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The Remarkable Biodiversity Of Belly Buttons


Our fascination with the belly button fades after a certain age, maybe eight years old. But after some serious navel gazing, researchers have reignited interest. It turns out that like our fingerprints, retinal patterns and our DNA, our belly buttons may be unique because of the mix of bacteria found therein. Rob Dunn is a science writer and a biologist at North Carolina State University where he works with the Belly Button Biodiversity Project. He's also the author of "The Wild Life of Our Bodies" and joins us now by phone from the Nature Research Center in Raleigh. Good of you to be with us today.

ROB DUNN: Oh, thanks for having me. It's a delight.

CONAN: And I - your website says you approach navels like an explorer approaches a new world.

DUNN: Well, so I started my career working in tropical forests and one of the things I realized, sort of midway through is that there is all kinds of stuff in our daily lives that we understood almost nothing about and it was far cheaper to go find belly buttons than it was to get to far-away rainforests. And they've proven to be equally interesting.

CONAN: Biodiversity, we keep hearing about it in the rainforest.

DUNN: Yeah. And we have it on our scan in our houses and even on our belly buttons too. And so the average belly button, we're finding tens of species of bacteria and other organisms. And across a group of people, we find thousands of kinds of bacteria living in belly buttons, and also all over the skin more generally.

CONAN: And I gather some rather exotic types of bacteria.

DUNN: We do. So I mean, one of the interesting things about our skin is that we treat our skin in a very different way today than we would have a hundred years ago or a thousand years ago. And so, there's the potential for us to have changed what lives on us pretty dramatically.

And one of the fun things in this study so far is we had one individual who claimed to have never washed, and that he had many, many bacteria species in his belly button. But he also had an entirely different lineage of life called the Archeans that we usually think of as being in deep sea vents and other sort of far away realms. But it turns out they also live in belly buttons, and we're looking at armpits now too. We actually found some of these in armpits as well. And so...

CONAN: I hesitate to say those could be extreme environments too.

DUNN: The nice thing about working with the public is we can get people to sample their own parts. They don't pay us well enough to sample other people's armpits, I think.

CONAN: Well, as you suggest, a lot of us have changed hygienic habits over the past couple of centuries, in particular. Belly buttons though, don't seem to get cleaned as thoroughly is what you're saying.

DUNN: Yeah. I mean, they're kind of a nature reserve when it comes to our body. And so I think that the better indication of, you know, what our body is like in terms of microbes and those places we don't scrub all the time. You know, our hands are covered with lots of species, but those include both the things that are good at dealing with soap and the things we've just encountered, whereas, the belly button is kind of a little bit more unreserved. We very rarely shake belly buttons with people that we often shake hands. It makes a difference.


CONAN: I could understand that. So as you explore the life of the belly button, one of the things, of course, that it points out is we think of bacteria and react in horror. Of course, we can't live without them. They are our partners in life.

DUNN: Yeah, that's right. So, if you really scraped all of the life off of your skin, all of the bacteria and Archaea and nematodes and everything else, you would almost certainly die from pathogens. Your bacteria are your first line of defense. And they also do all sorts of other things. And so all of the smells you attribute to other people, those are almost exclusively microbial. And so that includes the bad smells but also the good smells.

And so the line between us and them is very fuzzy, but we don't really understand it very much about, you know, why you have a specific set of microbes in your belly button and I have another set, and how we might alter that trajectory so as to produce, you know, sets of belly button bacteria that are more beneficial or smell nicer or whatever else. And the first stage is really just figuring out who's there. And so it's kind of like Lewis and Clark work, you know, without all the hazards.

CONAN: We're talking with Rob Dunn; is a biologist and writer for the Department of Biology in North Carolina State University where he works at the Belly Button Biodiversity Project. You're listening to TALK OF THE NATION from NPR News.

And how do people react when you tell them you work for the Belly Button Biodiversity Project?

DUNN: Well, I think it's a mix. So we try to make all of our work as public as possible. And so, for example, you can go to our website and you can find all of the data we have so far. And you can actually contribute or own hypothesis as to what explain differences from one person to the next.

And so we get a lot of interest that they engage to people who want to help us with the mysteries that are emerging with these microbes. We also get lots of teachers who are - who want to be involved, and then we get a fair number of emails with people sending us pictures we probably don't really want to see if their husband or wife's belly button and something that's growing in it. So it's mixed response I guess.


CONAN: I suspect that's a good way to put it. There was a fascinating finding in one of your subjects, someone who had bacterium that had previously only been found in soil in Japan, and he had never been to Japan.

DUNN: Yeah. I mean, it's one of the amazing things is that we know so little about the microbes that are all around us. Often we'll find something that can actually be quite common on someone. And it's the first time we've have really seen it or has only seen it in really extreme places. And so - then we just have those two data points, and so it's hard to know what to make of that.

And as another example, one of the samples from me, I had microbes that tend to be associated with pesticides. And so it's hard to know just from that one sample what does that mean? But it invites more study, so that, you know, whether I bumped into a plant that was covered in pesticides? It's some daily thing, you know, I'm doing, exposing me to more than I would like?

And, you know, it's all the questions we would ask of - about a forest, we can ask about our own bodies, we can ask about our homes. And so as a scientist, it's actually a really exciting time to be able to go into these habitats. I think medically, as a human - and this is why we get the emails - it's also really frustrating if you then have a problem that emerges from having, you know, not the right kinds of bacteria on your body or a pathogen or not enough species if you feel desperate enough to send a scientist the picture of your belly button.

CONAN: Well, in the rainforest you expect to a find a species, beetles previously unknown to science. Are you finding bacteria previously unknown to science?

DUNN: Yes. So the way we study these bacteria is by looking at their genes. And many of the, sort of, letters of these genes that we see, no ones ever seen before. And so we're finding not only whole new species in belly buttons but whole new lineages. And so then the study of those lineages begins, sort of, from stage one. You know, they don't have names even their families often don't have names. And so it's really a pretty amazing time. I think it's very easy to imagine that we understand most of what's living around us.

But the truth is if, you know, when you're in your house or your studio, in that house or studio with you are thousands, maybe tens of thousands of species, most of which no ones ever, every studied.

CONAN: I wonder, some people - there is now a class people who go into belly buttons as a daily practice, laparoscopic surgeons. Have you spoken with them about what they find in people's belly buttons?

DUNN: So I've received a few emails but we haven't actually sampled any laparoscopic - well, we don' know if we've sampled any belly buttons that have had laparoscopic surgery. We probably actually have. But we do hear lots of anecdotes about belly buttons that we didn't know before.

For example, it turns out that in Japan, traditionally, mothers tell their children to never wash their belly button or they'll get a stomach ache, which is actually an interesting sort of metaphorical concepts for some of what we're thinking about in terms of health of microbes and your skin. You know, we would urge people not to be so hyper clean in their lives that they both get rid of the bad bacteria and the good ones. And so Japanese mothers seem to have known quite a bit.

CONAN: I suspect that's true, and I suspect they're not shy about telling their children about it either.

DUNN: That seems to be the case.

CONAN: Thanks very much for being with us today.

DUNN: Thank you so much, Neal. Keep an eye on your belly button.

CONAN: Rob Dunn is a science writer, a biologist in the Department of Biology at North Carolina State University. He joined us today from Raleigh. Tomorrow, traffic. L.A.'s is legendary, they're trying something new. They have synchronized every traffic light in the city. Join us for an update with Tom Vanderbilt tomorrow right after I go home and take a shower. It's the TALK OF THE NATION from NPR News. I'm Neal Conan in Washington. Transcript provided by NPR, Copyright NPR.