Tag Archives: teeth

Artificial enamel is even stronger than real teeth

Credit: Pixabay.

Enamel, the hard mineralized surface of teeth, is the hardest thing in the human body. Pound for pound, enamel is tougher and harder than steel. Its unique mix of minerals, water, and organic material makes it tough enough not to dent while at the same time making it durable enough to withstand decades of grinding and tear – but only for so long. Depending on your diet and how well you take care of your teeth, you can stave off tooth decay but you can only postpone the inevitable for so long. The problem is that once teeth lose their enamel, it never comes back, and tooth decay is right around the corner.

Despite many attempts to replicate the wondrous properties of enamel, most efforts have proven in vain. A new study, however, has reignited hopes that such a thing is actually possible after researchers at the University of Michigan have devised a way to make artificial enamel. It goes without saying that this would be a huge leap for dentistry, which still uses decades-old filling technology to repair cavities.

Mimicking enamel in the lab is incredibly challenging due to its complex structure of interwoven hydroxyapatite nanocrystals, which are one-thousandth the thickness of human hair. These crystals are arranged in wires, which become coated in magnesium by enamel-producing cells, and then are woven together into a very strong mesh, which is further organized into twists and bunches.

Researchers have struggled while attempting to reconstruct the complex and multi-layered organization of enamel. But where others failed, the authors of the new study finally succeeded. They encased wires of hydroxyapatite in a malleable metal-based coating, resulting in a structure that has a soft layer that can absorb the powerful shock of a bite but is strong enough to take a lot of pressure without denting.

In fact, the artificial enamel is stronger than the natural variation due to swapping the magnesium-rich coating with the much stronger (and non-toxic) zirconium oxide. To test the material’s strength and elasticity, the researchers cut a piece with a diamond-bladed saw then used a mechanical press to apply pressure steadily until it started to crack. The artificial enamel surpassed natural enamel in six different measures, including hardness, elasticity, and shock absorption.

Now, the artificial enamel doesn’t mimic natural enamel to the tee. It lacks the complex 3D woven patterns of natural enamel, but its parallel wire structure is the closest scientists have come to true enamel thus far.

The research could drastically improve the construction of artificial teeth, as well as significantly reduce tooth decay through new and improved fillings that last much longer. However, the best dental treatment is still prevention, which is why doctors recommend having a good dental routine and opting for teeth straightening as early as possible. Comparing options currently available on the market shows there is a good number of quality aligners and braces manufacturers to choose from.

But beyond dentistry, the hard artificial enamel could prove highly useful when incorporated into implantable electrons and biosensors, such as pacemakers and blood pressure monitors.

“This method of making artificial enamel lends itself to commercial production and it can be produced for the manufacture of artificial teeth,” Nicholas A. Kotov, of the University of Michigan, told i.

It’s still early to make any predictions when this product might reach the market, but since all the components of the material are biocompatible, researchers hope to soon begin trials on both animals and humans. The artificial enamel hasn’t been binded to natural enamel yet, a crucial step in tooth repair, so this will be one of the many tests the material needs to pass before we can finally enter a new age of dentistry.

The findings appeared in the journal Science.

Fossil Friday: the story of how tusks evolved from teeth

What, exactly, makes a tusk a tusk? And how did they come to be? New research by U.S. paleontologists sheds light on both of these questions.

Left side of the skull of a dicynodont Dolichuranus fossil used in the study. The tusk is visible at the lower left. Image credits: Ken Angielczyk.

Multiple animal species today have tusks. From elephants to walruses, however, one thing they all have in common is that they’re mammals. This wasn’t always the case, new research reveals. The history of tusks, according to a team of paleontologists at Harvard University, the Field Museum, the University of Washington, and Idaho State University started with an ancient relative of mammals that lived before the age of the dinosaurs.

Those relatives were dicynodont (meaning “two canine teeth), a species that shared some of the characteristics of mammals but also reptiles — including sporting a turtle-like beak.

Tooth or tusk?

“For this paper, we had to define a tusk, because it’s a surprisingly ambiguous term,” said lead author Megan Whitney, a postdoctoral researcher at Harvard University and a UW doctoral alum, in a press release. “Enamel-coated teeth are a different evolutionary strategy than dentine-coated tusks. It’s a trade-off.”

For this study, the team defined tusks as being teeth not covered in enamel (i.e. they’re entirely made of dentine), that extend out past an animal’s mouth, and keep growing throughout the individual’s lifetime. Using this definition, the authors set out to determine the evolutionary history of such appendages. They worked with thin slices cut out from the teeth of several fossil species in order to determine when tusks first appeared. They investigated these using micro-CT scans, to determine how the teeth were attached to the skulls of the animals, and to check for signs of continuous growth around their roots.

Dicynodonts lived from 270 to 201 million years ago, roughly, so they’re quite ancient animals. As a group, they were very diverse, ranging in size from a rat to a modern elephant. They got their name from the two distinctive teeth in their upper jaws, teeth which were the focus of this study.

According to the findings, some dicynodont teeth were indeed tusks. One important finding is that there wasn’t a clear-cut transition between the two. The team analyzed 19 different dicynodont specimens comprising 10 species, finding that tusks evolved independently several times in this extinct clade. Another important hint that we’re looking at the first evolution of tusks was that the earlier dicynodont species only showed teeth, whereas tusks started making an appearance among the later species to arise in this clade.

The enamel layer on this Diictodon caniform (the colorful ring on the cross-section) makes it resemble teeth more than tusks. Image credits Megan Whitney.

“We were able to show that the first tusks belonged to animals that came before modern mammals, called dicynodonts,” said co-author Ken Angielczyk, a curator at the Field Museum in Chicago. “Despite being extremely weird animals, there are some things about dicynodonts — like the evolution of tusks — that inform us about the mammals around us today.”

The authors further report on some adaptations dicynodonts had to go through to enable the evolution of true tusks. These include flexible ligaments connecting the tusks to their jaws, and a reduced overall rate of tooth replacement. The roots of their tusks were hollow, as well, to allow for fresh dentine to be continuously added over time.

Apart from the findings of this study, the team’s classification of what exactly constitutes a tusk and how they’re different from regular teeth is more broadly applicable to other species. In particular, it gives us insight into the different tasks these structures are meant to serve.

The enamel layer on the surface of our teeth is harder than dentine, making it more resilient to wear and tear. But it’s also much harder to heal damaged enamel than it is to heal dentine. Its presence also prevents teeth from growing continuously, as tusks do. Animals with tusks use them for fighting or rooting through the ground, so they’re much more exposed to damage than teeth. A complete enamel covering would be impractical in this situation, as it would present a liability. Since tusks regrow, damaging or losing a tusk isn’t a death sentence. If they had the same structure as teeth, however, they couldn’t be replaced, and any damage would constitute a direct and significant threat to an individual’s survival.

An example of a true tusk in the dicynodont Lystrosaurus, with a hollow pulp cavity in its root where fresh dentine would have been created. Image credits Megan Whitney.

“Tusks have evolved a number of times, which makes you wonder how — and why? We now have good data on the anatomical changes that needed to happen for dicynodonts to evolve tusks,” said co-author Christian Sidor, a UW professor of biology and a curator at the UW’s Burke Museum of Natural History & Culture. “For other groups, like warthogs or walruses, the jury is still out.”

Most of the dicynodont fossils analyzed in this study were unearthed in Tanzania and Zambia. They’re currently stored in a range of museums in the U.S., and are scheduled to be returned to the National Museum of Tanzania and the Livingstone Museum in Zambia after the conclusion of the research project.

The study “The evolution of the synapsid tusk: insights from dicynodont therapsid tusk histology” has been published in the journal Proceedings of the Royal Society B.

Frogs lost their teeth more than 20 times in their evolutionary history

Of more than 7,000 species of frogs currently leaping across the world, there’s only one that we know of that has teeth on both upper and lower jaws. But that doesn’t mean it’s always been like this. In fact, it seems like the frog lineage has had quite a contradictory history, having grown and lost their teeth over 20 times during their evolution, far more than any other vertebrate group. The main reason why virtually all frogs have settled on a toothless mouth is due to their specialized diet consisting of small insects, researchers reported in a new study published this week.

The green frog, Rana clamitans, has teeth on its upper jaw and is a common species in the Eastern U.S., including Florida. Credit: Florida Museum / Daniel Paluh.

Who needs teeth anyway when you got a super slick tongue

Teeth can confer a competitive advantage to the animals that have them, allowing them to access different sources of prey that wouldn’t have been available otherwise. Scientists believe they first appeared more than 400 million years ago in fish, such as the armored fish Romundina stellina, which is an even more ancient creature than sharks. In time, teeth were acquired by sharks, most bony fish, and ultimately the first vertebrates that roamed onto land.

Although teeth may seem like simple tissue, looks can be deceiving. They form through a complex process and can therefore be taxing from an energy standpoint. This is why some species lost their teeth, such as birds who discarded their teeth around 100 million years ago with the advent of the beak, and so did whales and frogs. The latter’s relationship with teeth, however, has always been challenging to investigate the fragile nature of most frog skeletons.

