Human teeth have stories to tell about the lives our human ancestors led. Studying ancient teeth reveals life history, growth, and diet of primates and our human ancestors, as well as the relationships between different species.
What will anthropologists of the far future learn about us when they examine our fossilized teeth? Debbie Guatelli-Steinberg, a professor of anthropology at The Ohio State University, already has a pretty good idea about what her future colleagues will find when they examine our teeth. And she’s written a book about it: “What Teeth Reveal About Human Evolution” (Cambridge University Press, 2016).
Ask her about today’s teeth and she’ll tell you to be thankful for modern dentistry. Our teeth are living unnatural lives, and if it wasn’t for skilled dentists many of us would probably be experiencing serious health problems.
In the book, she noted that 99 percent of humans’ evolutionary history was spent eating foods that were hunted or gathered. Our current diets of soft, processed and sugary foods are nothing like the diets for which our teeth are adapted.
“Problems like cavities and plaque buildup have been magnified tremendously in humans today,” she said. “Natural selection has not prepared us well for the kinds of food we eat today.”
In addition to having much higher rates of cavities and plaque, modern humans are much more likely to have misaligned teeth that require orthodontic treatment or surgery.
“Soft diets do not stimulate jaw growth, and teeth, especially our third molars (wisdom teeth), become impacted,” she said. Impacted wisdom teeth are a relatively modern problem, becoming 10 times more common after the industrial revolution than previously.
Learning From Teeth
Teeth are the most common skeletal remains found in fossils. That’s because they are small and very mineralized, making them resistant to decomposition and able to maintain their original qualities.
Teeth also contain a record of a lot of aspects of their own development. Like the rings in tree trunks, there are microscopic lines – called perikymata – on the outside of teeth that mark the incremental growth of enamel on a young tooth. Researchers can use perikymata to gauge how long it took for the tooth to mature. And that gives them an indication of the length of an individual’s childhood. The amount of wear on fossilized teeth also provides a very rough estimate of how old an adult was when he or she died.
Microscopic wear on the chewing surfaces of teeth can also suggest what kind of food an individual ate. Chewing different kinds of foods creates different wear patterns. Scientists can identify chemicals and trace elements found in fossilized teeth to determine an individual’s diet.
Teeth can also fill in some gaps in the historical record, or confirm historians’ theories For example, tooth growth is disrupted in periods of severe physical stress, such as illness or starvation, so teeth can be a window to challenges that our ancestors faced, Guatelli-Steinberg said.
And, as noted in an article in Scientific American, “Teeth are tools. We use them for chewing to facilitate consumption, but we also use them to tear things or hold things. We do these things today, so our ancestors probably did them too. This has nothing to do with evolutionary theory and everything to do with practicality. We see this behavior in different animals as well. These types of activities may leave traces behind, and be recorded in the health of dental remnants we recover.”
In her recent lab work, Guatelli-Steinberg has used a relatively new method of studying fossilized teeth to examine growth increments. The technique pioneered by anthropologist Tanya Smith, called X-ray synchrotron microtomography, uses a specialized imaging machine to see inside teeth without having to cut them up.
This allows researchers to create virtual sections of fossil teeth to see periods of growth, or when growth was interrupted, in increments as short as just a few days, she said.
Regardless of what new techniques are developed to study teeth, Guatelli-Steinberg said she expects future anthropologists will “likely have a field day” studying modern human teeth.
“In various cultures today, we have people who notch teeth, inlay them with jewels or gold, lengthen them, file them down and remove them altogether,” she said. “One can only imagine what anthropologists will make of all the things we do to our teeth today.”