Why Do We Have Belly Buttons? An Evolutionary Biologist Explains

InnovationScienceWhy Do We Have Belly Buttons? An Evolutionary Biologist ExplainsByScott Travers,Contributor.Forbes contributors publish independent expert analyses and insights. I write about biodiversity and the hidden quirks of the natural world.Follow AuthorJun 11, 2026, 08:30am EDTYour belly button carries nearly 200 million years of evolutionary history — and a thriving microbial ecosystem you’ve probably never thought about.gettyMost people, if asked what their belly button is for, would shrug. The small depression sitting in the middle of their abdomen might seem purposeless, like the body’s own errata. In casual conversation, it’s treated as a biological footnote, something between a quirk and a joke. That’s a semantic shortcut, and it misses almost everything that’s actually interesting about the navel.Your belly button is not a feature of your body. More accurately, it’s a record of it. Specifically, it is possibly the first scar you ever formed: a permanent anatomical annotation of how you came into existence. The question of why we have it is not just anatomical; it’s evolutionary. And the answer reaches back nearly 200 million years, to a reproductive gamble that would eventually produce every dog, whale, bat and human on the planet.Your Belly Button Is A Scar, Not An OrganLet’s start with what the navel actually is. The umbilicus, its clinical name, marks the former attachment point of the umbilical cord, the vascular structure that connected you to the placenta during fetal development. After birth, when the cord is cut and the dried stump detaches, the tissue at the umbilical ring heals over. What remains is a scar, or more specifically, the retracted remnants of four structures:The left umbilical vein (which becomes the round ligament of the liver in adults)The obliterated urachus that runs toward the bladderThe two umbilical arteries that become the medial umbilical ligaments According to a 2019 review in Acta Bio Medica, the navel is, functionall...