“If you open a frog’s mouth, chances are you will not see teeth even if they have them, because they’re usually less than a millimeter long,” or smaller than the tip of a pencil, said Daniel Paluh, a Ph.D. candidate in the University of Florida’s department of biology and lead-author of the new study.

In the 19th century, famed paleontologist Edward Cope classified all toothless frogs into the same group, which he named Bufoniformia, suggesting that frogs grew and subsequently lost their teeth once. But later analyses involving modern genetic techniques showed that frogs lost their teeth more than once over the course of their evolution in independent cases.

It was only recently that Paluh and colleagues delved deep into this conundrum. Where others had failed, the team of researchers succeeded thanks to Florida Museum’s massive compilation of CT scans for over 20,000 vertebrate specimens. This allowed the researchers to study the jaws of countless frog species in great detail without any concern that they might damage valuable museum samples.

This enlarged, contrast-enhanced CT scan of a toothless Guinea snout-burrowing frog, Hemisus guineensis, shows muscles (pink), skeleton (tan), glands (yellow), cardiovascular system (red) and central nervous system (purple).  Credit: Florida Museum / Edward Stanley.

In order to paint a broad picture of dental changes in frogs, the researchers included representatives of all amphibian groups, analyzing patterns of tooth loss through time. To complement the CT scans, they employed a previously published map of evolutionary relationships between amphibians based on genetic data.

The results were striking. They showed that, counter to the debunked Bufoniformia hypothesis, frogs have undergone “rampant tooth loss.” Teeth seem to appear and disappear constantly through time in groups as distantly related as toads and poison dart frogs. It happened at least 20 times, according to the researchers, more times than all other vertebrate groups combined.

The driving force of this evolutionary pressure seems to be diet. Specifically, a diet of tiny insects was strongly correlated with a lack of teeth.

“Having those teeth on the jaw to capture and hold on to prey becomes less important because they’re eating really small invertebrates that they can just bring into their mouth with their highly modified tongue,” said Paluh. “That seems to relax the selective pressures that are maintaining teeth.”

That’s not surprising at all. After all, specialized mammals that feed on ants and termites, such as pangolins and anteaters, also lack teeth. Instead, they rely on their extra-long tongues to gather prey.

But that’s not to say frogs don’t have teeth at all. When frogs do have teeth, they only have them on their upper jaw, which they use to assist in capturing prey. For the most part, however, frogs will use their projectile tongues to catch prey. What’s more, neither frogs nor amphibians really chew their prey. In the rare instances when a frog actually uses its teeth, it’s usually just to grab and hold on to their food.

Although the sheer number of times frogs have grown and lost teeth is staggering, the show isn’t over yet. According to the researchers, many open questions remain — and not just about frogs. The huge library of CT scans, part of a project known as oVert, allows anyone with an Internet connection to access 3D models derived from the scans, which depict distinct features of organisms, including bones, vasculature, internal organs, muscle tissue. In the future, scientists at the Florida Museum plan on leveraging this database even further to make new discoveries.

“We now have lots of new questions in my lab inspired by the surprising things turning up from 3D imaging from the oVert project, and those will lead us both back into museum collections and to the field to see what these animals are doing in the wild,”  said David Blackburn, Florida Museum curator of herpetology and Paluh’s thesis adviser.

The findings were reported in the journal eLife.

Ancient teeth confirm: people have been trading internationally for thousands of years

We often hear how we’re living in a more interconnected world than ever before — and that is true. But people have never lived in complete isolation from others. New research comes to support this view, by showing that long-distance trade in food and spices was already taking place between Asia and the Mediterranean region over 3000 years ago.

Image credits John Oliver.

Spices such as turmeric and foods including bananas were known and present in the Mediterranean region during the Bronze Age, the paper explains, much earlier than previously assumed. The authors further note that such plants were not endemic to the Mediterranean, so the only way they could get there was via long-distance trade.

Megiddo Mall

“Exotic spices, fruits, and oils from Asia had reached the Mediterranean several centuries, in some cases even millennia, earlier than had been previously thought,” says Philipp Stockhammer from LMU, who led the research. “This is the earliest direct evidence to date of turmeric, banana, and soy outside of South and East Asia.”

The international team of researchers analyzed the tartar (dental deposits) on the teeth of 16 people unearthed in excavations at the Megiddo and Tel Erani sites in modern-day Israel. This area mediated any ancient travel and trade between the Mediterranean, Asia, and Egypt. If you wanted to travel between these places in the 2nd millennium BCE, you had to go through the Levant.

What the researchers were looking for was food residue, such as proteins or plant microfossils, that remained preserved in the dental plaque over the last thousands of years. From there, they hoped, they could reconstruct the local diet.

Dental plaque or calculus is produced by bacteria that live in our mouth. As it forms it can capture small particles of food, which become preserved.

“This enables us to find traces of what a person ate,” says Stockhammer. “Anyone who does not practice good dental hygiene will still be telling us archaeologists what they have been eating thousands of years from now!”

The techniques they used fall under the domain of paleoprotemics, a relatively new field of science concerned with the study of ancient proteins. The team managed to identify both “ancient proteins and plant residues” from the teeth, revealing that their owners had consumed foods brought from faraway lands.

It was quite surprising for the team as well. Such techniques are difficult to use, they explain, because you have to piece together what food people ate judging solely from the proteins they contained. The proteins themselves must also survive for thousands of years until analyzed, so there’s also quite a lot of luck required to pull it off.

The team confirmed the presence of sesame in local diets at the time (sesame is not an endemic plant to the Levant), suggesting that it had become a staple food here by the 2nd millennium BCE. The teeth of one individual from Megiddo showed turmeric and soy proteins, while one individual from Tel Erani showed traces of banana proteins — all of them likely entering the area through South Asia.

“Our analyses thus provide crucial information on the spread of the banana around the world. No archaeological or written evidence had previously suggested such an early spread into the Mediterranean region,” says Stockhammer. “I find it spectacular that food was exchanged over long distances at such an early point in history.”

Naturally, the team can’t rule out that this individual traveled or lived in South Asia for a period of time, consuming local foodstuffs during this time. They also can’t estimate the scale of any trades going on, only find evidence that such networks probably existed.

Still, the findings showcase how early long-distance trade began, and they go to show that people have been living in and building an interconnected world for a very long time now. While definitely interesting and important from an academic point of view, such results also help to put our current social dialogues around globalization, trade, and immigration into perspective.

The paper “Exotic foods reveal contact between South Asia and the Near East during the second millennium BCE” has been published in the journal PNAS.

Fossil Friday: ancient shark bones turn out to be the teeth of a new species of flying dinosaur

Researchers at the University of Portsmouth have made a lucky discovery in the collections of the Sedgwick Museum of Cambridge and the Booth Museum at Brighton: a new species of pterosaur.

The fossils as seen from different angles. Scale bar represents 10 mm. Image credits Author links open overlay Roy E. Smith et al., (2020), Proceedings of the Geologists’ Association.

The fossils have been part of these collections for almost 100 years now, being first uncovered between 1851 and 1900. They were found at the height of phosphate mining activity in the English Fens area. As was regularly the practice among workmen there at the time, they quietly sold any fossils they found to collectors for some extra money.

Before we judge them too harshly, it pays to keep in mind that they had a direct hand to play in the discovery of a new species, even if unwittingly. Since their discovery, the fossils were assumed to have belonged to a species of shark. However, the work of University of Portsmouth Ph.D. student Roy Smith revealed that, in fact, they belonged to a new species of pterosaur.

Sharkosaur

Smith was examining (what we believed to be) the shark fin spines found in the fens when he noticed that they weren’t spines at all. They definitely looked the part, at least superficially, but there were also some details that didn’t fit the bill. Unfortunately, they were just teeth (connected to a bit of beak), so we don’t have enough material to describe the species it belonged to.

“One such feature are tiny little holes where nerves come to the surface and are used for sensitive feeding by the pterosaurs. Shark fin spines do not have these, but the early paleontologists clearly missed these features,” he explains. “Two of the specimens discovered can be identified as a pterosaur called Ornithostoma, but one additional specimen is clearly distinct and represents a new species. It is a palaeontological mystery.”

“Unfortunately, this specimen is too fragmentary to be the basis for naming the new species. Sadly, it is doubtful if any more remains of this pterosaur will be discovered, as there are no longer any exposures of the rock from which the fossils came. But I’m hopeful that other museum collections may contain more examples, and as soon as the Covid restrictions are lifted I will continue my search.”

Smith’s supervisor, Professor Dave Martill, explains that the material we do have “simply differs from Ornithostoma [a pterodactyl lineage] in subtle ways”, similarly to how “a great white egret might differ from a heron”. He adds that it’s unlikely that the animal had a significantly different body structure to other pterodactyls, but that it likely diverged most in areas such as “color, call, and behavior than in the skeleton”. Still, he describes the findings as “tantalizing”.

“Pterosaurs with these types of beaks are better known at the time period from North Africa, so it would be reasonable to assume a likeness to the North African Alanqa”, he adds. “This is extremely exciting to have discovered this mystery pterosaur right here in the UK.”

