NPR has a story on dietary analysis of fossilized hominin teeth called Dental Detectives. Erin Ross writes:
When scientists want to know what our ancient ancestors ate, they can look at a few things: fossilized animal bones with marks from tools used to butcher and cut them; fossilized poop; and teeth. 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.
“They preserve really well,” explains Debbie Guatelli-Steinberg, a dental anthropologist at Ohio State University. “It's kind of convenient because teeth hold so much information.”
The structure of a tooth and even the amount of enamel, for example, hint at what the teeth are adapted to eat.
Peter Ungar, of the University of Arkansas, adds this:
“If you eat Jell-O almost every day of the year, but sometimes you need to eat rocks … you want teeth that can eat rocks,” he explains. So, teeth are usually adapted for the toughest component of an animal's diet, not what it eats on a daily basis.
To see what an animal was actually eating, Ungar studies something called dental microwear, the marks left behind by food on teeth. 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.
Beyond this, though, detailed isotope analysis of teeth has revealed changes in migration and patterns: Ross writes:
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.
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.
More pieces to the puzzle. Read the whole thing.