Cave of Denis, bounty of archaeological discovery
The first issue of the journal Nature was published on November 4, 1869, costing fourpence. It has since been the standard bearer of scientific research, reflected in such iconic papers as "A structure for deoxyribose nucleic acid", published in 1953 — a paper that led to Crick and Watson's Nobel Prize for identifying the structure of DNA.
This past week has seen another notable article published, in Nature Communications, that describes the discovery of a new human species that was only possible because of the surviving ancient DNA in a tiny human finger bone.
The scene is Denisova cave in the remote Altai Mountains of Siberia. In the cave, once occupied by a monk called Denis, the cultural deposits go down metres in depth and thousands of years in time. Painstaking excavations by Russian archaeologists have traced the prehistoric occupation of the cave through the stone tools and fragments of bone — fragments because most had been crunched by hyaenas. The project was joined by international scientists, including my son Tom and his wife Katerina, both specialists in dating.
In 2008, a tiny finger bone found its way to the Max Plank Institute, in Leipzig, for DNA analysis and it turned the evolution of the human past on its head, for it came from a unknown species that the excavation team named Denisovan. This has led to a hunt for more Denisovan bones, made the more significant by the fact that modern people from Tibet to New Guinea count Denisovans among their ancestors.
There is a new analytical technique that can identify a bone fragment by extracting its collagen, and Tom and Katerina took bags of bone chips back to Oxford from Denisova Cave. After analysing more than 1000, their graduate student Samantha Brown struck gold: a fragment of human bone.
Off to Leipzig it went, followed by a long and anxious wait for the DNA results to come through. The stunning result was a world first: the bone came from a young girl whose mother was a Neanderthal, and father a Denisovan, who lived about 90,000 years ago. Not only was this unique discovery the world's first known human hybrid, but it featured on the front cover of Nature. Since then, the search for more Denisovans has reached the highlands of Tibet and tropical Laos and the seas off Taiwan. It seems Denisovans and Neanderthals once had a common ancestor about 390,000 years ago and placing both in the jigsaw of human evolution is continuing apace.
For the full story, read Tom Highams' The World Before Us: How Science is Revealing a New Story of Our Human Origins.
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RNZ News
07-08-2025
- RNZ News
Scientists say it may be possible to protect ageing brains from Alzheimer's with an old remedy — lithium
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In a series of experiments reported Wednesday in the journal Nature, researchers at Harvard and Rush universities found that depleting lithium in the diet of normal mice caused their brains to develop inflammation and changes associated with accelerated ageing. In mice that were specially bred to develop the same kinds of brain changes as humans with Alzheimer's disease, a low-lithium diet revved the buildup of sticky proteins that form plaques and tangles in the brains that are hallmarks of the disease. It also sped up memory loss. Maintaining normal lithium levels in mice as they aged, however, protected them from brain changes associated with Alzheimer's. If further research supports the findings, it could open the door to new treatments and diagnostic tests for Alzheimer's, which affects an estimated 6.7 million older adults in the United States, according to the US Centres for Disease Control and Prevention. The research provides a unifying theory that helps explain so many of the puzzle pieces scientists have been trying to fit together for decades. "It is a potential candidate for a common mechanism leading to the multisystem degeneration of the brain that precedes dementia," said Dr. Bruce Yankner, a professor of genetics at Harvard Medical School, who led the study. "It will take a lot more science to determine whether this is a common pathway ... or one of several pathways," to Alzheimer's, he added. "The data are very intriguing." In an editorial published in Nature, Dr. Ashley Bush, a neuroscientist who directs the Melbourne Dementia Research Centre at the University of Melbourne in Australia, said the researchers "present compelling evidence that lithium does in fact have a physiological role and that normal ageing might impair the regulation of lithium levels in the brain." He was not involved in the study. Close examination of human and animal brain tissues, along with genetic investigations in the study, found the mechanism that appears to be at play: Beta amyloid plaques - the sticky deposits that gum up the brains of Alzheimer's patients - bind to lithium and hold it, including the type that's normally present in the body, as well as the commonly prescribed form. This binding depletes lithium available for nearby cells, including important scavengers known as microglia. When the brain is healthy and functioning normally, microglia are waste managers, clearing away beta amyloid before it can accumulate and can cause harm. In the team's experiments, microglia from the brains of lithium-deficient mice showed a reduced ability to sweep away and break down beta amyloid. Yankner believes this creates a downward spiral. The accumulation of beta amyloid soaks up more and more lithium, further crippling the brain's ability to clear it away. He and his colleagues tested different lithium compounds and found one - lithium orotate - that doesn't bind to amyloid beta. When they gave lithium orotate to mice with signs of Alzheimer's in their brains, these changes reversed: Beta amyloid plaques and tangles of tau that were choking the memory centres of the brain were reduced. Mice treated with lithium were once again able to navigate mazes and learn to identify new objects, whereas those who got placebos showed no change in their memory and thinking deficits. In its natural form, lithium is an element, a soft, silvery-white metal that readily combines with other elements to form compounds and salts. It's naturally present in the environment, including in food and water. Scientists have never fully known how it works to improve mood - only that it does. The original formula for 7Up soda included lithium - it was called 7Up Lithiated Lemon Soda - and touted as a hangover cure and mood lifter "for hospital or home use." 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Neither he nor any of his co-authors have a financial interest in the outcome of the research, he said. The National Institutes of Health was the major funder of the study, along with grants from private foundations. "NIH support was absolutely critical for this work," Yankner said. The new research corroborates earlier studies hinting that lithium might be important for Alzheimer's. A large Danish study published in 2017 found people with higher levels of lithium in their drinking water were less likely to be diagnosed with dementia compared with those whose tap water contained naturally lower lithium levels. Another large study published in 2022 from the United Kingdom found that people prescribed lithium were about half as likely has those in a control group to be diagnosed with Alzheimer's, suggesting a protective effect of the drug. But lithium's use in psychiatry caused it to become type cast as therapeutic, Yankner said. 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Consistently finding lower lithium levels in the brains of people with memory loss amounted to a smoking gun, Yankner said. "At first, frankly, we were sceptical of the result because it wasn't expected," said Yankner. But it held up even when they checked samples from other brain banks at Massachusetts General Hospital, Duke and Washington universities. "We wanted to know whether this drop in lithium was biologically meaningful, so we devised an experimental protocol where we could take lithium selectively out of the diet of mice and see what happens," Yankner said. When they fed the mice a low-lithium diet, simply dropping their natural levels by 50 percent, their brains rapidly developed features of Alzheimer's. "The neurons started to degenerate. The immune cells in the brain went wild in terms of increased inflammation and worse maintenance function of the neurons around them, and it looked more like an advanced Alzheimer patient," Yankner said. 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"You know, oftentimes one finds in science that things may have an effect, and you think you know exactly why, but then subsequently turn out to be completely wrong about why," he said. -CNN
1News
07-08-2025
- 1News
New mRNA vaccines saved millions — so why is the US pulling funding?
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Otago Daily Times
01-08-2025
- Otago Daily Times
Four-day work week benefits
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