Part of the significance of the work is finding hints of a new species, the two researchers say. But they’re also valuable in showcasing how re-examining dusty museum collections for old material we assume was already identified can help us make whole new discoveries.

The paper “Edentulous pterosaurs from the Cambridge Greensand (Cretaceous) of eastern England with a review of Ornithostoma Seeley, 1871” has been published in the Proceedings of the Geologists’ Association.

Neanderthal milk teeth show their babies were raised and weaned similar to us

A model of Neanderthals at the Vienna Natural History Museum. Credit: Wolfgang Sauber.

Here’s another thing where humans and Neanderthals seem to have the same: child-rearing. According to a new study conducted by an international team of researchers, Neanderthals started to wean their infants at around 6 months of age, which is also when modern humans start introducing solid food in the diets of their children.

Ancient milk teeth and Neanderthal parenting

It seems like with each new study on Neanderthals, the conceptual gaps between our close extinct relatives and Homo sapiens seem increasingly narrower. For instance, Neanderthal artifacts like eagle talon necklaces found in Spain were very similar to jewelry made by humans. Their burial practices also suggest that Neanderthals employed many cultural practices mirroring those of humans.

Now, thanks to geochemical and histological analyses of three Neanderthal milk teeth, scientists have gained new insights into Neanderthal parenting.

“How different Neanderthals are to us is a topic currently under intense debate. These ‘cousins’ of ours are important for understanding our evolution but also our future. Being able to understand Neanderthals’ natural history is one of the most stimulating intellectual challenges,” Federico Lugli and Stefano Benazzi, co-authors of the study from the University of Bologna in Italy, told ZME Science.

Credit: Federico Lugli.

The teeth belonged to three different Neanderthal infants who lived between 70,000 and 45,000 years ago in northeastern Italy, a region that has always been rich in food and natural shelters like caves, making it a Neanderthal hotspot for at least 45,000 years.

Like tree rings, growth lines on teeth are deposited on a year by year and reflect the diet of the children. Using laser-mass spectrometry, the researchers measured strontium concentrations in the dental samples, which showed Neanderthals started introducing solid food in their children’s diets at around 5-6 months of age.

“Studies on Neanderthals’ early infancy are few, and they mainly deal with morphology and not with behavior. Our research sheds light on the understanding of how Neanderthal children grew up and how they were fed. Our study highlights a weaning pattern very similar to Homo sapiens and demonstrates once again how much Neanderthals are so similar and yet so different from us,” the researchers told ZME Science.

Across all human cultures, children are weaned at around 6 months of age. Around this time, mother’s milk alone is not enough to supply an infant’s calorie requirements for the growing human brain.

Neanderthal’s metabolic constraints and early development have always been a matter of contention among scholars. The new findings tip the balance of the debate towards more similarities with humans, suggesting that Neanderthal newborns probably had a similar weight to modern human babies. Neanderthal mothers may have also had a similar gestational history and development to human mothers. Previously, a study by researchers at Griffith University in Brisbane, Australia, found that Neanderthal children were fully weaned after the age of two.

“We have already started working on other archaeological contexts to broaden our knowledge of a hidden part of the fossil record, which is the little-known world of Neanderthal children and their mothers. Still, we will apply our methodologies on other fossil and even contemporary humans, actively searching for discrepancies or similarities in parental care and mother-child relationship,” the Italian researchers said.

The findings appeared in the Proceedings of the National Academy of Sciences.

How whitening strips can damage your teeth

Dentists all over the United States are having a hard time keeping up with the demand for brighter, white teeth. And because these services can be expensive, many turn to whitening strips that they can apply themselves at home. However, Americans’ obsession with perfect white teeth might sometimes backfire if these strips aren’t used accordingly.

According to a study performed by researchers at Stockton University in Galloway, NJ, whitening strips can damage the protein-rich dentin tissue found beneath the tooth’s protective enamel.

Teeth are made up of three distinct layers. The innermost layer is a connective tissue that helps keep the teeth safely in place; the middle layer is made of dentin, the yellowish tissue that makes up the bulk of all teeth; and the external layer is made of enamel, which determines the brightness of teeth.

Teeth-whitening strips are made of a flexible plastic that is coated in a thin layer of whitening gel. The main active ingredient is hydrogen peroxide, an oxidizing agent that is also the main substance found in products that bleach hair.

Overusing hydrogen peroxide as a color-lightening agent is known to damage the hair and the scalp. And, according to researchers led by Kelly Keenan, Associate Professor of Chemistry at Stockton, hydrogen peroxide can have a similar effect on teeth, potentially attacking the dentin layer of teeth.

The Stockton professor and her students reported that perhydroxyl radicals produced by peroxide break up long-chain organic molecules into smaller molecules.

Whitening strips are applied to the teeth such that the gel penetrates the tooth and starts the whitening process. Even the best teeth whitening kits have to be applied each day for two to three weeks.

The researchers followed these instructions in the lab using human teeth extracted from cadavers. In order to model the human mouth environment, the teeth were soaked in artificial saliva and washed.

Then, the research team measured the level of collagen and other proteins that make up dentin and compared the results to unbleached teeth, as well as a different set of teeth that underwent whitening three times.

The results suggest that hydrogen peroxide can pierce the enamel layer and infiltrate dentin, which is made of 90-95% collagen. In the case of teeth that were whitened three or more times, the collagen seemed close to disappearing.

“We sought to further characterize what the hydrogen peroxide was doing to collagen,” said Keenan. “We used entire teeth for the studies and focused on the impact hydrogen peroxide has on the proteins.”

In another experiment, the researchers treated pure collagen with hydrogen peroxide and then analyzed the protein using a gel electrophoresis laboratory technique that allows the protein to be visualized.

“Our results showed that treatment with hydrogen peroxide concentrations similar to those found in whitening strips is enough to make the original collagen protein disappear, which is presumably due to the formation of many smaller fragments,” said Keenan.

Does this mean that using whitening strips can damage your teeth? The research suggests that this may be a risk when using such products, although more research is required as the study itself has some important limitations. For instance, it didn’t consider the fact that collagen can be regenerated. Also, the effect of the strips wasn’t studied in a real human mouth, which might prove to be very important.

But, as the teeth whitening industry is set to grow to $7.4 billion by 2024, cosmetic dentists are becoming increasingly concerned as to what this may mean for patients.

If you’d like to have whiter, brighter teeth without having to risk your oral health, dental experts recommend avoiding foods that are known to cause staining such as coffee, tea, red wine, and soda. If you consume these foods, rinse your mouth with water right after drinking or eating in order to reduce the staining effect.

Neanderthal cave painting

Neanderthal teeth could chomp on hard plants like nuts and seeds

Although research suggests that Neanderthals ate mostly meat, our extinct cousins had a formidable jaw structure that should have enabled them to process a variety of foods. Now, a new study has significant evidence pointing to the fact that Neanderthals, as well as other early hominins, likely consumed nutritious hard plans like seeds and nuts without suffering structural damage to their teeth.

Credit: Wikimedia Commons.

In order to tell what kind of foods our early ancestors could have consumed safely, researchers at Washington University in St. Louis first ran a test involving primate teeth in the lab. The aim of this experiment was to see what kind of impact various foods might have on the teeth’s enamel microscopic structures.

“We found that hard plant tissues such as the shells of nuts and seeds barely influence microwear textures on teeth,” Adam van Casteren, lecturer in biological anthropology at Washington University in St. Louis, said in a press release. “If teeth don’t demonstrate elaborate pits and scars, this doesn’t necessarily rule out the consumption of hard food items.”

During one such test, a seed shell attached to a probe was dragged across the enamel from an orangutan tooth. This motion replicated the kind of forces exerted by chewing. Four different types of food particles were attached to the probe. And, in the end, neither produced significant dental microwear, such as scratches, fractures, or pits, the authors reported in the journal Scientific Reports.

Previously, researchers had performed mechanical tests on primate teeth, but this was the first time that actual hard food particles were used to measure any damage they might have caused.

Combined with previous assessments of Neanderthals’ sturdy jaws, the new findings suggest that our close human relatives and other early hominins would have been more than equipped to chew large amounts of nuts and seeds without threatening the structural integrity of their molars.

“When consuming many very small hard seeds, large bite forces are likely to be required to mill all the grains,” van Casteren said. “In the light of our new findings, it is plausible that small, hard objects like grass seeds or sedge nutlets were a dietary resource for early hominins.”

This all makes sense since early hominin craniodental morphologies evolved before the advent of cooking or sophisticated food processing. In other words, back in the day, most food at our early ancestors could hunt or forage was pretty tough to chew. Individuals who could chew on hard plants without losing their teeth would have been favored by natural selection.

This information is useful for anthropologists who are left with only fossils to try to reconstruct ancient diets.

“Our approach is not to look for correlations between the types of microscopic marks on teeth and foods being eaten — but instead to understand the underlying mechanics of how these scars on tooth surface are formed,” van Casteren said. “If we can fathom these fundamental concepts, we can generate more accurate pictures of what fossil hominins were eating.”

