Learning human history from the dirty teeth of the dead

Your dentist reminds you to brush your teeth. She tells you that you should floss more. She says that sugary drinks are bad for your teeth. What you dentist probably doesn’t mention is that by cleaning your teeth, you’re possibly removing a record of your life that could help preserve a (slightly gross) slice of your biography for long after your eventual death.

Preserved in plaque

The plaque that develops on our teeth can actually harden and act as a sort of fossil record of what your mouth was doing when you were alive. Anthropologists have started looking at plaque found in skeletons’ mouths for samples of plants, bacteria, meat and even textile fibers. Beyond foreign debris, they’ve also been able to find out more about the genes of the person from their accumulated plaque than is often possible with the actual teeth.

Oral plaque is actually so robust that it’s being used as a source of DNA, holding 100 to 1000 times more nucleic acids per milligram than other available sources. This has allowed scientists to sequence genomes that weren’t in environments that would naturally preserve tissue, like permafrost. So far the oldest dental buildup to yield DNA has been 10,000 years old, and there’s hope that dirty mouths will make a wider set of samples useful for genetic studies.

Anthropology through oral history

The details trapped in plaque have been helping anthropologists in a number of different studies. By tracing beta-lactoglobulin protein in plaque from different human populations, we’re getting a better understanding of how lactose tolerance arose in humans. So far the oldest confirmed samples were from Bronze Age teeth, but Neolithic skulls may yield even older secrets. Other investigations closer to a dentist’s heart have looked at the evolution of periodontitis, a gum disease that affects many people today.

Source: Meet the Dentist to the Dead by Megan Gannon, Scientific American