Philippa Kaur

Leprosy can be caused by two species of bacteria, Mycobacterium leprae or Mycobacterium lepromatosisnobeastsofierce Science/Alamy
A form of leprosy affected people in the Americas long before the arrival of Europeans, contrary to popular belief.
“The narrative around leprosy has been always been that it’s this awful disease that Europeans brought to America,” says Nicolàs Rascovan at the Pasteur Institute in Paris. “Well, our discovery changes that.”
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The vast majority of leprosy cases worldwide are caused by the bacterium Mycobacterium leprae. But in 2008, Xiang-Yang Han at the University of Texas MD Anderson Cancer Center and his colleagues discovered a second causative agent, M. lepromatosis, in two people from Mexico who had leprosy. Since then, scientists have found more cases of this pathogen in the US, Canada, Brazil and Cuba – as well as in four people in Singapore and Myanmar.
Wanting to know more about this understudied pathogen, Rascovan teamed up with Han and other researchers, as well as Indigenous communities, to analyse ancient DNA from 389 people who lived in the Americas before European contact.
They found M. lepromatosis in the remains of one person near the Alaska-Canada border and two others along the south-eastern coast of Argentina, all carbon-dated to about 1000 years ago. The bacteria’s genomes varied slightly, hinting at distinct strains separated by around 12,000 kilometres. “It spread so fast, on a continental level, in just a matter of centuries,” says Rascovan.
DNA from dozens of modern cases – mostly from the US and Mexico – revealed that nearly all contemporary strains are essentially clones, showing only minor changes since ancient times. But the team also identified one rare and unusually ancient strain in a modern person that hadn’t turned up in archaeological remains, suggesting that at least two distinct lineages of M. lepromatosis are still infecting people in North America today – alongside the M. leprae strains introduced by Europeans.
Combined, the analyses suggest that the bacteria have been branching out and evolving in the Americas for nearly 10,000 years. About 3000 years ago, one line of the pathogen mutated into a form that now infects red squirrels in the UK and Ireland – leading to problems like swollen skin and crusty lesions.
As for its origins, genetic data show that M. lepromatosis and M. leprae split from a common ancestor more than 700,000 years ago, although where in the world that divergence happened remains unknown.
Modern cases of M. lepromatosis seem to affect the blood vessels, especially in the legs and feet – unlike M. leprae, which mainly attacks the nerves, says Han. In some people carrying M. lepromatosis, the blood flow gets blocked, causing the skin to die and break down. That can lead to deadly complications, including severe secondary infections by bacteria like Staphylococcus aureus. This disease can also spread beyond the skin, turning up in organs like the liver and spleen. Consequently, some people die before their bones have time to show any signs of leprosy.

That could help explain why archaeologists hadn’t identified leprosy in ancient remains from the Americas, says Han. While skeletons in Europe and Asia often show classic signs of bone damage from leprosy, the ancient individual from Canada in this study had only vague jaw lesions that could be caused by many conditions – and the two skeletons from Argentina showed no signs of leprosy at all.
Annemieke Geluk at Leiden University in The Netherlands says this “beautiful study” has forced a rethinking of the disease’s history. “My teaching slides state that there was no leprosy in the Americas before Europeans colonised it,” she says. “Now I have to update my slides!”
Beyond that historical significance, the research also sheds lights on a pressing public health issue. Leprosy is re-emerging in parts of the world, she says, and rising antimicrobial resistance could make it harder to treat. “Surveillance is very important,” says Geluk. “We need a global effort to map what strains are out there.”

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Archaeologists excavate part of the medieval wall system in MongoliaTal Rogovski
Long before the Great Wall of China was constructed, other monumental walls were built across the Eurasian steppes – but they weren’t designed to defend against Mongol armies. Recent excavations reveal that they were erected to control movement of people or demonstrate power, much like border walls today.
The Great Wall of China spans many thousands of kilometres, the longest stretch running some 8850 kilometres. This part dates from the Ming dynasty (AD 1368 to 1644) and served as a physical barrier to defend against Mongol raids.
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Unlike the Great Wall, which is – as the name implies – made up of large walls, the earlier system is a network of trenches, walls and enclosures stretching approximately 4000 kilometres across more northerly regions in China, Mongolia and Russia.
It was built between the 10th and 12th centuries by several dynasties, chiefly the Jin dynasty (AD 1115 to 1234), which was founded by Jurchen people from Siberia and north-east China, who were mainly pastoralists.
Gideon Shelach-Lavi at the Hebrew University of Jerusalem and his colleagues had already surveyed and mapped the walls using satellite imagery and drones, but now they have studied a section running for 405 kilometres through what is now Mongolia and excavated at one of the enclosures.
The structures were made up of a ditch about 1 metre deep and 3 metres wide, with the earth from it piled up on one side, creating a wall of compressed earth that may have been a metre or two tall. Then, every few kilometres along the wall, there was a thick, square, stone enclosure, about 30 metres across.
What the walls were built for hasn’t been clear. There is very little historical documentation about them and they weren’t built at natural geographic borders, says Shelach-Lavi.
Many historians thought they were built to stop the armies of Genghis Khan, who ruled the Mongol Empire from 1206 until 1227, says Shelach-Lavi.
The structures wouldn’t have been particularly effective defensively, though. “This was not meant to stop invading armies,” says Shelach-Lavi.
Instead, he suggests it was more of a show of power – to demonstrate that the area was under the control of the Jin dynasty. The wall would also have funnelled people through gates at the enclosures, so the flow of people, goods and animals could be managed. It might also have been used to prevent small raids, even if not stopping armies, he says.
“The idea, I think, is to channel those people to where you have those enclosures, so you can control them, you can tax them,” he says. “It’s a matter of controlling who is moving, and in this respect, it’s not very different from what we see today.”