Last week, a different study concluded that Neanderthals dived under the ocean for shells that they fashioned into tools. The shells were modified to be used as scrapers and were more efficient than thin flinty rocks, which can’t sustain a sharp edge. It’s possible that they also used their hard teeth and jaws to manipulate the shells in the tool manufacturing process.

Near east neolithic people fashioned jewelry out of human teeth

At a 9,000-year-old archaeological site, researchers unearthed a most peculiar find: human teeth drilled through the root. By all accounts, the ancient teeth must have been employed to fashion a necklace or some other kind of jewelry.

Credit: Journal of Archaeological Science.

Archaeologists found the three teeth at Çatalhöyük, a neolithic site in Turkey regarded by UNESCO as the most significant human settlement documenting early settled agricultural life. 

What’s more, researchers believe that Çatalhöyük, which was home to up to 8,000 inhabitants, was one of the very first egalitarian societies, as evidenced by distinctive homes, arranged back-to-back without doors or windows and the lack of monumental constructions (i.e. common burial grounds, temples, grand communal buildings). To get inside their homes, the inhabitants would use an opening through the roof which they would access via ladders.

At Çatalhöyük, archaeologists have found all sorts of artifacts, mainly tools. There are still many mysteries surrounding the site, including its sudden downfall. It’s believed that only 4% of the site has been excavated. During one recent dig, researchers found the three ornamental teeth.

Two of the teeth, a permanent premolar and a permanent molar, were found inside one of the dwellings at the site. The third, another permanent premolar, was found in a grave. All teeth came from adult individuals and showed no signs of disease, suggesting that they were likely removed post-mortem. Concerning their age, scientists have dated the teeth to sometime between 6300 and 6700 BCE.

Credit: Pixabay.

Researchers took silicone casts of the teeth to examine their wear and also employed microscopic and radiographic analyses in order to determine how the holes were drilled. The holes present in two of the teeth exhibited clear signs of intentional drilling. The hourglass-shaped holes suggest that the craftsman drilled from each side. After this procedure, the molars were polished. Wear on the inside of the hole suggests that the teeth were threaded in order to be worn as ornamentation.

It’s not clear at this point what ritualistic meaning this practice might have had — if there was any to begin with. Perhaps the teeth belonged to a deceased relative or high-status person which the wearer held in high regard. Perhaps they came from enemies. We can only speculate in the absence of more artifacts.

“The rarity of such artifacts in the prehistoric Near East suggests a profound symbolic meaning for this practice and these objects, and provides new insights into the funerary customs and symbolic importance of the use of human body parts during the Neolithic of the Near East,” the researchers wrote in the Journal of Archaeological Science: Reports.

Some people have extra bones, teeth, and even nipples. Here are some examples


The red arrow points to the fabella. Jmarchn and Mikael Häggström/Wikimedia CommonsCC BY-SA

Scientists in the UK recently reported that a bone that was thought to be lost to evolution is making a comeback. The little bone, known as the fabella (little bean), is found at the back of the knee – if it is found at all. The scientists discovered that people were nearly three-and-a-half times more likely to have the bone in 2000 than in 1900. Its exact purpose, however, remains a mystery.

The fabella is not the only variation in human anatomy. Variants occur as a result of genetics, environmental factors, mistimings in embryological development, or simply a failure of structures to disappear as part of normal development. Most variations are benign and don’t cause disease. Here are some of those that are well known to us anatomists…

Teeth


X-ray of person with supernumerary teeth.Albert/Wikimedia Commons

People have 20 primary teeth (“milk teeth”), which are lost and replaced by 32 permanent teeth. But up to 2% of people have extra teeth. Most of these people have one or two extra (supernumerary) teeth, but there are medical reports of people with many more extra teeth, with one female having 19 supernumerary teeth.

Nipples

Males and females have nipples because, early on in development, before the sex of the foetus has been determined, two ridges of tissue form, running from the front of the armpits to the groin. These ridges are known as mammary ridges.

Over time, both disappear to leave a single area where the mammary gland and nipple develop. It is possible for people to have supernumerary nipples, known as polythelia, along these lines, not in the middle of the chest between the existing nipples, as depicted in some TV and film shows. There are reports of people with seven nipples.

Digits

Most people have ten fingers and ten toes, but many people are born with extra digits. They are most commonly seen on the hands and are usually associated with disorders, such as Down syndrome.

Some ethnic groups are more likely to have extra digits than others. African-Americans have a much higher presence of an ulnar polydactyly – a digit on the little finger side of the hand. Caucasians have a higher presence of an additional digit on the radial (thumb) side of the hand, known as radial polydactyly. But this is less common.

While most people with extra digits have one or two, there are reports of people with 31 and even 34 digits.

Muscles

Muscles can also vary from one person to another. One of the easiest to observe (or observe its absence) is a muscle called palmaris longus. The best way to see if you have this muscle is to put your thumb and ring finger together and then bend your hand towards you. If you have this muscle, you should see a tendon pop up out of the wrist, running from the forearm and into the hand.

Testing for the palmaris longus muscle.

This muscle can be in one or both arms. In some people, it is absent in both. It is absent in both arms in about 10% of Caucasians and absent in one arm in 16%.

There are suggestions of an evolutionary loss of this muscle, with mammals such as orangutans, who use their arms for walking, having this muscle, but higher apes, such as gorillas and chimpanzees, showing an absence.

The good news for those of us who don’t have it is that it doesn’t make our grip strength weaker compared with those who have it. Although those who do have it may find it useful if surgeons ever need to repair a tendon, as the palmaris tendon is easily accessible and can be harvested for grafting.

There is a similar muscle in the lower leg called plantaris. It is believed to be absent in 7-20% of limbs. This muscle cannot be seen without using imaging, such as ultrasound, as it lies deep in the calf region of the leg. But like its variably present compatriot in the arm, it can be used for tendon grafting if needed.

Uterus

Some variations only come to light as people age, such as men born with a uterus. This developmental anomaly may only become manifest during puberty, with blood appearing in the urine. This is actually the menstrual cycle exiting through the urinary system.

All of this goes to show that human anatomy is not as clear-cut as school textbooks might suggest. We’re as variable as snowflakes. Something to be celebrated, surely.

Adam Taylor, Director of the Clinical Anatomy Learning Centre and Senior Lecturer, Lancaster University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

The Conversation
Teeth.

Our immune systems may actually help create cavities, a new study finds

Researchers in the University of Toronto’s Faculty of Dentistry have found evidence that our own bodies could be the major driver of tooth decay and filling failure.

Teeth.

Image via Pixabay.

The study shows how the decay of dentin (the hard substance beneath our teeth’s enamel) and fillings isn’t the work of bacteria alone. Rather, they report, it’s the product of an unintentional ‘collaboration’ between bacteria and immune cells known as neutrophils. As these two do battle, our teeth suffer the collateral damage.

Carpet bombing

“No one would believe that our immune system would play a part in creating cavities,” says Associate Professor Yoav Finer, the lead author of the study and the George Zarb/Nobel Biocare chair in prosthodontics at the Faculty of Dentistry. “Now we have evidence.”

Neutrophils are a type of short-lived immune system cells that play an important role in combating inflammation throughout the body. These cells make their way into the oral cavity via the gums around our teeth, where they fight off any bacterial invaders. But as they track and engage these bacteria, neutrophils also inflict damage on the surrounding environment.

“It’s like when you take a sledgehammer to hit a fly on the wall,” Finer says. “That’s what happens when neutrophils fight invaders.”

Byproducts of these engagements are the problem, the team explains. On their own, neutrophils can’t cause meaningful damage to teeth; these cells can’t produce any acid to attack the mineral-rich compounds. However, as they engage in an attack, oral bacteria do employ acids in a bid to defend themselves — and these demineralize teeth.

It’s here that the problem starts. The now-weakened teeth become susceptible to enzymes released both by bacteria and neutrophils, and these enzymes start boring through the demineralized area of teeth and tooth-colored fillings. Dentin and tooth-colored fillings sustain damage “within hours” of a bacteria-neutrophil showdown, the team reports. The research helps better explain why so many patients who had cavities filled with tooth-colored fillings face high rates of recurrence of the cavities. Most tooth-coloured fillings fail within five to seven years, costing Canadians an estimated $3 billion a year, the paper explains.

“It’s a collaboration of destruction – with different motives,” says study author Michael Glogauer, professor of the Faculty of Dentistry and acting chief dentist at the Princess Margaret Cancer Centre.

“Ours is the first basic study to show that neutrophils can break down resin composites (tooth-coloured fillings) and demineralize tooth dentin,” says master’s student and first author of the paper, Russel Gitalis. “This suggests that neutrophils could contribute to tooth decay and recurrent caries.”

While the findings may seem bleak, they actually point the way towards new potential treatment strategies. The findings may also help us develop new filling materials and test their resilience in the lab, potentially leading to much more durable fillings.

The paper “Human neutrophils degrade methacrylate resin composites and tooth dentin” has been published in the journal Acta Biomaterialia.

Fossil monkey teeth.

