Dr Brenna Hassett
Dr Brenna Hassett is a dental anthropologist and bioarchaeologist. After working on dig sites across the world, she is now working on post doc research at the Natural History Museum in London determining childhood experiences from the examination of teeth. Her focuses include searching for archaeological evidence during the transition from agriculture to sedentism in SE Asia and the transition to urban life in early modern London. She is also one quarter of the Trowelblazers team.
It’s taken 15,000 years but your face is slowly shrinking
On becoming a dental anthropologist
Ah, well, you start off in either archaeology or dentistry and you head towards the other one until you meet somewhere in the middle. So I could describe myself variously as an archaeologist who pretty much focuses on teeth or someone who digs up dead people. Both of those kind of get you a weird reaction depending on who you tell.
I was never going to be a dentist. I started off in archaeology and I thought…I looked around and I looked at…I went on, sort of, my first couple of excavations and it’s all amazing because, you know, you’re 18 and in Greece, you’re in Turkey, you’re in Egypt; I worked at the Pyramids, you know, you look out your window and there’s the Pyramids and you’re digging them, pretty cool. And then I look around and everyone else is basically coming in and they’re complaining about their knees and they’re complaining, ‘Oh my back hurts’, or it’s the shovel and the guys who seemed like they were really getting stuff done, who really had, you know, interesting stories to tell were the guys who were looking at the skeletons, who were looking at the human remains. You can dig up an entire city and you can talk about walls and, you know, the type of people, ‘Oh it looks like craftsmen lived in this area’ but you don’t talk about individuals. If you talking about a tooth, though, that belongs to an individual. You’re talking about their childhood. And it’s one of the only ways you can kind of get back to an individual in archaeology. If history is written by, you know, kings and old men then this is one of the ways that I can look at, say, a kid who died when they were 13 years old 10,000 years ago, and I thought that was pretty cool.
I think I’ve ended up in dental anthropology because humans are kind of interesting. Humans have a long history of doing fascinating, strange things. It turns out that we don’t actually know much about how we got to be how we are. So one of my big focuses is on how we got into this farming thing. This fascinating, cool new technology we came up with 15,000 years ago. Didn’t really need it before, but it’s massively changed the way we live, the way we eat, even the way our faces are shaped, the way we use our teeth. We’re kind of driving our own evolution by the way we keep inventing new things. So archaeology is a way of looking at that, and dental anthropology is way of kind of getting individual histories. So I can look at your teeth and each little tooth has a secret record of your growth from the time it was growing.
So I could take your tooth, pop it in a saw, slice it down the middle, grind it up, look at it under a microscope and I could give you a day by day account of your growth as a child and that’s kind of a cool way to access the past. Nothing else can really do that. We don’t have books written about the people who sort of went, ‘Hey, I’m gonna stop hunting big game animals and I’m gonna hang out right here and grow some stuff’. So this is kind of the only way we have to access that kind of information. I thought that was cool.
On using teeth to tell history
Your teeth have all the sort of evil secrets of your childhood. So your teeth are formed up of a bunch of chemicals. Those chemicals are locked in there by, you know…they represent the water you were drinking, the geology you were hanging out in when you were growing those teeth, so we could look at, say, the different types of oxygen in your teeth and we could map that out and say, ‘OK, well this person’s getting oxygen and it’s from lower down. It’s from lower down in the water cycle. So it’s from near the beach. This person’s got a different kind of oxygen and it’s from water that’s actually higher up in the water cycle so it’s probably coming off a mountain.’ And we could do that to your teeth. We could do that to an animal’s teeth and we can start mapping the movements of people as they wander through the world.
The other thing we can look at, which I’m really interested in, is the horrible things that go wrong in your childhood and the records of those. It turns out that your teeth grow a little bit like an onion or something like that. Imagine a bunch of layers. Sometimes something happens to the growing organism that’s basically so bad that everyone basically goes, ‘Ah! Systems down, systems down!’ All growth stops and you can see in the tooth this permanent record of where growth kind of paused, and it shows us a little line across your tooth and that’s called an enamel Hypoplasia, which you don’t ever need to know, but that record shows us when something bad happens to you. We don’t necessarily know what it was, it could’ve been a fever, a disease, malnutrition, something like that. They did some terrible experiments with beagles where they locked them in a dark room. Apparently that is not good for you. Don’t do that. Don’t do it to beagles either. But you can actually start mapping out these records, so one of my projects is in Turkey and I’m looking at a site where everyone was really into the hunting thing, they all kind of settled into this village. All of a sudden they’re surrounded by, you know…they’re living right next to their animals, that’s a good way to introduce a lot of diseases, um, and people are probably having more children, population’s growing, they’ve got more food, they’ve got all these nice, high calorie carbs – carbs were a problem then too – ah, so I can have a look at the records of their growth and kind of say, ‘OK, well, you guys who were before farming, you know, do you have a lot more of these lines on your teeth or do we get the lines on the teeth after farming?’ And what we generally find is that these records of health disruptions, these sort of insults to the poor little kids, they happen a lot more frequently after we developed farming than before.
