Austria of 12.5 million years ago seems to have been a very hospitable home for Dryopithecus carinthiacus. The forested landscape treated the now extinct ape, which measured roughly four feet in length and resembled a mix between a monkey and a chimpanzee, to a veritable feast of fruits. For nine to ten months out of the year, Dryopithecus could gorge on early forms of plums, cherries, grapes, mulberries, strawberries, and various citrus fruits. But eating all of those sugar-rich fruits may have come with a downside of which modern humans are quite aware: tooth decay.

Dryopithecus fontani, from Late Miocene of Eurasia.

In new study published in PLoS ONE, German researchers Jochen Fuss, Gregor Uhlig, and Madelaine Böhme revealed the earliest known cavity in hominids, a group which includes modern humans, human ancestors, and many apes. A 12.5 million-year-old Dryopithecus dubbed LMK-Pal 5508 found near St. Stefan, Austria had deep lesions in its left molars that likely required several years to form (see picture at top). Moreover, signs of wear observed on the right tooth row indicated that the individual likely experienced a painful toothache, the researchers speculated.

While cavities are well known to modern humans, they are quite rare in our ape relatives. Cavities occur in just 1.38% of the permanent teeth of wild chimpanzees, the researchers reported. According to the National Institute of Dental and Craniofacial Research, 92% of American adults aged 20-64 have had a cavity.

The reason for the disparity should be quite obvious: sugar. Bacteria in your mouth convert sugars into organic acids which demineralize and dissolve the enamel and dentine that makes up your teeth. The more sugar you eat, the more acidic your mouth becomes, the more your teeth decay.

Most wild apes don't regularly consume candy, soda, ice cream, or the plethora of other sugar-laden foods available at any grocery or convenience store, but it seems that Dryopithecus did, in a manner of speaking. Living in its fruit-rich forest, the early ape was like a kid in a candy store. The sugar buffet may have been particularly bountiful in late autumn, allowing Dryopithecus to binge and build up fat stores for the winter. The researchers speculate that this situation, which may have played out with other apes across Eurasia millions of years ago, prompted hominids to lose an enzyme called uricase. Uricase breaks down uric acid, so organisms without uricase will have more of the acid. Uric acid blocks fatty acids from degrading, allowing hominids to accumulate fat stores from simple sugars much more quickly, and thus store energy for times of scarcity.

Turns out you can learn a lot from a 12.5 million-year-old cavity. Tell your dentist!

Source: Fuss J, Uhlig G, Böhme M (2018) Earliest evidence of caries lesion in hominids reveal sugar-rich diet for a Middle Miocene dryopithecine from Europe. PLoS ONE 13(8): e0203307. https://doi.org/10.1371/journal.pone.0203307