It’s pretty standard for scientists to look at human skeletons to reconstruct past human health. But a new approach looks not at our ancestors themselves but the hardened gunk on their teeth to re-create the timeline of human dietary changes.
Scientists performed that analysis by looking at an array of ancient teeth. They found that shifts in the human diet over the millennia have led to big drop-offs in the diversity of good bacteria in our mouths—and the result is a severely weakened oral ecosystem and an increased risk of various diseases.
Saliva contains bacteria and minerals which accumulate on our teeth as plaque. Since skeletons can’t brush their teeth, this film eventually crystallizes on tooth enamel to become almost bone-like, preserving the bacterial DNA inside it. The DNA of bacteria in crystallized plaque provides a snapshot of a person’s diet, health and oral pathogens.
This Stone Age human jawbone contains a tooth with the
oldest filling ever found
We’re lucky to live in a modern age, an age when, instead of ripping out a painful cavity-ridden tooth, we can have dentists drill away the rotten bit and plug up the hole with a filling. But a new discovery reveals that fillings aren’t just modern conveniences: they date back to the Stone Age. Researchers have discovered that a tooth on a 6500-year-old human jawbone has a large cavity covered by a beeswax cap—making that wax the oldest dental filling ever discovered.
Archaeologists working near Leipzig, Germany, have unearthed a surprisingly arrangement of more than 100 dog’s teeth in a grave between 4,200 and 4,500 years old. The way the teeth are arrayed suggests that they might have been sewn as decoration onto a piece of leather or textile which has since decayed, prompting the team who found it to call in the remnants of a purse. Taking a closer look has revealed that the teeth come from dozens of different dogs.
The team has already found hundreds of graves at the site, as well as artifacts like an amber necklace, bone buttons, stone tools, and, in one later grave, a pound of gold jewelry. Unfortunately, they have just a few years left to learn what they can from the place: it’s due to become a coal mine in 2015.
Photograph courtesy Klaus Bentele, LDA Halle
Tartar on the teeth of a young male Australopithecus sediba
To someone in the dentist’s chair, plaque is an unwelcome discovery, but to paleoanthropologists, it’s a gold mine of information. And the hardened plaque, called tartar or calculus, on the teeth of two Australopithecus sediba individuals revealed that these early humans had a taste for trees that included not only fruit, but also bark, wood, and leaves.
What’s the News: The bacterial hordes that call your mouth home—and yes, even if you brush rigorously, you’ve got ’em—are generally a pretty benign bunch. Mostly they just mooch around, snagging tastes of whatever you’re eating, but Streptococcus mutans, the bad boy that causes cavities, releases tooth-corroding acid whenever you eat sugar. Even mouthwash that kills everything it touches can’t save you from the ravages of S. mutans in the long term; it just grows back, along with the rest of your bacteria.
Scientists who study the mouth microbiome, however, think that a mouthwash that kills S. mutans and leaves the rest of the bacteria to take over S. mutans‘s real estate could spell the end of cavities. In a small clinical study last year, one team found that one application of the mouthwash knocked down S. mutans levels, and that harmless bacteria grew back in its place. If the mouthwash pans out, it could join the ranks of an emerging new type of treatment: better living through hacking the microbiome.
What’s the News: Parents going broke to pay for their offspring’s braces and orthodontistry can finally blame somebody besides their mildly malformed children: our farmer ancestors. A study published this week in the Proceedings of the National Academy of Sciences found that people living in subsistence farming communities around the world have shorter, wider jaws than those in hunting and gathering societies. This leaves less room for teeth, which have changed little in size or abundance over human history—and may help explain why crooked choppers and a need for orthodontia are so common, study author Noreen von Cramon-Taubadel tells the BBC. “I have had four of my pre-molars pulled and that is the only reason that my teeth fit in my mouth,” she says.
From across the pond comes a ravishing collection of scientific imagery. The Wellcome Collection, a London museum, has just announced the winners of its Wellcome Image Awards.
The 21 award winners, selected from images acquired by the Wellcome Collection over the last 18 months, were chosen both for their ability to enhance scientific understanding and for their aesthetic appeal. Many use colour to better illustrate hard-to-see features. [New Scientist]
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Did Neanderthals enjoy some diversity in their diet? A study out in this week’s Proceedings of the National Academy of Sciences claims to offer more evidence that these hominids ate a wide-ranging diet including cooked grains and grasses rather than the cartoon caveman’s diet of meat, meat, and more meat.
Amanda Henry has made the case before; in April 2008 she said that micro-fossils of plant material could be found in the plaque of recovered Neanderthal teeth. Now, she says, her team has found more traces of grains and plants stuck in the teeth of Neanderthal fossils unearthed in Belgium and Iraq.
After analyzing a selection of these particles from European and Middle Eastern Neandertal dental remains, the team found “direct evidence for Neanderthal consumption of a variety of plant foods.” … Some of the Paleolithic snacks seem to have included legumes, date palms and grass seeds. The grasses were from the Triticeae group, which includes wild varieties of barley, rye and wheat relatives. [Scientific American]
Furthermore, the grains and starches present show the signature of having been cooked—probably by boiling in water—according to study author Dolores Piperno. To test this out the researchers themselves cooked similar grains, and the effects matched what they saw in the Neanderthal samples.
The movie was called Jaws for a reason. The great white shark’s powerful chompers make it a feared marine killing machine. However, researchers have found, it takes a while to grow into that ferociousness—adolescent great whites don’t yet have strong enough jaws to complete an attack on tougher prey without harming themselves, and it takes until adulthood for that jaw strength to develop.
The study by Toni Ferrara and colleagues, forthcoming in the Journal of Biomechanics, used the scanning technique called computerised tomography (CT) to take a look at the great white’s developing jaw, and compare it to a relative: the sand tiger shark (also called the grey nurse shark).
With these scans, they were able to create digital three-dimensional models of the sharks’ heads. The models revealed that the great white’s jaws are reinforced by layers of tough “mineralised cartilage”, which take years form. So until the sharks grow to approximately 3m [10 feet] long, they are unable to gouge chunks out of larger, tougher prey, such as sea mammals. [BBC News]
Neanderthals, it would appear, grew up in a big hurry. In a new study in the Proceedings of the National Academy of Sciences this week, Harvard anthropologists who studied Neanderthal teeth samples say that the evidence captured in those teeth show the rate at which they developed. Compared with human children, Neanderthal kids raced though their developing years and into adulthood, the researchers say.
Tanya Smith and colleagues used advanced X-ray scans of the tooth fossils of Neanderthals and the humans who lived concurrently with them to discover the layers therein. She says such scans reveal “growth lines” that serve the same purpose as tree rings–they allow researchers to measure the individual’s development year by year, and to determine his or her exact age at death.
Even when compared to some of the earliest human teeth, taken from remains of humans who left Africa 90,000 to 100,00 years ago, the differences were clear. Human teeth grew more slowly, pointing to more leisurely periods of youth. “This indicates that the elongation of childhood has been a relatively recent development,” the study said. [AFP]