In the study of ancient diseases, nothing speaks like the dead.
"Bone abnormalities are a strong identification source," said Dr. Anne Grauer, anthropologist at Loyola University Chicago and president of the Paleopathology Association, during a personal interview. So it's relatively easy to date tuberculosis due to the lesions it leaves on bones. Pneumonia may be more ancient than TB, but lung tissue doesn't hold up so well after being buried.
"Another source for dating diseases is genomic data," said Dr. Charlotte Roberts, archaeologist at the University of Durham and author of the book "The Archaeology of Disease." DNA testing of samples from mummies and skeletons can conclusively identify disease. And even without the evidence of a body, genes in existing samples of TB and leprosy bacteria suggest prehistoric origin.
But the most difficult trick in defining the oldest known diseases may be in how you define the word "disease." For the purposes of this article, we'll explore only human, infectious, viral or bacterial diseases. So nix tooth decay, psoriasis, gout, obesity, rickets, epilepsy, arthritis and other human difficulties that are perhaps best classified as "conditions."
Notably absent from this list are some of history's biggest killers, including influenza, measles and the black plague. This is because these diseases require a level of population density that didn't develop until humans began living in cities. Influenza, measles and the plague are social. Malaria isn't.
We've listed 10 of the oldest known diseases, listed in no particular order. On the next page, we'll get started with a condition that thrives in close quarters.
Around 400 B.C.E., the Athenian physician Hippocrates catalogued the diseases of his world. Cholera was on the list. But while Hippocrates provides the first proof of cholera beyond a reasonable doubt, the disease likely originated along the Ganges River while Athens was still a very young place.
Cholera lives in many of the world's water sources, but it's most dangerous when it has an environment in which there are many people among whom it can spread. The Ganges River happens to be one of the most ancient locations of human population density, and so it was long, long ago that upstream users gathered in the numbers needed to pollute the water for those downstream. In other words, as more people become infected with cholera, they pollute the water supply with more bacteria, which in turn infects more people.
Interestingly, the same problem might have been a major factor in the loss of troops in Hannibal's march across the Alps. With a 50,000-soldier train, the troops and animals in front would have encountered pristine mountain streams, but those in back would have been forced to deal with putrid and potentially cholera-rich water [source: Hunt].
From 430 to 426 B.C.E., a great plague swept through the city-state of Athens. The historian Thucydides describes the symptoms this way:
What was the cause of this plague?
The Bible passage Leviticus 13:2 reads, "When a man shall have in the skin of his flesh a rising, a scab, or bright spot, and it be in the skin of his flesh like the plague of leprosy; then he shall be brought unto Aaron the priest, or unto one of his sons the priests."
But this isn't the first concrete mention of the disease. That honor goes to the Egyptian "Ebers Papyrus," written in 1550 B.C.E., which recommends, "If you examine a large tumor of Khonsu in any part of a man and it is terrible and it has made many swellings. Something has appeared in it like that in which there is air ... Then you shall say concerning it: It is a swelling of Khonsu. You should not do anything against it" [source: Nunn].
While typhoid and cholera are fairly straightforward in their aggressive spread through water sources, leprosy relies on another dispersion strategy -- that of dormancy. People can carry the bacteria that cause leprosy for 20 years or more before showing symptoms, and during this time can spread the disease.
One historical challenge in treating leprosy was diagnosis. In its early stages of expression, leprosy looks much like syphilis and somewhat like psoriasis. Misdiagnosis landed many psoriasis sufferers in leper colonies where many eventually did, ironically, contract and die from leprosy due to increased exposure.
One of the first researchers to turn a paleopathological eye on Egyptian mummies was Sir Marc Armand Ruffer, who in his 1921 book "Studies of the Palaeopathology of Egypt" described three mummies with "dome shaped vesicles" extremely similar to those expected of smallpox [source: Ruffer]. The most ancient of these mummies was dated 1580 B.C.E., and the most recent was the mummy of Ramses V, who died in 1157 B.C.E.
After his own inspection of the mummy, Donald R. Hopkins, who participated in the World Health Organization's Smallpox Eradication Program, wrote of Ramses V, "Inspection of the mummy revealed a rash of elevated 'pustules', each about 2 to 4 millimeters in diameter, that was most distinct on the lower face, neck, and shoulders, but was also visible on the arms." [source: Hopkins]
Is this conclusive? No, not necessarily, and to date there has been no modern analysis of Ramses V that could definitively determine if his condition was, in fact, smallpox. But the circumstantial evidence seems strong.
Smallpox is one of history's greatest killers, responsible for 300 to 500 million deaths in the 20th century [source: Saint Louis University].
Rabies is ingenious: Not only does it infect a host, but it also hijacks the host's brain in a way that makes the host want to bite things. This is how rabies gets a ticket to ride. And it's been doing it since at least 2300 B.C.E., when it was described in the Eshuma Code of Babylon [source: Rupprecht et al.].
