November 8, 2012 | David F. Coppedge

Evolutionists Indulge in Navel-Gazing

Sampling bacteria inhabiting our belly buttons sounds like fun, but do the results tell an evolutionary story?

Some science questions might arouse curiosity even if not practically useful.  One of them is “belly button ecology.”  PhysOrg posed the question alongside a cave-like navel: “Ever wonder what’s living in there?”  Some scientists in Florida decided to engage citizens in a survey of their navels.  Their sample is instructive of where the researchers were coming from:

Over the past six months, we have sampled over five hundred volunteers for belly button bacteria. We focus on the first two subsamples (60 individuals in total): a sample from the ScienceOnline meeting of science communicators (January 13–15, 2011, Raleigh, NC, USA), and a sample from the Darwin Day at the Museum of Natural Sciences in Raleigh, NC (February 12, 2011).

[Materials and Methods,  Hulcr J, Latimer AM, Henley JB, Rountree NR, Fierer N, et al. (2012) A Jungle in There: Bacteria in Belly Buttons are Highly Diverse, but Predictable. PLoS ONE 7(11): e47712. doi:10.1371/journal.pone.004771.]

What did they find?  Lots of bacteria.  Archaea were rare, but each navel contained about 67 species on average.  Certain species tended to be more common, forming related clusters called “oligarchs,” but no species was universally found in all  individuals.

A simple experiment like this shows that drawing conclusions is difficult.  Even the simplest observations did not lead to confident conclusions: “Such oligarchs were represented by multiple reads in most sampled human individuals, yet not a single one of the oligarchs is present in all samples.”  What does that mean?  The researchers didn’t control for simple things like lifestyle habits (swimmers vs mud racers), hygiene, sex, age, and other factors, like using other mammals as outgroups.  They just swabbed a few dozen human belly buttons and looked in petri dishes for what turned up.  In addition, they defined a “phylotype” arbitrarily, choosing RNA differences of 3% as diagnostic of species.  What if they had used 2%, or 4%, or 10%?  In addition, they chose to ignore rare species, which might have something to say about the conclusions.  It appears not much more can be said than, “Here are the bacteria that were found in certain individuals’ belly buttons from certain locations at a certain time.”  How would they know whether science teachers and attendees at a Darwin Day event have different navel ecologies than normal people?

The authors appeared eager to attach some evolutionary significance to their results.  One of the team said, “The common, abundant species are from a relatively small number of evolutionary lines, indicating that they have evolved traits that make them at home on human skin.”  That, however, is a statement of ideology, not a conclusion drawn from the data.  It doesn’t really add anything new to evolutionary theory.  Everyone, even creationists, already knows that similar organisms, like orchids, tend to inhabit similar environments.

If we can’t understand evolution by studying data right under our chins, what can evolutionists possibly infer from observations harder to come by?  It’s nice to ask unique questions, and worthwhile to involve “citizen scientists” in research, but this study only serves to reinforce a Law of Evolution and its converse: the more abundant the data, the less storytelling.



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