Finds at the enclosure also shed light on how the people there may have lived. “This is a pastoralist area,” says Shelach-Lavi. “We find a lot of evidence in the region of people living off herding and hunting and fishing.”
And yet, at the enclosure, the researchers found coins from the Han Chinese Song dynasty, which was at war with the Jin dynasty, as well as ceramics, a plough head and a stone platform or bench that could be heated and used as a stove or bed.
This implies that significant resources were invested into the garrison’s construction and maintenance, says Shelach-Lavi, and also that the people lived here all year round and practised agriculture. “That’s surprising because even today, they don’t do agriculture in this place,” he says.

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Brains preserved for hundreds of years can contain intact proteinsAlexandra Morton-Hayward
It is now possible to obtain proteins from preserved soft tissues like brains. The new method could reveal details of human history and prehistory, and of evolutionary history, that were previously impossible to know. That includes what animals ate, the microbes they had in their guts and even how human brain cells changed over evolutionary time.
“There are soft tissues preserved over half a billion years of Earth history,” says Alexandra Morton-Hayward at the University of Oxford. Such tissues could now be mined for proteins. “The amount… More

The shore of the river Thames in London, close to where the woman’s remains were foundCrispin Hughes/Alamy
A woman was tortured for days, killed and then put on display at the side of the river Thames in central London around 1200 years ago. The case is thought to be one of the only examples of a judicial execution of a woman in medieval England in the archaeological record.
“This isn’t the story of one blow, and it’s not clandestine,” says Madeleine Mant at the University of Toronto in Canada. “It’s the story of purposeful violence, and… More

A projectile point, made from the bone of a grey whale, from the Duruthy rock shelter in Landes, FranceAlexandre Lefebvre
Hunter-gatherers living along the shores of the Bay of Biscay crafted hunting tools from the bones of at least five different whale species 20,000 years ago, marking the oldest evidence of manufacturing objects from whale remains.
Although there is evidence of Neanderthals gathering and eating molluscs in what is now southern Spain around 150,000 years ago, current findings suggest that ancient humans didn’t regularly use coastal resources for food and raw materials until around 19,000 years ago… More

One of a child’s most important jobs is to make sense of the worldCavan Images/Alamy
Hello, Cruel World!Melinda Wenner Moyer (Headline Home (UK); G.P. Putnam’s Sons (US))
The unfortunate thing about parenting books is that, in my experience, once you become a parent you are too time-poor and exhausted to read them. As a result, my bedside table is stacked with parenting manuals of which I’ve read the first five pages a dozen times before passing out.
If this sounds like you, the latest book by science journalist Melinda Wenner Moyer should be top of your pile. … More

Ħaġar Qim, a megalithic temple complex in southern MaltaFelix Choo / Alamy Stock Photo
Several 5000-year-old temples in Malta seem to have been oriented towards specific stars, suggesting the temples could have been schools for celestial navigation.
Ancient people constructed seven temples across the Maltese archipelago from 3800 to 2300 BC. Fashioned from large, cut stones weighing several tonnes, the complexes are among the earliest megalithic structures ever built.

“Most researchers agree that the temples display features associated with ritual behaviour,” says Huw Groucutt at the… More

Children can display empathy before they are old enough to talkMStudioImages/Getty Images
Children between 9 and 18 months old already demonstrate empathy, suggesting this ability starts at an earlier age than previously thought, even for babies from different cultural backgrounds.

“If I don’t understand your emotions, I can’t communicate with you and I can’t respond to your emotions, so it’s an essential skill – but we only know how it develops in a small part of the world,” says Carlo Vreden at the Leibniz… More