Secrets of a whale graveyard
Scientists have uncloaked the mystery of an ancient fossilized graveyard of dozens of whales lying side by side with bizarre, walrus-faced dolphins and swimming sloths. The fossils, unearthed about three years ago in Chile’s Atacama Desert, probably record a series of mass strandings about 6 million to 9 million years ago that were caused by blooms of algae fed by the iron-rich sediments of the Andes Mountains, according to a study published online in the journal Proceedings of the Royal Society B.
The international team of researchers believes about four waves of carcasses washed into what once was a placid tidal basin within a period of weeks, then were buried in sediments that accumulated over 10,000 to 16,000 years, said the study’s lead author, Nicholas D. Pyenson, curator of fossil marine mammals at the Smithsonian Institution.
How the fossils came to rest 130 feet above sea level is less a mystery than it may seem: The Nazca, Antarctic and South American plates have been grinding against each other for millions of years, pushing up the Andes Mountains. The whale skeletons, all from the rorqual superfamily that includes modern blue whales, were largely intact, with few signs of scavenging other than the marks of crab claws, Pyenson said. “South America did not have polar bears or any large terrestrial carnivores that would scavenge and disarticulate the skeletons,” he said. “Crabs must have had a field day out there.”
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‘microbial Pompeii’ is found on teeth
Scientists have discovered the DNA of millions of tiny organisms entombed in the ancient dental plaque of four medieval skeletons. The findings, published in the journal Nature Genetics, have implications for research into what our ancestors ate, how they interacted, and what diseases they fought, the authors write. Lead author Christina Warinner, a molecular anthropologist at the University of Oklahoma, said, “This is a game changer.”
Matthew Collins of the University of York, a co-author on the paper, put it this way: “What we found is a microbial Pompeii.”
Calcified plaque is the bumpy stuff you might notice coating your teeth. The layers of calcified plaque entomb the bacteria that also live in our mouths — turning them into small fossils even when we are alive. And when we die, these dense, calcified micro-fossils remain intact, even as most of the rest of us decomposes. “When you get DNA from bones it is so damaged and there is so little of it left,” Warinner said. “When we analyzed the dental calculus we got 100 to 1,000 times more DNA fragments than we would have from a bone.”
From those DNA fragments, the team determined that the bacteria associated with human periodontal disease have not changed much in 1,000 years even as hygiene and diet have. They also found that ancient oral bacteria had a gene that could allow it to resist low-level antibiotics, just as some of our oral bacteria have today.