden appearance of red-hued waters in the Nile could have been caused by a red algae bloom, which appears when certain conditions enable a type of microscopic algae to reproduce in such great numbers that the waters they live in appear to be stained a bloody red. . . . These algae blooms can certainly be harmful to wildlife, as the algae contain a toxin that can accumulate in shellfish and poison the animals that feed on them.

Now, a suspicious reader could fairly object that these explanations deny a literal turning to blood of the Nile, which the text, prima facie, seems to assert. But it’s a question of whether the text must be taken literally, or whether it can be properly interpreted as phenomenological language, or the language of appearances. We know that the Bible often expresses that sort of language, and also that it does so specifically regarding “blood,” like in Joel 2:31 (“the sun shall be turned to darkness, and the moon to blood”) and Revelation 6:12 “the full moon became like blood”).

Joel 2:31 seems at first glance to read literally, whereas Revelation 6:12 uses the comparative and analogical term “like.” I daresay that no serious commentators would interpret either passage literally. They both clearly employ a metaphor for “red color.” Perhaps Exodus 7:20-21 is an instance of the same thing.

2. Plague of Frogs

So Aaron stretched out his hand over the waters of Egypt; and the frogs came up and covered the land of Egypt (Exod. 8:6).

Hort argued that the next five plagues were caused by the first. Frogs typically show up at the end of the Nile’s flooding in September and October. Exodus 7:25 states that “seven days passed” between the first and second plagues. The death of the frogs (Exod. 8:13) was—so Hort surmised—due to bacillus anthracis from the dying and decomposing fish. The Live Science article provides more examples of this strange phenomenon:

As it happens, the phenomenon of “raining frogs” has been reported multiple times throughout history and in a range of locations around the world. A report published July 12, 1873 in Scientific American described “a shower of frogs which darkened the air and covered the ground for a long distance,” following a recent rainstorm. . . .

And in May 2010 in Greece, thousands of frogs emerged from a lake in the northern part of the country.

3. Plague of Gnats

Then the Lord said to Moses, “Say to Aaron, ‘Stretch out your rod and strike the dust of the earth, that it may become gnats throughout all the land of Egypt’” (Exod. 8:16).

The Live Science article on the plagues makes the rather obvious point that a “pile of dead frogs” would naturally lead to “a swarm of insects of some sort.” This is perhaps the most plausible natural explanation of any of the plagues, and it would apply to the next one as well.

4. Plague of Flies

Else, if you will not let my people go, behold, I will send swarms of flies on you and your servants and your people (Exod. 8:21).

Flies are, of course, always present when dying and dead organic matter is to be found. A study from the journal Caduceus notes that fly bites might have led to the plague of boils later on.

5. Plague of Pestilence

For if you refuse to let them go and still hold them, behold, the hand of the Lord will fall with a very severe plague upon your cattle which are in the field, the horses, the asses, the camels, the herds, and the flocks (Exod. 9:2-3).

Hort maintains that this was a result of anthrax spread by the frogs of the second plague. Live Science offers a plausible theory of what may have caused this:

Rinderpest, an infectious and lethal viral disease . . . is thought to have originated in Asia, and traveled to Egypt 5,000 years ago . . . the New York Times reported in 2010. Its mortality rate was exceptionally high, often exceeding 80 percent. It killed an estimated 200 million cattle in the eighteenth century, according to a study published in the journal Medical History in 1997, and when rinderpest emerged in Africa in the nineteenth century, it killed 5.2 million cattle, causing one third of the population of Ethiopia to die of starvation, a study published in the journal Science reported in 2008.

6. Plague of Boils

And it shall become fine dust over all the land of Egypt, and become boils breaking out in sores on man and beast throughout all the land of Egypt (Exod. 9:9).

Based on Deuteronomy 28:35 (knees, legs, foot), Hort deduced that this was caused by a fly from the fourth plague: Stomoxys calcitrans, which carried anthrax. The infection would have been spread as a result of these flies coming in contact with rotting animals after the fifth plague. Stomoxys calcitrans, also known as the stable fly, is indeed able to transmit disease, including boils. A scholarly article devoted to this topic states,

Anthrax . . . affects animals and humans, inducing pulmonary, gastro-intestinal, or cutaneous symptoms, including a boil-like skin lesion. . . . Outbreaks are most common in areas characterized by alkaline, calcareous soil, and in warm environments with periodic episodes of flooding. . . .

B. anthracis infections can also be mechanically transmitted by stable flies.

Another similar article noted that “most of the soils in Egypt are alkaline, with pH values from 7 to 9.”

Of course, there are four more plagues to explore: hail and thunderstorms, locusts, darkness, and the taking of the Egyptian firstborn. Can we find natural explanations—albeit not purely natural explanations—for these as well? The answer is yes . . . with one exception.