Fossil Friday: Newly-found fossil teeth solve ancient monkey mystery

Fossil teeth uncovered in Kenya, Africa, fill a missing link in the evolution of old world monkeys, a new paper reports.

Fossil monkey teeth.

Some specimens of A. metios that the team recovered.
Image credits D. Tab Rasmussen et al., (2019), PNAS.

The 22-million-year-old chompers allowed the team to describe a new species — which they christened Alophia metios — that fills a major gap in the evolution of old world monkeys (family Cercopithecidae), a team of U.S. and Kenyan researchers reports. It forms a link between a 19-million-year old fossil tooth unearthed in Uganda and a 25-million-year-old fossil tooth found in Tanzania.

Surprisingly, the teeth exhibit more primitive features compared to those of earlier species of monkeys, giving us an unique glimpse into what the lineage dined on in its earliest days.

Kenya find me a tooth?

“For a group as highly successful as the monkeys of Africa and Asia, it would seem that scientists would have already figured out their evolutionary history,” said the study’s corresponding author John Kappelman, an anthropology and geology professor at The University of Texas at Austin.

“Although the isolated tooth from Tanzania is important for documenting the earliest occurrence of monkeys, the next 6 million years of the group’s existence are one big blank. This new monkey importantly reveals what happened during the group’s later evolution.”

The team had their sights set specifically on the fossil-rich region of West Turkana, as the time interval they were interested in studying is only represented by a handful of African fossil sites. West Turkana is very arid today, but between 19 and 25 million years ago it was peppered with lush forest and woodland landscapes fed by a network of river and streams. Hundreds of mammal and reptile jaws, limbs, and teeth were recovered during fieldwork, ranging from 21 million to more than 24 million years old — including remains of early elephants.

At first, A. metios’ teeth confused the team. The fossil teeth were very primitive, more primitive than geologically younger monkey fossils, in fact. They even lacked a hallmark structure of monkey teeth, “lophs” — which are a pair of molar crests.

Fossil teeth comparison.

A comparison of cercopithecoid dental evolution over time. Specimens arranged left to right from oldest to youngest species. A are Alophia teeth, B are the same but reversed for comparison. C is Noropithecus, D is Victoriapithecus, E is Nsungewepithecus, F and G Alophia and Alophia reversed, H are Noropithecus teeth in reverse, I are Victoriapithecus teeth in reverse.
Image credits D. Tab Rasmussen et al., (2019), PNAS.

“These teeth are so primitive that when we first showed them to other scientists, they told us, “Oh no, that isn’t a monkey. It’s a pig,” said Ellen Miller, an anthropology professor at Wake Forest University and paper co-author.

“But because of other dental features, we are able to convince them that yes, it is in fact a monkey.”

The species’ name, Alophia, is a tribute to this feature — the word means “without lophs”. It’s quite a significant result, actually, since these lophs are a key feature of monkey teeth today. Lophs and cusps on molars allow the animals to eat a wide range of foods, from animal to plant matter. These teeth are like “uber food processor[s]”, the team explains, and helped monkeys adapt to the diverse environments they inhabit today, from Africa to Asia.

Exactly how and when these structures evolved, however, remained a mystery.  The researchers speculate that Alophia’s primitive dentition was suited to a diet of hard fruits, seeds, and nuts — but not leaves, as these are more efficiently processed by teeth such as those first seen in monkeys from 19 million years ago. This would suggest that the later inclusion of leaves in the diet of monkeys was a key driver of their (and their dental) evolution

“It is usually assumed that the trait responsible for a group’s success evolved when the group originated, but Alophia shows us this is not the case for Old World monkeys,” says co-author Samuel Muteti, a researcher at the National Museums of Kenya.

“Instead, the characteristic dentition of modern monkeys evolved long after the group first appeared.”

Monkeys as a lineage first appeared during a time when Africa and the Arabian peninsula were still joined together. Species here evolved in relative isolation until the whole island-continent connected to Eurasia, between 20 to 24 million years ago. After this time, we see mammals such as antelope, pigs, lions, or rhinos — what we’d consider African species today — making their way to Africa and Arabia.

One of the team’s hypotheses is that these immigrant species placed a lot of environmental stress on monkeys, and competition between them and the new arrivals drove monkeys to start exploiting leaves as a food source. Alternatively, changing climate conditions could have been at the root of this dietary shift.

“The way to test between these hypotheses is to collect more fossils,” Kappelman said. “Establishing when, exactly, the Eurasian fauna entered Afro-Arabia remains one of the most important questions in paleontology, and West Turkana is one of the only places we know of to find that answer.”

The paper “Primitive Old World monkey from the earliest Miocene of Kenya and the evolution of cercopithecoid bilophodonty” has been published in the journal Proceedings of the National Academy of Sciences.

Megalodon.

Megalodon’s teeth evolved over 12 millions years, researchers find

These “ultimate cutting tools” were a long time in the making.

Megalodon.

Teeth are the only reliably identifiable fossils from Carcharocles megalodon. They’re also damn huge.
Image credits Kristen Grace / Florida Museum of Natural History.

The teeth of megalodon (Carcharocles megalodon), the largest shark ever to prowl the oceans, look like daggers. They’re up to 7 inches (18 cm) long and shaped like blades. But it took them millions of years to evolve into their final shape, new research reveals. The findings created more questions than they answered, as we still don’t know why the process took so long or why it started in the first place.

Big fish, bigger bite

“This transition was a very long, drawn-out process, eventually resulting in the perfect cutting tool — a broad, flat tooth with uniform serrations,” said study lead author Victor Perez, a doctoral student in geology at the Florida Museum of Natural History.

“It’s not yet clear why this process took millions of years and why this feature [serration] was lost.”

Megalodon has to be one of the most awe-inspiring and mysterious animals out there. It was the largest shark ever seen on Earth, but the only trace they’ve left is their teeth. Which is quite fitting for a shark.

But these teeth, according to Perez’s team, evolved over 12 million years. The researchers analyzed the evolutionary path of megalodon teeth and those of its immediate ancestor, Carcharocles chubutensis. Their study revealed a surprisingly slow and gradual process, in which they shifted from large teeth flanked by cusplets to regular, cusplet-less teeth.

The team performed a “census of teeth,” analyzing 359 fossils along with the precise location of their retrieval at the Calvert Cliffs on the western shore of Maryland’s Chesapeake Bay — an area that used to be an ocean in C. chubutensis and megalodon’s day.

Megalodon’s earliest ancestor, Otodus obliquus, boasted three-pronged teeth (i.e. teeth with cusplets) that acted more like forks, the team writes. This suggests that O. obliquus dined on fast-moving (but not too large) fish, and it needed teeth to pin them in place. This species effectively forms the baseline from which later megatooth shark species derived.

The fossil record at Calvert Cliffs spans from about 20 to 7.6 million years ago, so they overlap with both C. chubutensis and megalodon. Perez’s team found a consistent decrease in the number of teeth with lateral cusplets over this timespan. About 87% of teeth from 20 to 17 million years ago had cusplets, falling to about 33% roughly 14.5 million years ago. By 7.6 million years, no fossil teeth had cusplets.

But here’s where the results start getting muddy. While the team notes that adult C. chubutensis had cusplets, and adult megalodon did not, they also caution that this feature is not a reliable identifier of which species a tooth belonged to — juvenile megalodon could have cusplets, making it virtually impossible to discern whether a tooth with cusplets came from C. chubutensis or a young megalodon. Furthermore, some teeth analyzed for the study had tiny bumps or pronounced serrations where cusplets would be. A set of teeth from a single shark even had cusplets on some, no cusplets on others, and replacement teeth with reduced cusplets.

While definitely interesting from a paleontological and biological point of view, such specimens make it virtually impossible for the team to draw clean lines between different species. They can’t pinpoint when megalodon first appeared or when C. chubutensis went extinct.

“As paleontologists, we can’t look at DNA to tell us what is a distinct species. We have to make distinctions based off of physical characteristics,” says Perez. “We feel it’s impossible to make a clean distinction between these two species of sharks. In this study, we just focused on the evolution of this single trait over time.”

So what can the study, then, tell us? Well, it does help to flesh out our understanding of how later megatooth species (such as megalodon) lived, how they hunted, and a bit or two about how they handled disease.

Megalodon fossils have flat teeth, often with serrated edges. Based on their shape, they likely performed a different job than that of its earliest ancestor: that of killing (or at least, mortally wounding) large, fleshy animals like whales or dolphins. Megalodon likely hunted in a single-strike manner: it charged at its prey and chomped down hard. Whatever didn’t die on the spot was left immobilized or too crippled to run away, and bleeding heavily.

“It would just become scavenging after that,” says Perez. “A shark wouldn’t want to grab and hold onto a whale because it’s going to thrash about and possibly injure the shark in the process.”

Lateral cusplets may have been used to grasp prey, according to Perez, which could explain why they disappeared as these sharks shifted to a new hunting style. It’s also possible that the cusplets kept food out from between the sharks’ teeth — so they helped prevent gum diseases. But, frankly speaking, the team simply doesn’t have enough information to know why these structures evolved out of the shark’s teeth.

