Dental Detectives
Teeth are providing a richer picture of who we are and how we came to be
What can scientists look for when they want to know what our ancient ancestors ate?
a. fossilized animal bones with marks from tools used to butcher and cut them?
b. fossilized poop?
The first two can tell us a lot, but they're hard to come by in the fossil record. Thankfully, there are a lot of 'teeth' to fill in the gaps
Microscopic Scratches on the Teeth!
Teeth are the hardest part of the skeleton but the particles in foods are still capable of leaving scratches and other marks on the surfaces of teeth. Different types of food will leave different kinds of marks. As we chew on say, a celery stick, hard particles — either bits of silica from the plants' cells or sand and grit from the surrounding environment — are dragged across and pressed into our teeth. When our ancestors ate tough grasses by moving our teeth side-to-side, the teeth got tiny, microscopic scratches.
Scientists compare the marks left on fossil teeth with those found on the teeth of modern-day animals to reconstruct the prehistoric diets of our ancestors. Harder foods, such as nuts, seeds, tough fruits and tubers tend to leave small pit marks in the enamel that covers the tooth surface, whereas softer leaves and fruits leave many small scratches.
Peter Ungar, an anthropologist calls it a "foodprint".
Studying the molecules that accumulate in teeth from the food we eat
So we can tell what an animal was adapted to eat and what it ate shortly before it died. But how do we know what it ate for longer periods?
Scientists have to look deeper — to just below the surface of a tooth — for certain molecular signatures left behind from daily meals.
As our teeth grow in early childhood and adolescence, they incorporate certain molecules from the food we eat. The same was true for our ancestors. Paleoanthropologists studying ancient diets are especially interested in carbon molecules in our ancestors' teeth, because they come from plants and stick around for a long time.
Data from isotopes confirmed that Lucy's species switched from forest foods to savanna foods about 3.5 million years ago
That transition from forests to grasslands may have played a key role in human evolution, explains Matt Sponheimer, a paleoanthropologist at the University of Colorado, Boulder. Some researchers even think that adding more grass to our diets gave our ancestors more foods to eat and places to live as the early climate changed causing Africa's forests to shrink
Nitrogen and Vegetarianism
Teeth from more recent fossils reveal more because they have more isotopes preserved in them. For example, the nitrogen in the teeth of Neanderthals can reveal whether the protein they ate came from plants or animals. It's one of many reasons researchers think Neanderthals hunted large mammals, though scientists have also found fossilized plants stuck in Neanderthal teeth.
Barium in teeth and baby weaning
Researchers were even able to use isotopes to find out when one Neanderthal started weaning her baby. As teeth grow, they lay down layers of enamel. And barium, a molecule children get from breast feeding mothers, builds up in baby teeth until the mother stops nursing. By comparing barium in a Neanderthal tooth with levels in donated present day baby teeth, the scientists were able to find out that the Neanderthal baby had been weaned at about seven months.
Strontium in Wisdom teeth and Migration
We can even use teeth to tell if someone moved between places with dramatically different foods or soils. Since wisdom teeth are the last adult teeth to come in, comparing them to an early emerging canine tooth can give scientists a dietary snapshot across time. Say someone was born in Africa and moved to a new continent as a preteen, while wisdom teeth were still growing. A comparison of the isotopes in the teeth would reveal the story of that migration. This is done by measuring strontium and oxygen proportions and matching them to the strontium in the rocks of that area