Oldest cases of mammal tooth decay in 54-million-year-old fossils

Prehistoric primates had a sweet tooth! Squirrel-sized species that lived 54 million years ago gorged on sugary fruits — and had the first recorded cases of dental decay in mammals

  • Microsyops latidens was a tiny tree-dwelling primate from the Early Eocene
  • University of Toronto Scarborough experts studied 1,030 teeth and jaw fossils
  • These had all been unearthed from the Southern Bighorn Basin in Wyoming
  • Cavities appeared in 7.5% of fossils — a frequency higher than modern mammals
  • They also varied with time, suggesting changes in Microsyops latidens’ diet
  • The team believe that these shifts may have been causes by climatic changes

The earliest known cases of dental cavities in mammals have been found in a squirrel-sized species that lived 54 million years ago and gorged itself on sugary fruits.

Fossil specimens of the prehistoric tree-dwelling primate — Microsyops latidens — were analysed by researchers from the University of Toronto Scarborough.

They found that 7.5 per cent of all the fossils that they studied had cavities, with some layers containing a greater frequency than others.

This suggests that the diet of Microsyops latidens varied over time between foods with higher and lower sugar contents.

The earliest known cases of dental cavities in mammals have been found in a squirrel sized species that lived 54 million years ago and gorged itself on sugary fruits. Pictured: the dental cavities can be seen in this micro-CT reconstruction of Microsyops latidens’ upper jaw


As part of their study, the experts compared the prevalence of cavities in the fossils of Microsyops latidens with those of modern primates.

Microsyops latidens suffered more cavities than most primates today.

There are exceptions, however — specifically among the genus Cebus (which contains the capuchins) and Saguinus (e.g. tamarins).

The study was conducted by anthropologists Keegan Selig and Mary Silcox of the University of Toronto Scarborough.

‘Dental cavities or caries is a common disease among modern humans, affecting almost every adult,’ the duo wrote in their paper.

‘Caries frequency has been used to study dietary change in humans over time, based on an inferred tie between the incidence of caries and a carbohydrate-rich diet.

‘However, the disease is not unique to our species. Among non-human primates, there is also variation in caries frequency associated with diet.

‘This metric may provide a mechanism for studying diet in broader contexts, and across geological time.’ 

In their study, the researchers analysed a total of 1,030 individual fossil teeth and jaw sections that were unearthed in the Southern Bighorn Basin of Wyoming, in the US.

The team found that 77 of the specimens included dental cavities, which they say were likely caused by a diet that was high in fruit or other sugar-rich foods. 

However, by dating the fossils based on the age of the sediments in which they were deposited, the pair determined that the frequency of cavities varied over time, with the fewest found in the oldest and youngest of the specimens.

This suggests that the diet of Microsyops latidens changed over time between foods with varying levels of sugar content, perhaps in response to changes in vegetation growth and food availability brought about by the climate fluctuations of the time. 

‘Microsyops latidens may have relied on food sources that were higher in sugar, and therefore more cariogenic [likely to cause tooth decay], during periods of climatic flux,’ the researchers wrote in their paper. Pictured: a reconstructed slice through a cavity in a second molar

‘Microsyops latidens may have relied on food sources that were higher in sugar, and therefore more cariogenic [likely to cause tooth decay], during periods of climatic flux,’ the researchers wrote in their paper.

‘This, they explained, could have been ‘a result of increased competition for limited food sources, or a change in the food sources that were available. This, in turn, may have led to the noted increase in caries frequency.

‘As more palaeoclimatic data become available, it is possible that we will see evidence of further climatic change during this period, which may have affected the food sources available to M. latidens,’ they concluded. 

The full findings of the study were published in the journal Scientific Reports.

In their study, the researchers analysed a total of 1,030 individual fossil teeth and jaw sections that were unearthed in the Southern Bighorn Basin of Wyoming, in the US


Tooth decay is damage to a tooth caused by dental plaque turning sugars into acid.