“It’s still a mystery,” Perez says. “We’re wondering if something was tweaked in the genetic pathway of tooth development.”

One point I found particularly interesting was how important ‘beachcombers’ were for this study. The team says that vast majority of teeth they analyzed were discovered by amateur fossil collectors and donated to museum collections.

“This study is almost entirely built on the contributions of amateur, avocational paleontologists,” Perez notes. “They are a valuable part of research.”

The paper “The transition between Carcharocles chubutensis and Carcharocles megalodon (Otodontidae, Chondrichthyes): lateral cusplet loss through time” has been published in the Journal of Vertebrate Paleontology.

Mammaliaform Morgauncodon

Mammals’ evolutionary success relied on our ancestors growing very tiny

Mammals cashed in big on growing smaller, new research reveals.

Mammaliaform Morgauncodon

Morganucodon, a mamaliaformes and one of the best-preserved species from which all mammals originate, grew up to only 4-6 cm length.
Image credits Bob Nicholls.

The bubbly evolution of mammal species over the last 200 million years is owed in no small part to their propensity for growing smaller, a new paper reports. This trend is most evident when compared to that of the dinosaurs — the former de-facto winners of the evolutionary lottery — which spawned some of the largest beasts to ever walk the Earth.

Smaller, better, harder, stronger

When mammals first started popping up around 200 million years ago, our planet was still dominated by dinosaurs. So for the following 150-ish million years, mammals literally and figuratively kept a low profile. While dinosaurs were growing bigger, mammals shrank in size.

An international team of researchers set out to understand why and how this shift took place. Using modern computer modeling and analysis, they analyzed the skeletons of our tiny ancestors to better document their evolutionary path.

Mammals stand out among all other vertebrates on the planet in that they have a single bone bearing teeth for their lower jaw. Everyone else has more complex lower jaws, formed from no fewer than five bones linked together, the team explains.

As mammals evolved, most of these bones shrank in size and became more simplified. The new jaw retained a single bone, and the others moved higher in the skull, into the inner ear. They now help us hear.

The team focused their research efforts on understanding how this lower jaw restructuring process took place — as they were occurring, these changes had to allow the animal to keep feeding itself and hear, else they wouldn’t be viable organisms. Starting from X-ray computed tomography (CT) scans of several fossil skulls and lower jaws, the team created digital models of the bones. Later, they ran these models through extensive computer simulations to see how they would function.

For smaller animals, the team reports, jaw bones experience reduced stress when feeding. The jaws themselves could thus become simpler and tinier while still retaining enough structural strength to bite through prey.

“Our results provide a new explanation of how the mammalian jaw evolved over 200 million years ago,” says Dr Stephan Lautenschlager, lead author of the paper and lecturer at the University of Birmingham.

“Getting very small appears to have been crucial for our mammalian ancestors. This allowed them to reduce the stresses in the jaw during feeding and made the restructuring of the jaw bones possible.”

University of Bristol Professor Emily Rayfield, who co-authored the study, says that the research addresses a 50-year-old open debate in paleontology.

“Using computational methods we can offer explanations to how our mammalian ancestors were able to maintain a working jaw while co-opting bones into a complex sound detection system,” she explains. “Our research is about testing ideas of what makes mammals unique among the animal kingdom, and how this may have come about.”

The paper “The role of miniaturisation in the evolution of the mammalian jaw and middle ear” has been published in the journal Nature.

P. robustus skull.

One of our extinct ancient relatives developed a chewing pattern unique among primates

Not all human ancestors chewed the same way, new research reveals.

P. robustus skull.

Paranthropus robustus fossil from South Africa SK 46 (discovered 1936, estimated age 1.9-1.5 million years) and the virtually reconstructed first upper molar used in the analyses.
Image credits Kornelius Kupczik / Max Planck Institute for Evolutionary Anthropology.

While we’re the only one that made it up to the present, we’re by no means the only species of hominins — the evolutionary group that includes modern humans and now-extinct bipedal relatives — that popped up throughout history. At least one of our human ancestors, new research shows, developed a unique way to chew.

Ancient chow

Being able to properly chew your food is a matter of life and death. It helps break food down into tiny pieces so they can be swallowed and digested. But every species has its own way of going about it — based on their diet and individual morphology.

You can learn a lot about an animal by looking at what it eats and the way it chews on it, and that stands true for humans as well as wildlife. Palaeoanthropologists go to great lengths to reconstruct the diets of ancient hominid species, as diet underpins our evolutionary history. A high-quality diet, for example, coupled with meat-eating, provided the nutrients that modern humans needed to develop our big brains. Some of our hominin relatives, by contrast, likely went extinct because of their diets (for example, the Neanderthals).

Two extinct hominin lineages — Australopithecus africanus and Paranthropus robustus — have constantly sparked debate in regards to their diet since their discovery. An international team of researchers, led by members from the Max Planck Institute for Evolutionary Anthropology, studied the splay and orientation of their fossil tooth roots in an attempt to settle the debate once and for all. Their findings surprisingly reveal that P. robustus employed a unique way of chewing food — one that hasn’t been seen in any other hominin species to date.

The team used high-resolution computed tomography and shape analysis to determine how teeth roots were oriented within the jaw of ancient hominin lineages. Based on this information, they then gauged the direction of the load during mastication — i.e. the direction force was applied while they chewed.

By comparing the virtual reconstructions of 30 hominin first molars from lineages in South and East Africa, the team found that Australopithecus africanus had much more widely-splayed roots than either Paranthropus robustus or the East African hominin Paranthropus boisei. This yielded a surprising revelation about P. robustus.

“This is indicative of increased laterally-directed chewing loads in Australopithecus africanus, while the two Paranthropus species experienced rather vertical loads,” says Kornelius Kupczik of the Max Planck Institute for Evolutionary Anthropology, first author of the paper.

Unlike all other hominins involved in the study, P. robustus showed a ‘twist’ in the roots of their teeth — suggesting a slight rotational and back-and-forth movement while chewing, the team explains. Other characteristics of their skulls support this observation, they add: the structure of the enamel also points towards a complex, multi-directional motion. Microwear patterns in the enamel (which the team reports are “unique among primates”) also point to a different motion of the jaw while masticating compared to how we do it, for example.

While diet also has a major part to play in shaping our and P. robustus‘ skulls, as well as in the patters of wear observable on their teeth, the team says dietary differences alone cannot account for all that they’re seeing.

“Perhaps palaeoanthropologists have not always been asking the right questions of the fossil record: rather than focusing on what our extinct cousins ate, we should equally pay attention to how they masticated their foods,” concludes co-author Gabriele Macho of the University of Oxford.

The research could have implications beyond paleoanthropology, the team explains. By studying the particularities of P. robustus‘ morphology, its mastication patterns, and its effect on the lineage’s teeth, “we can eventually apply such findings to the modern human dentition to better understand pathologies such as malocclusions,” explains co-author Viviana Toro-Ibacache.

The paper “On the relationship between maxillary molar root shape and jaw kinematics in Australopithecus africanus and Paranthropus robustus” has been published in the journal Royal Society Open Science.

Llanocetus denticrenatus

Early baleen whales were fearsome predators with wicked teeth, but lost them entirely

Baleen whales (parvorder Mysticetes) haven’t always been ‘baleen’, new research shows — and this unique adaptation hasn’t evolved from teeth, as previously suspected.

Llanocetus denticrenatus

A reconstruction of Llanocetus denticrenatus.
Image credit Carl Buell.

Today’s baleen whales are truly distinctive. Their most distinctive feature, the baleen — the comb-like filter-feeder system such whales use to capture krill — is so unique, we’ve used it to name the whole group. According to new research, however, the group didn’t always sport this specialized feeding apparatus. Just 34 million years ago, they were using good ol’ fashion teeth to do some good ol’ fashioned chomping with, one fossil reveals.

Teethy giants

“Llanocetus denticrenatus is an ancient relative of our modern gentle giants, like humpback and blue whales,” says lead author Felix Marx of the Royal Belgian Institute of Natural Sciences. “Unlike them, however, it had teeth, and probably was a formidable predator.”

Although you wouldn’t tell by their girth, whales actually originate from land mammals. Because of this, researchers knew the whales had to pick up filter-feeding after retreating back to the oceans (since you can’t really filter-feed on land). Up until now, common wisdom held baleen whales first started filter-feeding back in the days they still had teeth, but this may not have been the case.

Skull.

Skull of Llanocetus denticrenatus. (A) Dorsal view. (B) Ventral view.
Image credits R. Ewan Fordyce, Felix G. Marx, (2018) / Current Biology.

Just like modern whales today, Llanocetus denticrenatus sported a series of distinctive grooves on the roof of its mouth (palate), the team reports. These grooves create the space necessary for blood vessels that supply the baleen in present-day Mysticetes. In Llanocetus, however, the grooves are clustered around teeth sockets — which suggests that they were feeding gums and teeth, not baleen. Baleen is fragile and would have been too exposed in such areas, liable to be crushed. Instead, the Marx suspects that the beast “simply had large gums and, judging from the way its teeth are worn, mainly fed by biting.”