On the golden age of teeth
You’re about 100,000 years too late for good teeth. Peak teeth has passed, tragically. One of the weird things we’re doing is, ah, we’re slowly developing smaller faces. Your face is shrinking. It’s taken 15,000 years but your face is slowly shrinking. You’re familiar with wisdom teeth? So, wisdom teeth are these horrible, nasty things that go wrong for everybody. Everybody sort of gets an impacted one and you have to have horrible surgery to sort of crack it out of your jaw. It’s terrible. Wisdom teeth used to fit in our mouth. If you look at the skeleton of a nice, I dunno, Anglo-Saxon dead person from Abingdon or something, one of these nice 13th century British skeletal samples, you look at their mouth, they have a beautiful uncrowded row of teeth. Quite nice. You could look at someone who’s even earlier and they’d have a less crowded row. So someone who, for instance, wasn’t chewing soft bread but was instead having more of a hunter gatherer life, you very rarely see these sort of higgledy piggledy teeth. And what we get with the third molar, because it comes in last, there is no room at the inn. We have tons of problems because our faces are slightly smaller. It’s not sure of what’s driving what in terms of evolution, but increasing numbers of human beings are born without third molars. They don’t even get them. So you might’ve had relatives or, you know, evil lucky friends who just go, ‘Oh, I didn’t have third molars’ which is increasingly the case. So we’re actually losing a tooth. We’re in the process of, you know, shrinking our faces, our third molar doesn’t fit and, ah, we’re changing the way we look and it’s basically happened in the last 15,000 years.
On recent research
One of the most recent things I’ve done is worked on a site called A??kl? Höyük in Cappadocia which is a beautiful, beautiful site and it sort of comes into being around 10,000 years ago. This is really…in that region of central Turkey, that’s when they first sort of get the farming idea. And the funny thing is they sort of start living in a settled city, so it’s a very early city, one of the first cities in the world and they start living there but they’re still hunting big animals. So they’re living in the city but they’re not farming yet. Slowly, over the course of about a thousand years, they start farming. So my interest in going and working at this site is to look at the teeth and look at the kids and say, ‘Well what is it like to be a kid 10,000 years ago when we come up with, well, basically one of the most interesting experiments we’ve run on ourselves. So my work has been looking at the lines on teeth, in the kids, and what we’ve seen is it looks like the earlier kids have lines a little bit further apart and the later kids who are living in a city basically – or a dense settlement, it’s not a city like you’d recognise today, but relying on agriculture – they have lines closer together. Lines that appear about every two years.
And every two years is a weird time; it’s not like every year, which would be like, maybe you have an epidemic or something comes round, you know, summer sickness or something. It’s not kind of every couple of months, but it’s every two years. And what happens every two years? We think, possibly, this is related to every two years, a sibling is born.
So this is telling us about population expansion and how we got into cities and then suddenly every two years, maybe there’s another sibling. We know from looking at hunter-gatherers who aren’t living together, depending on farming, they’re having kids maybe every four or five years because that’s what they can afford. That’s what will survive. And if we get together and we’re living in these dense populations, relying on, I guess, hopefully, you know, more calories…you know, we’re growing our population. So, hopefully, we might be seeing evidence of that or it could be something different totally because it’s science and I’ll be proven wrong.
On teeth aging
It’s a little bit like horses. You know the phrase, ‘Don’t look a gift horse in the mouth?’ It’s because horses…their teeth wear down and they constantly wear, wear, wear and once a horse runs out of teeth, the horse runs out of life. They can’t eat anymore, they die. However we have this amazing thing called, you know, culture and brains, we’ve discovered other things to do besides wear our teeth down. We can actually still keep on eating. Plus we mostly eat things like Pot Noodle now so it doesn’t really affect us as much.