The World in Your Belly Button


In Dr. Seuss’s literary classic, “Horton Hears a Who,” an elephant discovers an entire society of tiny people living on a small flower.

In the last 30 years, there’s been an explosion of interest in something nearly as fantastical as a Dr. Seuss book: the human microbiome, or the community of bacteria living on and in the human body (which outnumber your three trillion cells ten to one). We’re only beginning to learn how the human microbiome affects our health, but what we know so far is revolutionary.

Obesity, mental health, neurological disorders, immune function and more have been linked to the microbiome (check out this article on the gut microbiota for some more details on that). Inventions in the last two hundred years have hugely changed how our bacteria coexist with us (think antibacterial soap, antibiotics, sterilization, and ubiquitous hand sanitizer dispensers that kill 99.9 percent of bacteria). Because of this, many bacteria are living in conditions in which they have not adapted to live, which may be leading to the health conditions mentioned above. One of the last areas on the human body that isn’t often subject to these modern technologies, (read: that the average person still forgets to wash) is the belly button.[1]


picture2Toe Culture by Kim F is licensed under CC 2.0

The Dunn Lab at UNC studies the belly button microbiota through their Belly Button Biodiversity project.[2] Here’s how it works: people swab their belly buttons and give the samples to the lab, where they are grown on petri plates and ‘sequenced.’ Sequencing is a process that allows scientists to identify bacteria by recording their genetic codes. In this case, the Dunn Lab uses the 16S gene as a fingerprint to identify bacterial species rather than having to find the entirety of every bacterial genome. This allows scientists to identify the types of bacteria present inside a given person’s belly button.[3]


This general procedure is pretty standard, but the results surprised even the scientists eccentric enough to come up with this idea.

In the first 60 belly buttons the researchers tested, they found 2,368 unique bacterial species, 1,458 of which had never been identified before. Most of the bacteria in a single belly button are of just a few common types, and these same types of bacteria are present in large numbers in most belly buttons. Despite this, the researchers didn’t find a single bacteria that all sixty people had. Even stranger were the bacteria there were few of: more than 90% of the bacteria found were present in only 10% of the belly buttons, and many of the bacteria were unique to just one person. Each person’s belly button microbial community is so unique that it can be used to identify that person as accurately as their fingerprint could.[4]

And the results of this experiment only get weirder. What species were these unique bacteria? Ignoring the fact that about 1500 of them had never been seen by scientists before, the ones the researchers were able to identify brought up just as many questions:

Why did someone have bacteria that normally thrive at the bottom of the ocean in sulfur vents or in the arctic on ice caps?

Why can identical twins who grew up together have such radically different bacteria in their belly buttons?

Why did a man who had never been to Japan have bacteria that otherwise only live in Japanese soil?


We still don’t know. The researchers have looked into factors like age, sex, ethnicity, geography, belly button type, and frequency of washing, and they haven’t found any connections between the types of bacteria present and any of these other factors.[5]

So now what? Unhappy with the fact that the average person has cripplingly poor access to scientific research, and solidly confused about these results, the Dunn Lab has turned this research into a huge citizen science project. This means average joes like you and me can participate. You can submit your own data by sending in belly button swabs to the lab, access all of the data collected, and even give your opinions and present your hypotheses based on your interpretation of the data through online forums and public events.[2]


Get Involved!

  1. Belly Button Biodiversity Project Overview: An overview of the project and links to all sorts of supporting data.
  2. Results and Data: View summarized results and data and download the excel files the researchers use to track specific data like gender, location, belly button type, frequency of washing, and more.
  3. Interactive Data Sets: View pie charts for each individual belly button they’ve sampled so far.
  4. Rob Dunn Lab Home Page: Explore the many projects the Dunn Lab is currently working on.





  1. Sonnenburg, J. (2016, December 7). Frontiers in Human Microbiota Research [Personal interview].
  2. Rob Dunn Lab. (n.d.). Belly Button Biodiversity. Retrieved January 19, 2017, from
  3. Fergus, D. (2013, September 13). The Biggest Microscope in the World–How do We See the Microbiota Around Us? Retrieved January 19, 2017, from
  4. Hulcr, J., Latimer, A. M., Henley, J. B., Rountree, N. R., Fierer, N., Lucky, A., . . . Dunn, R. R. (2012). A Jungle in There: Bacteria in Belly Buttons are Highly Diverse, but Predictable. Retrieved January 19, 2017, from
  5. Fischer, S. (2012, September 14). What Lives in Your Belly Button? Study Finds “Rain Forest” of Species. Retrieved January 19, 2017, from


Banner Photo: 095 by Max Charping  is licensed under CC 2.0