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A surprising history of malaria is revealed by clues from ancient bones

In modern times, malaria is thought of as a tropical disease but evidence from ancient bones reveals a different narrative. Above: In Ambowuha, Ethiopia, Birtukan Demissie and her siblings are protected from mosquitoes that carry the disease with a bed net. Joining them is the family cat.
Louise Gubb
/
Corbis Historical via Getty Images
In modern times, malaria is thought of as a tropical disease but evidence from ancient bones reveals a different narrative. Above: In Ambowuha, Ethiopia, Birtukan Demissie and her siblings are protected from mosquitoes that carry the disease with a bed net. Joining them is the family cat.

How old is malaria?

Researchers used to think it was two or three thousand years old at most — a modern disease that appeared long after most humans gave up the nomadic hunting lifestyle and formed towns and cities, making it easier for diseases to spread quickly and efficiently.

But a study published Wednesday in Nature paints a different picture — and may change the way scientists and historians view this ancient pathogen.

Malaria is at least 5,500 years old, the study found and might even be much older, the researchers say.

“We still haven't really figured out where and when it exactly originated,” Johannes Krause, an author of the study and director at the Max Planck Institute for Evolutionary Anthropology, told NPR. “It actually seems that we have to go quite further back in time, maybe 10,000 years.”

Clues from very old bones

For this study, researchers gathered slivers of ancient human bones from archaeologists, museums and their own excavations around the world.

Then they examined the tiny samples carefully and, for the first time ever, found even tinier traces of malaria parasites preserved on them.

That alone was a “big surprise,” Krause said. It’s hard enough to find human DNA in a bone sample that’s thousands of years old, “but what's the chance to find the pathogen that was present in the person when he died?”

Next, the scientists compared the DNA of those older parasites to modern-day versions of malaria and discovered a few more surprises.

The two forms of malaria found in the Americas were both brought by Europeans, the researchers determined.

Plasmodium vivax, a type of chronic malaria, was introduced when Europeans colonized South and North America beginning in the 15th century.

And Plasmodium falciparum — a type of deadly malaria that is “one of the most problematic human pathogens known today,” Krause said — was spread by the slave trade. Slavers and enslaved peoples likely got sick with malaria before their journeys or on the ships, and then mosquitoes in the Americas could pick up the pathogen by biting the infected person, then pass it on to their next victim. (Malaria is spread by mosquito bites, not from person to person.)

That put to rest the theory that malaria was already present in the Americas when Europeans colonized and enslaved other people.

Another surprise: scientists used to think P. vivax was older than P. falciparum – but so far, there’s no evidence of that.

What else they hope to figure out

The relatively new field of archaeogenetics – the study of ancient DNA – has previously examined the history of bubonic plague.

Archaeogeneticists like Krause will continue tracing malaria’s path as far back in time as possible to understand where it emerged and how it evolved.

This study shows how the history of malaria is really a story of human movement – and the ways we shape our environment, including pathogens, experts said.

The researchers were surprised to find malaria in the bones of someone from the Iron Age in Austria – and in bones from Tibet, high in the Himalayas, where malaria-carrying mosquitoes can’t survive. They believe the person contracted the illness elsewhere and then traveled to Tibet — an insight into human mobility using pathogen DNA that’s never been done before, Krause said. And it shows how widespread malaria has been throughout the centuries.

These results were “exciting,” Nathaniel Comfort, a professor of the history of medicine at Johns Hopkins University who was not affiliated with this study, told NPR. “It would suggest that movement, rather than stasis, is the underlying driving force in the spread of malaria.” That means malaria wasn’t spread by the creation of towns and cities, where once-nomadic humans stayed put – it was spread as humans migrated and forced the migration of other people through the slave trade.

By challenging long-held beliefs about the origins and spread of malaria, “it's the kind of scientific result that can change the way we narrate the history,” he said, and “it could transform our understanding of these ancient diseases.”

That understanding could also help us better understand infectious diseases today.

“It can help dissolve some racial stereotypes having to do with medical conditions,” Comfort said, referring to the mistaken idea that people of color in the tropics are more susceptible to diseases like malaria. “It's a reminder that we create a lot of the situations in which diseases flourish, and those are correlated with race and class, and now the poorest and most powerless people tend to have the disease concentrated in that area because of human actions, not because they're naturally more susceptible to disease.”

The study also offers a new insight into malaria’s identity. Today it’s seen as a tropical disease. “As this paper really clearly shows, it's far from that,” he said. “It seems to have spread worldwide, even to the Himalayas – that's astonishing.” The reason that malaria has become a disease of the tropics, he said, is because some countries were able to put considerable resources into wiping it out in their part of the world.

A scary geography lesson

Meanwhile, the history of malaria is still being written. It sickens millions and kills about 608,000 people per year. “It's a huge health burden,” said Krause.

After several decades of progress battling the dangerous parasite, in more recent years cases have gone back up — particularly due to climate change, as the environmental range where malarial mosquitoes can survive expands.

“In parts of the world where it has been already extinguished in the past, now it's actually coming back because of the tropics expanding” as the globe warms, Krause said. For instance, a Maryland man got sick from malaria in 2023 and he had no known history of travel.

“It's something that was actually quite present in the past, in a lot of places that today you wouldn't think about being home to malaria. But that's also kind of the scary bit in some ways, because if it was there 200 years ago, there is also a chance for it to come back.”

Melody Schreiber is a journalist and the editor of What We Didn't Expect: Personal Stories About Premature Birth.

Copyright 2024 NPR

Melody Schreiber
[Copyright 2024 NPR]
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