The Gap
Where
Something
Happens

Why is it important to learn more about the belly button and its biodiversity?

The belly button is a patch of skin that happens to be more intriguing than most patches because it is unusual. The microbes on our skin help to protect us from pathogens. They create most of our bodily aromas (good and bad). And they, more generally, play a key role in keeping our immune systems working in proper order. As a result, we study the belly button as a sample of the skin microbiome which is as important to our well-being as most of our organs.

“The belly button is one of the habitats closest to us, and yet it remains relatively unexplored.”

Why do you think this is?

It is hard to see. I mean this in two ways. First, well, the belly button is not very conspicuous in our daily lives. But second, the life in our belly button is microscopic life. It is hard to imagine that we are covered in such life. It is out of sight, out of mind. Also, as humans we tend to think of ourselves as going alone in the world. The idea that we are in a constant dialogue with species that are on and in us that are as much a part of us as our own cells, it is foreign to our philosophies.

I noticed that many of the authors involved in this research have a background in forestry, plant sciences, biology and environmental science. You yourself have compared the belly buttons to rainforests. How did you all collect around the navel?

We were studying the life on ambrosia beetles (which carry fungi in little “pockets” on their bodies; they plant the fungi on dead trees and then farm it for their babies). It occurred to us at that time that we seemed to know more about the life in the divots of obscure beetles than the life in our own divots and dimples. And so we began to poke around.

You speak of desert-like conditions on the human skin, of “dry” and of “wet” areas. Is the navel such a wet area? Could we perhaps look at it as an oasis?

Yes, the navel is a kind of oasis for species that like wet places with little oxygen, especially the navels of relatively big folks whose navels offer more and deeper habitat.

You describe the belly button as an environment that varies little from person to person in terms of morphology. It is protected from daily washing and as such has the potential to host a less disturbed bacterial community. Would you say that a belly button functions as a little incubator of its own?

The entire skin is an incubator in a way, wherein species are fed by apocrine glands and live in between the sheltering flakes of skin. Though the metaphor breaks down a little because it is an incubator amidst relatively harsh conditions.

On average, how many life forms do I share my belly button with?

100

Do you think the biodiversity of a belly-button can tell us something about the individual it belongs to? For instance in the research, you mention two types of phylotypes from an individual who self-reported not having showered or bathed for several years (these were two of three phylotypes of Archaea, a domain of life found in extreme environments and not previously reported from human skin). How much control do we have over the environment that is our body?

As of now, we think that the microbes in belly buttons tell us something about 1) how often people spend time out amongst wild plants and their microbes, 2) whether people use antiperspirant and 3) which version of the gene they have that determines how much microbe food their apocrine glands produce.

You have sampled over five hundred volunteers. Were these all random, or were some of them related? Do genetics play a part in the belly button biodiversity of an individual? For instance, if the umbilical cord once attached to my navel had been attached to a different mother, could this have an effect on the current biodiversity of my navel?

Yes, genetics plays a big role. It explains about thirty to forty percent of who lives on your skin in general and in your belly button in particular. The process of birth is also important too. Whether you were born c-section or vaginally likely influences which strains of bacteria you have (and whether they are the same strains your mother has), though this has been better study for gut microbes than for skin.

The Belly Button Biodiversity project has conducted a nation-wide research. Have you been able to find local differences? For instance, could we find different forms of life in my belly-button here in Amsterdam, than in yours in North-Carolina?

Not much so far.

In your results, you frequently compare your findings on the belly button with those on tropical rainforests or estuarine fish. Why is it these specifically that make for an apt analogy?

In part, we just understand rain forests better than we understand human skin (and belly buttons in particular) and so it is useful to compare to what we better understand. But, more specifically, skin microbes tend to be really diverse but dominated by a small handful of genera and species; this is a lot like rain forests where one can find many many tree species and yet a small handful of tree species are widespread and common (and have much bigger effects).

French psychoanalyst Jacques Lacan once referred to the navel (in reference to Freud’s concept of “the navel of the dream” - the point where it becomes impossible to analyze a dream) as “a gap where something happens.” Do you think this is applicable in your research as well?

Metaphorically, yes. The navel is where we were connected to our mothers. But we are also connected to our mothers by the microbes they have given us, microbes including those in our navels. The gap in this case is the gap the microbes feel, their populations having become separated when we became separated from other mothers and then, once separated, evolving along their own unique trajectories.

Do you think the belly button is a peaceful habitat, or is there a battle for survival going on in my navel?

Always a little of both.

What, to you, is the navel of the world?

The rain forest.