For most of us, leprosy—better known as Hansen’s Disease—is a horrific illness that belongs in the Middle Ages. But it’s much older than that. It’s also one of the reasons why nobody should take Jesus or Christianity seriously. Today, let me show you some of the newest research about this disease, and how once again Greta’s Law holds true: We do, indeed, consistently replace supernatural explanations of our world for natural ones, but we have never done the reverse.
(This post and its audio ‘cast first went live on Patreon on 8/19/2025. They’re both available now! Author’s Note: In this post, I refer to Hansen’s Disease by its older name, “leprosy.” Out of respect for those affected by it, I do not use the term “leper,” though some quotes use it. From introduction: The evolution of armadillos.)
SITUATION REPORT: Leprosy is way, way older than we thought
Last month, researchers got a surprise about leprosy. They obtained two samples of Mycobacterium lepromatosis from 4,000-year-old Chilean human remains. The samples were “highly intact,” which isn’t normal for their age.
M. lepromatosis is one of two leprosy-causing bacteria. The other is M. leprae, and it’s been found in numerous remains up to 5000 years old. According to the NIH, it might even be 40,000 years old. It’s the strain responsible most cases of leprosy. Scientists only identified its kissing cousin, M. lepromatosis, in 2008. But this lesser-known variant is way more destructive, between the two.
The surprise came when scientists examined these two samples’ genomes. These days, they can do some sophisticated math involving timelines using a genome’s mutation rate. By doing that, they found that the two leprosy strains split 26,800 years ago. (And here’s a possible surprise: Leprosy is related to tuberculosis, which we talked about recently. Scientists think the diseases split 36 million years ago.) American lineages of the strain split around 12,600 years ago, which is around the time when humans began moving into South America.
Previously, scientists thought leprosy came to the Americas through European colonists. But that seems unlikely now. Now it seems like leprosy hopped a ride in the bodies of the earliest settlers of the Americas. We’re rewriting the earliest history of one of mankind’s most baffling diseases. Today, I’ll show you its history—and how we discarded earlier ideas about it for much, much better ones.
And armadillos are involved. What’s not to like about this story?
The how and what of leprosy
M. lepromatosis generally lives in Mexico and the Caribbean. But researchers have found it in—of all things—red squirrels in Ireland and the UK, which means it likely hopped a ride there from the Americas. Its more common variant, M. leprae, once lived all over Europe and Asia, but now it’s found chiefly in countries without robust medical infrastructure for all citizens, like India and Brazil.
Red squirrels carry this more common variant too, along with nonhuman primates. So far, we only know for sure that nine-banded armadillos can pass it to humans, probably through handling or consumption of their meat. (Yes, I WTAF’d too. Turns out these germs might like their lower 32°C body temperature. At least pink fairy armadillos are safe, so far.) In part because of the nine-banded armadillo, 100-200 cases of leprosy pop up in the United States every year, mostly in the South where these critters live. However, doctors diagnose about 200k new cases a year worldwide, mostly in India and Brazil.
Leprosy isn’t super-contagious. It doesn’t transmit through casual contact or even sharing food. Most people need months of prolonged exposure to sufferers. Once this parasite finds a host, it possibly won’t even show signs of its presence for years.
Nor is it instantly fatal. In and of itself, it doesn’t even really kill its host. Instead, it deforms and disfigures. Sufferers can live with leprosy for decades if they’re careful.
And they must be, if they want to live.
The bacteria attacks peripheral nerves that control sensation and muscle movement. Sufferers lose their sense of touch. If the disease affects their hands and feet, sufferers might not be able to feel pain or injuries. They might not notice infections in those injuries, either. That’s what causes most of the worst damage: their wounds don’t heal. As their bodies reabsorb the cartilage in their faces and digits, their fingers and toes shorten and their noses collapse.
If the sufferer can get to a decent doctor, they can recover. We developed the first effective treatments for leprosy in 1941. These days, modern medicine can cure it in months if it’s caught early. It’s no longer an ancient terror.
How most ancient people responded to leprosy…
Many ancient cultures used the same words to describe most skin diseases, so it’s hard to say if any of these writers meant leprosy in their work. But researchers do have some good guesses here. They think physicians in India likely identified the disease around 2000BCE, and were working on treatments by 600BCE.
Chinese physicians might have been on the case by 500BCE. The Greeks might have begun catching the disease around the 5th century BCE, spreading it from India to Egypt, and Herodotus wrote about it in his histories around 440BCE. Some of them called it “elephantiasis” because sufferers often developed rough, scaly skin.
Around 150CE, the physician Aretaeus of Cappadocia wrote about leprosy in very accurate terms, even nailing its transmission via respiration.
But none of this sounds supernatural. Physicians described it, and they tried real-world measures to treat it. No, it’s the Near Middle East that really turned a scary-looking disease into a divine curse, and Christianity that settled much of the stigma on it.
…And how Ancient Jews responded to it…
Between the Old and New Testaments, evangelical site Got Questions claims the Bible mentions leprosy “upwards of 40 times, depending on the Bible version.” They describe this disease as “a powerful object lesson of the debilitating influence of sin in a person’s life.”
That said, we don’t know for sure exactly what skin condition Old Testament writers meant in chapters like Leviticus 13. The word they used for these conditions, tzara’ath, did include leprosy, though. Either way, someone who had “scaly outbreaks” or spots or swellings became “unclean.” That person had to be isolated. After a generous isolation period, if the skin condition persisted then that poor sorry bastard had to make a lot of personal changes very quickly:
A diseased person must wear torn clothes and let his hair hang loose, and he must cover his mouth and cry out, ‘Unclean, unclean!’ As long as he has the infection, he remains unclean. He must live alone in a place outside the camp. [Leviticus 13:45-46, Berean Standard Bible translation]
We see similar purity-obsessed treatment elsewhere in the Old Testament, too.