Given that Llanocetus could grow to about 8 meters (26.2 feet), it likely had to do a lot of biting to keep reasonably fed. Thankfully for it, it came equipped for the job, the team finding a row of sharp, widely-spaced teeth with marked wear embedded in its rostrum.

I asked Ewan Fordyce, Professor at the Department of Geology at the University of Otago, New Zealand and paper co-author about what Llanocetus‘ meals likely consisted of. He admits that the team is “not sure” yet what this toothy whale hunted, but that its anatomy can yield some clues:

“It was probably not a top predator, Because these small teeth could only deal with medium-sized prey,” he told ZME Science in an e-mail. “It ate prey that was processed in part at least by teeth that could shear and pierce. Perhaps took small to medium-sized fish, not too bony, and maybe squid.”

Feeding apparatus

Feeding Apparatus of Llanocetus denticrenatus.
Image credits R. Ewan Fordyce, Felix G. Marx, (2018) / Current Biology.

The team’s findings suggest that baleen actually evolved from the gums, not the teeth themselves. The soft tissue gradually became more complex over evolutionary time and developed into the baleen, the team writes. This transition likely happened after the whales had already lost their teeth, and switched from biting larger victims to slurping in small pray. Marx and Fordyce believe that baleen evolved as a way to more effectively keep such prey inside the animals’ mouth — meaning they had to already be doing it for evolution to favor the baleen.

One factor that could be behind this change of menu is simple economics:

“Felix and colleagues have made the point that by feeding on small food, baleen whales move down the food chain,” Fordyce added for ZME Science, “[where] they have more resources than if they were at the top of the food chain.”

The results show that the evolution of baleen whales was more convoluted than previously thought, the team says. Next, they’ll try to get a better understanding of the baleen whales’ evolutionary path.

The paper “Gigantism precedes filter feeding in baleen whale evolution” has been published in the journal Current Biology.

Credit: Wikimedia Commons.

What causes cavities and how to spot tooth decay

Credit: Wikimedia Commons.

Credit: Wikimedia Commons.

A cavity is basically a hole in the tooth. Cavities, also called caries or tooth decay, constitute the second most common health disorder in the western world and a common cause of tooth loss in young people around the world. Cavities start small and gradually become bigger when they’re left untreated.

People who are at the highest risk of developing cavities include low-income families, seniors, people who drink non-fluoridated water, people undergoing radiotherapy, diabetes patients, smokers, alcohol and drug users, and people who consume large amounts of sugary drinks.

What causes cavities

According to a recent National Institutes of Health (NIH) estimate, 90% of cells in the human body are bacterial, fungal, or otherwise non-human. The good news is that most of these bacteria are harmless, and some are even beneficial. The bad news is that some cause all sorts of health problems, including oral diseases like cavities and periodontal disease. These bacteria are incredibly tiny, measuring only 1/500th of a human hair in width but what they lack in size, they make up for in numbers. By one estimate, there are at least 300 different species of bacteria living inside your mouth, totaling more than a billion at any given time.

When you’re having lunch or dinner, it’s not just you that’s feeding. All that bacteria inside your mouth is having a picnic too, munching on the sugars in the foods and drinks that we consume. But what goes in, must come out. After they’ve had their snack, the bacteria will excrete waste in the form of a biofilm that your dentist calls dental plaque. If plaque stays on the teeth for more than a few days, it hardens and becomes a substance called tartar.

The plaque is what allows the microorganisms to stay on your teeth for longer, until they make acids, which wear down the tooth enamel. After the enamel is worn out, the acid reaches the next layer of the tooth, called dentin, which is softer and far more susceptible to acid than enamel. Finally, the bacteria and their acid reach the pulp. This is what eventually will get you cavities. The bacteria in the plaque will also attack the gums, causing gingivitis. If left untreated, gingivitis can evolve into periodontitis, a far more serious condition where there is bone and tissue loss around the teeth.

Besides sugar, other foods that cause the bacteria in your mouth to produce acids are starches — such as bread, crackers, and cereal.

What’s more, the bacteria that cause cavities are spreadable. Yes, tooth decay is actually an infectious disease and according to a study published in the journal Microbiome, an otherwise innocent ten-second French kiss can spread 80 million bacteria between mouths!

Cavities are most commonly found where plaque forms the most easily, such as on the molars, between teeth, near the gum line, and at the edges of fillings.

What do cavities look like

More than nine out of 10 American adults have cavities, according to the National Center for Health Statistics (NCHS), and more than a quarter of American adults have untreated tooth decay.

It’s extremely important that you visit a dentist regularly have radiographs of your teeth. Because early cavities don’t pose symptoms, you might not realize you have tooth decay until it may be too late, i.e. the cavity gets too big. Some signs that you may have cavities are discolored spots on the tooth and sensitivity to cold.

In the later stages of a cavity, the pulp, which is the nerve, is visible. This makes the tooth sensible to heat, cold, sweets, and drinks. If the decay progresses long enough, parts of the tooth may fall off and the tooth may become highly sensitive to pressure. Bad breath and bad taste in the mouth are also symptoms of late cavities.

The three main types of cavities

Credit: AllizHealth.

Root cavities

Root cavities are most commonly found in older adults, who are more likely to have receding gums and other gum disorders. Receding gums expose the roots of the teeth, which become vulnerable to tooth decay now that there’s no more hard enamel to shelter them. To treat a root cavity, the decay is first removed and the hole in the tooth is plugged with a filling or crown. In extreme cases when the decay has spread to the pulp, root canal treatment is advised. A root cavity needs to be fixed as soon as it’s detected because the damage spreads quicker than in other areas of the tooth where the enamel is tough.

Pit and fissure cavities

Pit and fissure cavities appear on the chewing surfaces of teeth, most commonly on the back teeth. Most often, this type of decay is due to inconsistent and careless oral hygiene habits. This is a very common type of cavity because it’s easy for food particles and plaque to get stuck in the grooves and crevices present on the top of the teeth. If detected early, pit and fissure cavities can be treated with a good fluoride toothpaste. However, if the decay reaches the dentin, the cavity needs to be removed and the tooth repaired with fillings, composites, or crowns.

Smooth-surface cavities

Smooth-surface cavities appear on the flat exterior surface of teeth and are most commonly found on the teeth at the sides of the mouth. They occur when people do no brush correctly or regularly. These are the slowest-growing cavities and also the least common. Because this type of decay grows slowly, it’s also the easiest for a dentist to treat. Some may not need filling at all and can instead be fixed with fluoride treatments like toothpaste, gels, varnishes, or fluoride-enriched water.

How to prevent cavities

In order to keep oral bacteria in check, we need to manage them through proper oral hygiene, healthy diet, and regular dental checkups.

[panel style=”panel-info” title=”How to brush your teeth” footer=”Brushing technique recommended by the American Dental Association. “]

  • Place your toothbrush at a 45-degree angle to the gums.
  • Gently move the brush back and forth in short (tooth-wide) strokes.
  • Brush the outer surfaces, the inner surfaces, and the chewing surfaces of the teeth.
  • To clean the inside surfaces of the front teeth, tilt the brush vertically and make several up-and-down strokes.

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Brushing after meals, using antimicrobial mouthwash, and flossing helps to keep these disease-causing bacteria from reproducing in your mouth, and from causing tooth decay. The American Dental Association (ADA) recommends you:

  • Brush your teeth twice a day with a soft-bristled brush. The size and shape of your brush should fit your mouth allowing you to reach all areas easily.
  • Replace your toothbrush every three or four months, or sooner if the bristles are frayed. A worn toothbrush won’t do a good job of cleaning your teeth.
  • Make sure to use an ADA-accepted fluoride toothpaste.

Credit: AllizHealth.

Fluoride mouth rinses also help reduce and prevent tooth decay; but you should always talk to your dentist about any new products you are interested in trying, because not everyone should use a fluoride mouth rinse.

Because there is little scientific evidence that suggests flossing keeps teeth and gums healthy, the Department of Health and Human Services has dropped their recommendation to floss daily. Many dental practitioners still advise patients floss their teeth daily, nevertheless.

In terms of diet, minimizing sugary and starchy food are important for keeping bacteria at bay.

So, how long has it been since your last checkup?

 

This illustration shows puncture-and-pull feeding in predatory theropod dinosaurs, based on the results of the researchers' microwear analysis and finite element analyses. Credit: Sydney Mohr.

How tooth wear sheds light on the predatory lives of dinosaurs

This illustration shows puncture-and-pull feeding in predatory theropod dinosaurs, based on the results of the researchers' microwear analysis and finite element analyses. Credit: Sydney Mohr.

This illustration shows puncture-and-pull feeding in predatory theropod dinosaurs, based on the results of the researchers’ microwear analysis and finite element analyses. Credit: Sydney Mohr.

There’s a lot you can learn about a dinosaur from their teeth alone. Predatory, bird-like theropod dinosaurs, for instance, all used a puncture-and-pull bite strategy to kill and devour their prey. However, an international team of researchers analyzed the wear and various denticle shapes of such dinosaurs, concluding that some of these predatory dinosaurs were more suited for larger, struggling prey, while others preferred to handle softer, smaller prey.

