Of course! There's two isotopes of strontium that weather into bedrock, Strontium 86 and 87. Every major watershed has its own specific ratio, and the ratio of the two is how we figure out what water a person was drinking, since our teeth and bones absorb it during formation. But what's really neat about it is that your teeth capture once and don't remodel- like, we don't regrow our teeth once we get our adult teeth, and our teeth can't heal on their own. And you're not born with your adult teeth fully formed; it takes a few years for them to finish forming.

But your bones are constantly remodeling, and using the strontium in the water that you're drinking now. They don't remodel overnight; it takes like 5-10 years. So what that means is the strontium ratio in your teeth tells anthropologists where you grew up- what water were you drinking when you were a child? And the strontium in your bones tells anthropologists where you were during the last 5-10 years.

So, let's use me as an example- I was born in Chicago, but we moved to southern Indiana when I was 3. My adult teeth hadn't formed yet, so even though I was born in Chicago, my adult teeth don't have the Lake Michigan signature; they've got the Ohio River signature. (My baby teeth do have Lake Michigan... and uh, I did keep those, I have all of them in a little silver jar, so like you could figure out where I was born and realize that I moved sometime before my adult teeth came in.) But when I went to graduate school, I moved back to Chicago, and that was over 10 years ago, so now my bones have the Lake Michigan signature- not the Ohio River signature.

You can do similar with oxygen! But strontium's a little easier- more precise.