Belly button, navel, umbilicus. Whatever you call it, it’s a source of great scientific inquiry. After reading recently about the Belly Button Biodiversity project, devoted to chronicling the bacterial flora of the belly button, I thought that it’s time to have a repository for the most interesting belly button-related research. Therefore, this post will act as a continuously updated clearinghouse, full of relevant and entertaining navel research. Let’s begin:
– Interested in seeing the diversity of bacteria that grow in your belly button? Then look no further. The Belly Button Biodiversity project (discussed here) has begun compiling data on navel flora, especially for prominent science bloggers.
– Wondering why some belly buttons generate lint and other don’t? Then read The Nature of Navel Fluff by Georg Steinhauser, who explores (using personal experimentation) the hypothesis that abdominal hair increases belly button lint. Here’s the abstract:
Hard facts on a soft matter! In their popular scientific book (Leyner M, Goldberg B. Why do men have nipples – hundreds of questions you’d only ask a doctor after your third martini. New York: Three Rivers Press; 2005), Leyner and Goldberg raised the question why “some belly buttons collect so much lint”. They were, however, not able to come up with a satisfactory answer. The hypothesis presented herein says that abdominal hair is mainly responsible for the accumulation of navel lint, which, therefore, this is a typically male phenomenon. The abdominal hair collects fibers from cotton shirts and directs them into the navel where they are compacted to a felt-like matter. The most abundant individual mass of a piece of lint was found to be between 1.20 and 1.29mg (n=503). However, due to several much larger pieces, the average mass was 1.82mg in this three year study. When the abdominal hair is shaved, no more lint is collected. Old T-shirts or dress shirts produce less navel fuzz than brand new T-shirts. Using elemental analysis, it could be shown that cotton lint contains a certain amount of foreign material, supposedly cutaneous scales, fat or proteins. Incidentally, lint might thus fulfill a cleaning function for the navel.
– Ever thought about why belly buttons appear the way they do? Maybe it’s an evolutionary signal. Or so argues Aki Sinkonnen in the paper Umbilicus as a fitness signal in humans. The author suggests that “the symmetry, shape, and position of umbilicus can be used to estimate the reproductive potential of fertile females.”