Sidebar: Old Testament stories that probably involve leprosy
In 2 Kings 5, we also see the story of Naaman, a great Aramean military commander who contracted leprosy. At the advice of his wife’s Jewish slave, he visited Elisha, a Jewish prophet. Elisha told Naaman to bathe seven times in the Jordan River to cure his condition. When Naaman did that, his leprosy was cured.
Yahweh also curses Miriam, Moses’ sister, in Numbers 12. Miriam got pissy about Moses taking a foreign wife, so Yahweh cursed her with leprosy for seven days. For that week, she had to follow the Levitical rules—isolating herself outside the camp and everything.
So these skin conditions (along with other ailments) were viewed as divine curses. Ancient Judeans handled them in ways that were meant to purify the body as much as keeping infected people away from the healthy. Impure people couldn’t participate in their community, but they were also cut off from their god (<– that’s quite an interesting paper, btw).
Centuries later, conquering Romans considered Judea a backwater hellhole. They regarded its inhabitants as unruly, ignorant, and violent. But they viewed the area itself as strategically important, so they needed control of it. Though they gave Judeans a great deal of autonomy and religious freedom, these conquerors had their limits. Their occasional arrogance and strict enforcement of those limits brought about a great deal of tension between Judeans and Romans, which culminated in a war that the Judeans decidedly lost.
Amid this turbulence, leprosy still lurked and struck victims down—seemingly at the will of Yahweh.
…And how early Christians responded to it
The earliest-written of the Gospels, the Book of Mark, includes references to what were likely leprosy sufferers in its very first chapter (however, keep in mind that the words describing leprosy might refer to other serious skin conditions). It might be the first fully-described healing miracle attributed to Jesus:
Then a leper came to Jesus, begging on his knees: “If You are willing, You can make me clean.”
Moved with compassion, Jesus reached out His hand and touched the man. “I am willing,” He said. “Be clean!” And immediately the leprosy left him, and the man was cleansed. [Mark 1:40-41]
We find references to similar miracles scattered across the Gospels, some even sounding like they were cribbed from Mark 1:
- Matthew 8:1-4
- Matthew 10:8
- Matthew 11:5
- Luke 5:12-15
- Luke 17:11-19 (this one involves ten sufferers!)
At all times, the Gospel writers refer to leprosy as something that Jesus could cure through his divine magic.
As leprosy advanced through Europe, early Christians developed a complicated view of leprosy. They simultaneously regarded it as a divine punishment and curse, but at the same time perhaps also as a way for sinful people to participate in Christ’s Passion and gain forgiveness for not only their own sins, but those of others. Pope Gregory the Great (d. 604CE) thought that in a metaphorical way, Jesus himself “appeared in the aspect of a leper.” So serving and comforting leprosy sufferers could be a social good that any good Christian could feel comfortable doing.
At the same time, it’s not hard to find medieval doodles of leprosy sufferers (local archive) begging for alms and ringing bells to warn others of their presence. These sufferers were unable to earn a living or engage freely with others. They utterly depended on the grace of others to survive. Rulers passed laws restricting sufferers’ movement, with many confined to the 19,000 leprosy hospitals and colonies in Europe by the 1300s.
Then, for reasons we still don’t fully understand, leprosy began dying out in the 1400s. By the 1600s, it had gone from a regular feature of life to nearly nonexistent in Europe. Some scientists think immunity quickly developed in Europeans, while others wonder if the Black Death or tuberculosis competed too efficiently for potential hosts.
A few centuries later, we developed effective treatments for it. And that was that, for Europe and most of the Americas at least.
Greta’s Law strikes again
When I read this story, it really struck me hard to realize that once again, a supernatural explanation got discarded for a purely natural one. Gospel writers cast Jesus as a healer who could even lift the curse of leprosy. But it was scientists who identified it and developed real cures for it, not any gods or angels. They discovered that no gods or demons caused it, nor any need for redemptive suffering. It was just a purely natural disease with purely natural behaviors that we can understand in purely reality-based ways.
In 2008, Greta Christina pointed out this exact truth on her blog:
Not even the apparent god of the entire universe understood what leprosy was a millennium ago, but plain old humans figured it out. And not only did we figure it out, but we learned how to cure it. Humanity went from Yahweh’s curses to cute armadillos carrying diseases that modern medicine can cure in months!
We no longer need to console leprosy sufferers with their proximity to Jesus through their anguish. We don’t require anyone to perform purification rituals to be rid of it. Sufferers don’t need to know how exactly their treatments work for them to work.
In the Gospels, the character of Jesus didn’t see fit to tell anyone exactly what was going on with leprosy. He found it important enough to heal, but not important enough to stop—or even explain. Nor did he warn his followers not to see leprosy sufferers as spiritually or morally deficient in any way. Instead, he perpetuated his cultural myths in responding to this disease.
And in turn, as we have done with thousands of other supernatural explanations, we discarded this one and replaced it with a natural, earthly one that tells people exactly what’s happening and how to deal with it.
Just imagine what supernatural explanation will land on the Reality chopping-block next!
NEXT UP: The arrogance of a recent so-called “revival” reveals evangelicals’ utter lack of perspective. See you soon! <3
Please support my work!
Thanks for reading, and thanks for being part of our community! Here are some ways you can support my work:
0 Comments