It’s all in the teeth

Angelica Torices, the lead author of the new study and a postdoc at the University of Alberta, Canada, has always been interested in carnivorous dinosaur teeth. At first, her work involved matching dinosaurs species with various teeth. Later, the main question surrounding her work moved from ‘who’ or ‘why.’

Previous studies, typically performed on mammals, were able to infer biting movements and types of diets simply by studying the scratches and pits on teeth. Torices and colleagues decided to do the same for the two types of predatory coelurosaurian dinosaurs — bird-like therapods that lived during the Upper Cretaceous between 100 million and 66 million years ago.

The analysis showed that all coelurosaurian dinosaurs bite in the same way through a puncture-and-pull system, but troodontids and dromaeosaurids may have preferred different prey. Specifically, troodontids apparently favored requiring lower bite forces in comparison to dromeosaurs.

“The fact that there was a shape that was more widespread than the other two led me to think that, maybe, there was a difference in efficiency between those different denticle shapes so I decided to test it. It was challenging because nobody had looked at that particular problem before in carnivorous dinosaurs so there was not much literature about it,” Torices told ZME Science.

This figure shows different theropod dinosaurs, their teeth, and their different denticle shapes. All teeth are scaled to the same crown height for comparative purposes. Credit: Victoria Arbour.

This figure shows different theropod dinosaurs, their teeth, and their different denticle shapes. All teeth are scaled to the same crown height for comparative purposes. Credit: Victoria Arbour.

At first, Torices examined the microwear of various dino tooth fossils, looking for any pattern that might give off what the owners of the teeth were eating. Then, Torices and colleagues at the University of Alberta employed a finite element analysis — a numerical method for solving problems of engineering and mathematical physics — to see how the denticles and the tooth behaved under different cutting angles.

“I was very surprised how the finite element analysis confirms the results of the microwear analysis. It shows that the three types of denticles are optimized for the cutting angle employed during the ‘puncture-and-pull’ mechanic. However when these teeth were biting at non-optimal cutting angles the three denticle morphologies behaved differently regarding stress,” Torices told me.

Dromaeosaurus and Saurornitholestes were well adapted for handling struggling prey or for processing bone as part of their diet. Meanwhile, Troodon teeth were more likely to fail at awkward bite angles, which suggests they must have gone for softer prey such as invertebrates. Now, all of a sudden, we know that some groups of predatory dinosaurs — despite living during the same time and sharing the same ecological niche — weren’t likely in direct competition for the same prey. Not bad for some teeth.

“We have a lot to learn from teeth! Through these carnivorous dinosaur teeth we have been able to infer how they were biting and what type of prey they would be eating and the results show us that probably there were aiming for different food resources. Now we are working with more complex models including not only teeth but also roots and jaws to understand the interaction of all elements during the biting process,” Torices said.

The findings were reported in the journal Current Biology.

The first hominids might have evolved in Europe, fossil jaw suggests

A new paper examines whether Europe and not Africa was the cradle of hominids some 7 million years ago.

Greece Jaw.

This jaw and teeth were found in Greece and belonged to what might have been the oldest hominid.
Image credits W. Gerber / University or Tübingen.

The teeth of a chimp-sized primate known as Graecopithecus, which lived in southeastern Europe some 7 million years ago, suggests that the species is actually an early hominid and not an ape as we previously believed, a team led by geoscientist Jochen Fuss of the University of Tübingen, Germany, reports. They cite partial fusion of the second premolar root as a particular similarity between Graecopithecus and early hominids.

What makes a man

Graecopithecus could be the first hominid to pop up, the researchers write. One lower jaw, found in Athens with most teeth still in their sockets, was dated to about 7,175 million years ago, and a single upper second premolar found in Bulgaria, to approximately 7.24 million years ago. Still, with only these bits on hand, it’s hard to make an airtight case for Graecopithecus as a hominid. Although the dates match, it’s still a mystery if this creature walked upright — a hallmark of hominids.

So it’s still unclear whether Graecopithecus was an ape with hominid-like features or a hominid with some apelike characteristics. At the same time, however, the team notes that fossil evidence of humanoids in Africa around this time is also pretty sketchy, in some cases even controversial, and revolves around two hominid lines dating to between about 7 million and 6 million years ago, Sahelanthropus and Orrorin.

“Europe is as likely a place of [hominid] origins, and even of the last common ancestor of chimpanzees and humans, as Africa,” says University of Toronto paleoanthropologist and study co-author David Begun.

The team used a CT scanning device to view Graecopithecus’s teeth in full 3D, including the roots hidden by jawbone. Using this model to compare to other early hominids, they discovered the partial fusion of the second premolar root as a striking similarity. Previous research has found that the number of these roots is tightly controlled genetically and doesn’t change due to environmental factors — so the root fusion in Graecopithecus, similar to those seen in later hominids, would suggest a direct evolutionary link.

Model Teeth.

Image credits Jochen Fuss et al, PLOS ONE (2017).

The findings are not without their own criticisms. First of all, some say that the number of premolar roots varies enough even among early hominids to make the fused roots a less conclusive piece of evidence. But, when working with so few fossils from so long ago, it’s hard to prove anything conclusively — for example, the team which discovered one East African hominid, Ardipithecus kadabba, later argued that Sahelanthropus and Orrorin aren’t distinct lineages but can be folded into Ar. kadabba — and that’s not an isolated case.

A lack of hominid precursor (our chimp and gorilla ancestors) fossil, in particular, makes it difficult to establish if creatures such as Graecopithecus or Ar. kadabba are truly hominids since there’s nothing to compare them against. Finally, there was quite a bit of back-and-fro going on between Africa and Europe’s eastern Mediterranean region between 9 million and 7 million years ago, with apes, giraffes, antelopes, hippos, and a host of other critters living and transiting through the region or between the continents, Begun adds, making it hard to pinpoint where everyone came from. So Graecopithecus could have evolved in either Europe or Africa.

But if evidence mounts that Graecopithecus was a hominid and evolved in Europe, the out of Africa theory could find itself into even rougher waters.

The full paper “Potential hominin affinities of Graecopithecus from the Late Miocene of Europe” has been published in the journal PLOS One.

Oldest cavities.

World’s oldest fillings come from the stone age and they’re basically asphalt

People have been going to the dentist for a much longer time than you’d believe. Archaeologists working in northern Italy have found the oldest known dental fillings. They were made from a mix of bitumen, hairs, and plants some 13,000 years ago.

Oldest cavities.

Image credits Stefano Benazzi.

There’s no such thing as a good toothache. That’s why we have dentists, and that seems to have been the case in the stone age, too — although I hear conditions weren’t as good back in the day. Faced with a lack of materials, tools, or you know, any sort of body of literature to guide their steps, ancient dentists had to be creative (they invented a lot of stuff back then). A pair of 13,000-year-old front teeth found in Italy stands testament to what they could achieve with a bunch of stones and bitumen.

Asphalt teeth

The teeth were discovered in the Riparo Fredian site near Lucca, northern Italy. Each one has a large cavity going from the surface all the way through to the pulp. They were probably hollowed out and enlarged with stone tools, judging by microscopic etches and markings on their walls. While poking though these holes, a research team lead by Gregorio Oxilia from the University of Bologna has found residues of bitumen with plant fibers and hairs mixed in. Although very different from what you’d see in today’s fillings, their purpose was probably the same — keep stuff away from the pulp and keep pain to a minimum.

“It is quite unusual, not something you see in normal teeth,” Stephano Benazzi, an archaeologist at the University of Bologna and corresponding author of the paper told New Scientist.

Benazzi noted that the etchings found in these teeth are similar to another set him and the team found in Italy in previous research. That set of teeth was dated as 14,000 years old, the oldest known evidence of dentistry we’ve ever seen. But this is the (new) first time we know of fillings being used.

Fredian upper central incisors.

Image credits Gregorio Oxilia.

It’s probable that the Paleolithic dentist drilled out the cavities and then filled them in — just like his modern counterparts would do. However, he only had tiny stone tools to drill with, probably no anesthetics, and bitumen to use for the fill. The team is unsure as to why the hairs and plant fibers were added to the mix (they did rule out the possibility of them being remains of food since they were added to the area after drilling). One theory is that the plants were chosen for their antiseptic properties, helping to keep the cavity healthy and clean of bacteria. Or the dentists thought fibers would help fix the filling. We don’t yet know.

What’s really striking is the time-frame of the fillings. They’re evidence of relatively advanced knowledge being put to use in fixing an ailment thousands of years before we though they’d become a significant affliction — the change in diet agriculture brought on is thought to have lead to a dramatic increase in cavities. Still, at this time Europe was seeing a lot of people migrating in from the near East, Benazzi adds. The foods they introduced to the continent may have led to more cavities, and then to dentistry.

The full paper “The dawn of dentistry in the late upper Paleolithic: An early case of pathological intervention at Riparo Fredian” was published in the American Journal of Physical Anthropology.