If plaque is allowed to build up, it can lead to problems, such as holes in the teeth (dental caries) and gum disease.

Dental abscesses, which are collections of pus at the end of the teeth or in the gums, may develop.

Symptoms of tooth decay 

Tooth decay may not cause any pain.

But if you have dental caries, you might have:

  • toothache — either continuous pain keeping you awake, or occasional sharp pain without an obvious cause; it can sometimes be painless
  • tooth sensitivity — you may feel tenderness or pain when eating or drinking something hot, cold or sweet
  • grey, brown or black spots appearing on your teeth
  • bad breath
  • an unpleasant taste in your mouth

Seeing a dentist

Visit your dentist regularly so early tooth decay can be treated as soon as possible and the prevention of further decay can begin.

Tooth decay is much easier and cheaper to treat in its early stages.

Dentists can usually identify tooth decay and further problems with a simple examination or X-ray.

Find your nearest dentist

It’s also important to have regular dental check-ups.

Adults should have a check-up at least once every 2 years, and children under the age of 18 should have a check-up at least once a year.

Treatments for tooth decay

Early-stage tooth decay

Early-stage tooth decay, which is before a hole (or cavity) has formed in the tooth, can be reversed by:

  • reducing how much and how frequently you have sugary foods and drinks
  • brushing your teeth at least twice a day with fluoride toothpaste

Your dentist may apply a fluoride gel or fluoride paste to the affected tooth.

Fluoride helps to protect teeth by strengthening the enamel, making teeth more resistant to the acids from plaque that can cause tooth decay.

Treatments for holes in teeth

When there’s a hole in the tooth, treatment may include:

  • a filling or crown – this involves removing the dental decay and filling the hole or covering the tooth (read about what NHS fillings and crowns are made of)
  • root canal treatment – this may be needed to remove tooth decay that’s spread to the centre of the tooth where the blood and nerves are (the pulp)
  • removing all or part of the tooth – this is usually advised when the tooth is badly damaged and cannot be restored; your dentist may be able to replace the tooth with a partial denture, bridge or implant

Preventing tooth decay in adults

Although tooth decay is a common problem, it’s often entirely preventable.

The best way to avoid tooth decay and keep your gums as healthy as possible is to:

  • visit your dentist regularly – your dentist will decide how often they need to see you based on the condition of your mouth, teeth and gums
  • cut down on sugary and starchy food and drinks, particularly between meals or within an hour of going to bed – some medicines can also contain sugar, so it’s best to look for sugar-free alternatives where possible
  • look after your teeth and gums – brush your teeth properly with a fluoride toothpaste twice a day, and use floss and an interdental brush at least once a day
  • see your dentist or a GP if you have a persistently dry mouth – this may be caused by certain medicines, treatments or medical conditions

Protecting your child’s teeth

Establishing good eating habits by limiting sugary snacks and drinks can help your child avoid tooth decay.

Regular visits to the dentist at an early age should also be encouraged.

It’s important to teach your child how to clean their teeth properly and regularly. Your dentist can show you how to do this.

Younger children should use a children’s toothpaste, but make sure to read the label about how to use it.

Children should still brush their teeth twice a day, especially before bedtime.

What causes tooth decay

Your mouth is full of bacteria that form a film over the teeth called dental plaque.

When you consume food and drink high in carbohydrates, particularly sugary foods and drinks, the bacteria in plaque turn the carbohydrates into energy they need, producing acid at the same time.

The acid can break down the surface of your tooth, causing holes known as cavities.

Once cavities have formed in the enamel, the plaque and bacteria can reach the dentine, the softer bone-like material underneath the enamel.

As the dentine is softer than the enamel, the process of tooth decay speeds up.

Without treatment, bacteria will enter the pulp, the soft centre of the tooth that contains nerves and blood vessels.

At this stage, your nerves will be exposed to bacteria, usually making your tooth painful.

The bacteria can cause a dental abscess in the pulp and the infection could spread into the bone, causing another type of abscess.


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