The first person known to have survived rabies without a vaccination is Jeanna Giese, a Wisconsin teen who was bitten in 2004 by a rabid bat while at church. The New York Times reports that Jeanna went a month between bite and treatment, and was admitted to the hospital with symptoms of full-blown rabies [source: Rosenthal]. Doctors at the Children's Hospital of Wisconsin initiated a cocktail of coma-inducing and antiviral drugs, though Giese's family credits prayer with saving the girl's life.
The Romans offered the first cure for malaria: an amulet worn around the neck, inscribed with the powerful incantation "abracadabra" [source: Shah]. Over the years, we've attempted various other cures: adding oil to stagnant puddles to smother mosquito larvae, using pesticides, vaccines and nets, and even leveraging high-tech solutions such as a laser that shoots mosquitoes in midair. But the disease continues to infect 300 million people every year, killing 1 million of them [source: Shah].
The Wall Street Journal reports that malaria is responsible for half of all human deaths since the Stone Age [source: Shah].
Granted, that statistic extends the origin of the disease back in time past its first definite mention, which was in the Chinese "Nei Ching" ("The Canon of Medicine"), around the year 2700 B.C.E. [source: CDC].
People breathe more than 11,000 liters (3,000 gallons) of air every day [source: Nebraska Department of Environmental Quality]. And so, as you would expect, the lungs are a favorite home of bacteria, viruses, fungi and even parasites. And when anything foreign colonizes the lungs, the most common result is fluid. The umbrella term we use to describe fluid in the lungs is pneumonia.
Hippocrates wrote that fluid in the lungs should be called pneumonia if, "the fever be acute, and if there be pains on either side, or in both, and if expiration be if cough be present, and the sputa expectorated be of a blond or livid color" [source: Hippocrates]. But he also distinctly calls it a "disease of the ancients."
Where exactly does pneumonia place in this list of oldest known diseases? Because it's a soft tissue disease, the archaeological record isn't strong. But it's likely that various forms of pneumonia have been around as long as our lungs.
In 2008, a team of scientists from University College London excavated the submerged ancient city of Alit-Yam, off the coast of Israel. There, they found the buried remains of a mother and her child. Both skeletons showed bone lesions characteristic of tuberculosis [source: Lloyd]. DNA testing confirmed it: Tuberculosis is at least 9,000 years old.
Interestingly, this dig also lent evidence to an ongoing chicken-or-the-egg debate of whether we got TB from cows or they got it from us. In Alit-Yam, human skeletons showed signs of TB, while DNA from animal skeletons didn't [source: Hershkovitz et al.]. So it seems cows are not the killers we once thought.
Other historical speculation has proved equally false: Neither the fossil nor DNA records support the cause of TB as nightly revelry with fairies and the resulting lack of rest, nor is the disease the result of witches who transform the victim into a horse and then ride the victim to nightly meetings, as were once thought [source: Briggs].
While the Alit-Yam finding is the oldest confirmed case of TB, characteristic lesions have been found on bones found in Turkey, dated about 500,000 years ago [source: Lloyd].
Trachoma is a chronic infection of the upper eyelid that eventually results in the eyelid constricting and turning the eyelashes in toward the cornea. Over time, the rubbing of the constricted eyelid and especially the eyelash makes the patient go blind. This is what happened to Aetius, Paulus Aeginetus, Alexander, Trailaus, Horace and Cicero. And trachoma is described in Hippocrates and in the Egyptian Ebers papyrus [sources: Siniscal and Nunn].
But researchers make a compelling case for earlier trachoma found in a corner of the world little associated with early diseases: Australia. Aboriginal skeletons from 8000 B.C.E. show a common skull lesion around the eyes [source: Webb]. Scientists determined that these lesions were due to bone infection that had come from soft tissue infection. Though there are a few eye diseases that could fit this bill, the skeletons were found in the Australian region in which trachoma is most common today.
Mitochondria are small organelles found in nearly every cell in the human body. And they perform a function essential to human life, converting glucose from food to energy called adenosine triphosphate, or ATP, which cells can use.
But mitochondria carry their own genetic material -- separate from human DNA -- and these genes look a lot like those of bacteria. In other words, it's very likely that the mitochondria that we depend on for survival are the products of an ancient infection [source: Andersson et al.].
Whatever the infection, it predates animal life, let alone humans. So there's no use exploring the fossil record. Instead, researchers compared the genes of mitochondria to those of existing bacteria. The closest match was to bacteria of order Rickettsiales, many of which cause diseases -- including Rocky Mountain spotted fever [sources: Eremeeva and Dasch, Andersson et al.].
But remember, we're talking about a disease that existed before animal life. So the oldest disease isn't really Rocky Mountain Spotted Fever itself, but some unnamed proto-disease with genetic similarity.
Long, long ago bacteria invaded a cell. And because of this infection, we have life as we know it.
Read on to the next page for more infectious articles.
Do men's beards harbor more microbes than a dog's fur does? HowStuffWorks looks at a study that says yes.
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